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Table of Contents

Basic System Management Commands

Basic System Management Commands

This chapter describes the commands used to perform basic system management tasks, such as naming the router and setting time services.

For basic system management configuration tasks and examples, refer to the chapter entitled "Performing Basic System Management" in the Configuration Fundamentals Configuration Guide.

alias

To create a command alias, use the alias global configuration command. Use the no form of this command to delete all aliases in a command mode or to delete a specific alias, and to revert to the original command syntax.

alias mode alias-name alias-command-line
no alias mode [alias-name]

Syntax Description

mode

Command mode of the original and alias commands. See Table 99 for a list of options for this argument.

alias-name

Command alias.

alias-command-line

Original command syntax.

Defaults

Default aliases are in EXEC mode as follows:
Command Alias Original Command

h

help

lo

logout

p

ping

r

resume

s

show

w

where

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.3.

You can use simple words or abbreviations as aliases. The aliases in the "Defaults" section are predefined. They can be turned off using the no alias command.

Table 99 shows the acceptable options for the mode argument in the alias global configuration command.


Table 99: Mode Argument Options
Argument Options Mode

configuration

Global configuration

controller

Controller configuration

exec

EXEC

hub

Hub configuration

interface

Interface configuration

ipx-router

IPX router configuration

line

Line configuration

map-class

Map class configuration

map-list

Map list configuration

route-map

Route map configuration

router

Router configuration

See the summary of command modes in the "Using the Command Line Interface" chapter in the Configuration Fundamentals Configuration Guide for more information about command modes.

When you use online help, command aliases are indicated by an asterisk (*), as follows:

Router#lo?
*lo=logout    lock    login    logout 

When you use online help, aliases that contain spaces (for example, telnet device.cisco.com 25) are displayed as follows:

Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# alias exec device-mail telnet device.cisco.com 25
Router(config)# end
Router# device-mail?
*device-mail="telnet device.cisco.com 25" 

When you use online help, the alias is expanded and replaced with the original command, as shown in the following example with the td alias:

Router(config)# alias exec td trace device
Router(config)# ^Z
Router# t?
*td="trace device" telnet terminal test tn3270
trace

To list only commands and omit aliases, begin your input line with a space. In the following example, the alias td is not shown, because there is a space before the t? command line.

Router# t?
telnet terminal test tn3270 trace

As with commands, you can use online help to display the arguments and keywords that can follow a command alias. In the following example, the alias td is created to represent the command telet device. The /debug and /line switches can be added to telnet device to modify the command:

Router(config)# alias exec td telnet device
Router(config)# ^Z
Router# td  ?
      /debug     Enable telnet debugging mode
      /line      Enable telnet line mode
            ...
      whois      Whois port
      <cr>
Router# telnet device

You must enter the complete syntax for the alias command. Partial syntax for aliases are not accepted. In the following example, the parser does not recognize the command t as indicating the alias td.

Router# t
% Ambiguous command: "t"

Example

The following example creates the alias fixmyrt for the IP route198.92.116.16:

alias exec fixmyrt clear ip route 198.92.116.16

Related Commands

You can use the master indexes or search online to find documentation of related commands.

show aliases

buffers

Use the buffers global configuration command to make adjustments to initial buffer pool settings and to the limits at which temporary buffers are created and destroyed. Use the no form of this command to return the buffers to their default size.

buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free
| min-free | initial} number
no buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free
| min-free | initial} number

Syntax Description

small

Buffer size of this public buffer pool is 104 bytes.

middle

Buffer size of this public buffer pool is 600 bytes.

big

Buffer size of this public buffer pool is 1524 bytes.

verybig

Buffer size of this public buffer pool is 4520 bytes.

large

Buffer size of this public buffer pool is 5024 bytes.

huge

Default buffer size of this public buffer pool is 18024 bytes. This value can be configured with the buffers huge size command.

type number

Interface type and interface number of the interface buffer pool. The type value cannot be fddi.

permanent

Number of permanent buffers that the system tries to create and keep. Permanent buffers are normally not trimmed by the system.

max-free

Maximum number of free or unallocated buffers in a buffer pool.
A maximum of 20,480 small buffers can be constructed in the pool.

min-free

Minimum number of free or unallocated buffers in a buffer pool.

initial

Number of additional temporary buffers that are to be allocated when the system is reloaded. This keyword can be used to ensure that the system has necessary buffers immediately after reloading in a high-traffic environment.

number

Number of buffers to be allocated.

Default

The default number of buffers in a pool is determined by the hardware configuration and can be displayed with the EXEC show buffers command.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Normally you need not adjust these parameters; do so only after consulting with technical support personnel. Improper settings can adversely impact system performance.

You cannot configure FDDI buffers.

Examples of Public Buffer Pool Tuning

The following example keeps at least 50 small buffers free in the system:

buffers small min-free 50

The following example increases the permanent buffer pool allocation for big buffers to 200:

buffers big permanent 200

Example of Interface Buffer Pool Tuning

A general guideline is to display buffers with the show buffers command, observe which buffer pool is depleted, and increase that one.

The following example increases the permanent Ethernet 0 interface buffer pool on a Cisco 4000 is 96 because the Ethernet 0 buffer pool is depleted:

buffers ethernet 0 permanent 96

Related Commands

You can use the master indexes or search online to find documentation of related commands.

load-interval
show buffers

buffers huge size

Use the buffers huge size global configuration command to dynamically resize all huge buffers to the value you specify. Use the no form of this command to restore the default buffer values.

buffers huge size number
no buffers huge size number

Syntax Description

number

Huge buffer size, in bytes.

Default

18024 bytes

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use only after consulting with technical support personnel. The buffer size cannot be lowered below the default.

Example

The following example resizes huge buffers to 20000 bytes:

buffers huge size 20000

Related Commands

You can use the master indexes or search online to find documentation of related commands.

buffers
show buffers

calendar set

To set the system calendar, use one of the formats of the calendar set EXEC command.

calendar set hh:mm:ss day month year
calendar set hh:mm:ss month day year

Syntax Description

hh:mm:ss

Current time in hours (military format), minutes, and seconds.

day

Current day (by date) in the month.

month

Current month (by name).

year

Current year (no abbreviation).

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted. After you set the calendar, the system clock will be automatically set from the calendar when the system is restarted or when the clock read-calendar EXEC command is issued. The time specified in this command is relative to the configured time zone.

Example

The following example manually sets the system calendar to 1:32 p.m. on July 23, 1997:

calendar set 13:32:00 23 July 1997

Related Commands

You can use the master indexes or search online to find documentation of related commands.

clock read-calendar
clock set
clock summer-time
clock timezone
clock update-calendar

clock calendar-valid

To configure a router as a time source for a network based on its calendar, use the clock calendar-valid global configuration command. Use the no form of this command to specify that the calendar is not an authoritative time source.

clock calendar-valid
no clock calendar-valid

Syntax Description

This command has no arguments or keywords.

Default

The router is not configured as a time source.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted. If you have no outside time source available on your network, use this command to make the calendar an authoritative time source.

Example

The following example configures a router as the time source for a network based on its calendar:

clock calendar-valid

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp master
vines time use-system

clock read-calendar

To manually read the calendar into the system clock, use the clock read-calendar EXEC command.

clock read-calendar

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted. When the router is rebooted, the calendar is automatically read into the system clock. However, you may use this command to manually read the calendar setting into the system clock. This command is useful if the calendar set command has been used to change the setting of the calendar.

Example

The following example configures the system clock to set its date and time by the calendar setting:

clock read-calendar

Related Commands

You can use the master indexes or search online to find documentation of related commands.

calendar set
clock set
clock update-calendar
ntp update-calendar

clock set

To manually set the system clock, use one of the formats of the clock set EXEC command.

clock set hh:mm:ss day month year
clock set hh:mm:ss month day year

Syntax Description

hh:mm:ss

Current time in hours (military format), minutes, and seconds.

day

Current day (by date) in the month.

month

Current month (by name).

year

Current year (no abbreviation).

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Generally, if the system is synchronized by a valid outside timing mechanism, such as an NTP or VINES clock source, or if you have a router with calendar capability, you do not need to set the system clock. Use this command if no other time sources are available. The time specified in this command is relative to the configured time zone.

Example

The following example manually sets the system clock to 1:32 p.m. on July 23, 1997:

clock set 13:32:00 23 July 1997

Related Commands

You can use the master indexes or search online to find documentation of related commands.

calendar set
clock read-calendar
clock summer-time
clock timezone

clock summer-time

To configure the system to automatically switch to summer time (daylight savings time), use one of the formats of the clock summer-time global configuration command. Use the no form of this command to configure the Cisco IOS software not to automatically switch to summer time.

clock summer-time zone recurring [week day month hh:mm week day month hh:mm [offset]]
clock summer-time zone date date month year hh:mm date month year hh:mm [offset]
clock summer-time zone date month date year hh:mm month date year hh:mm [offset]
no clock summer-time

Syntax Description

zone

Name of the time zone (PDT,...) to be displayed when summer time is in effect.

recurring

Indicates that summer time should start and end on the corresponding specified days every year.

date

Indicates that summer time should start on the first specific date listed in the command and end on the second specific date in the command.

week

Week of the month (1 to 5 or last).

day

Day of the week (Sunday, Monday,...).

date

Date of the month (1 to 31).

month

Month (January, February,...).

year

Year (1993 to 2035).

hh:mm

Time (military format) in hours and minutes.

offset

(Optional) Number of minutes to add during summer time (default is 60).

Default

Summer time is disabled. If clock summer-time zone recurring is specified without parameters, the summer time rules default to United States rules. Default of offset is 60.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command if you want to automatically switch to summer time (for display purposes only). Use the recurring form of the command if the local summer time rules are of this form. Use the date form to specify a start and end date for summer time if you cannot use the first form.

In both forms of the command, the first part of the command specifies when summer time begins, and the second part specifies when it ends. All times are relative to the local time zone. The start time is relative to standard time. The end time is relative to summer time. If the starting month is after the ending month, the system assumes that you are in the Southern Hemisphere.

Examples

The following example specifies that summer time starts on the first Sunday in April at 02:00 and ends on the last Sunday in October at 02:00:

clock summer-time PDT recurring 1 Sunday April 2:00 last Sunday October 2:00

If you live in a place where summer time does not follow the pattern in the first example, you could set it to start on October 12, 1997 at 02:00, and end on April 26, 1998 at 02:00, with the following example:

clock summer-time date 12 October 1997 2:00 26 April 1998 2:00

Related Commands

You can use the master indexes or search online to find documentation of related commands.

calendar set
clock timezone

clock timezone

To set the time zone for display purposes, use the clock timezone global configuration command. To set the time to Coordinated Universal Time (UTC), use the no form of this command.

clock timezone zone hours [minutes]
no clock timezone

Syntax Description

zone

Name of the time zone to be displayed when standard time is in effect.

hours

Hours offset from UTC.

minutes

(Optional) Minutes offset from UTC.

Default

UTC

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

The system internally keeps time in UTC, so this command is used only for display purposes and when the time is manually set.

Example

The following example sets the timezone to Pacific Standard Time and offsets 8 hours behind UTC:

clock timezone PST -8

Related Commands

You can use the master indexes or search online to find documentation of related commands.

calendar set
clock set
clock summer-time
show clock

clock update-calendar

To set the calendar from the system clock, use the clock update-calendar EXEC command.

clock update-calendar

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted.

If the system clock and calendar are not synchronized, and the system clock is more accurate, use this command to update the calendar to the correct date and time.

Example

The following example copies the current time from the system clock to the calendar:

clock update-calendar

Related Commands

You can use the master indexes or search online to find documentation of related commands.

clock read-calendar
ntp update-calendar

downward-compatible-config

To generate a configuration that is compatible with an earlier Cisco IOS release, use the downward-compatible-config global configuration command. To remove this feature, use the no form of this command.

downward-compatible-config version
no downward-compatible-config

Syntax Description

version

Cisco IOS Release number, not earlier than 10.2.

Default

Disabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.1.

In Cisco IOS Release 10.3, IP access lists changed format. Use this command to regenerate a configuration in a format prior to Release 10.3 if you are going to downgrade from a Release 10.3 or later to an earlier release. The earliest release this command accepts is 10.2.

When this command is configured, the router attempts to generate a configuration that is compatible with the specified version. Currently, this command affects only IP access lists.

Under some circumstances, the software might not be able to generate a fully backward-compatible configuration. In such a case, the software issues a warning message.

Example

The following example generates a configuration file compatible with Cisco  IOS Release 10.2:

downward-compatible-config 10.2

Related Commands

You can use the master indexes or search online to find documentation of related commands.

access-list (extended)
access-list (standard)

hostname

To specify or modify the host name for the network server, use the hostname global configuration command. The host name is used in prompts and default configuration filenames. The setup command facility also prompts for a host name at startup.

hostname name

Syntax Description

name

New host name for the network server.

Default

The factory-assigned default host name is router.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

The order of display at startup is banner message-of-the-day (MOTD), then login and password prompts, then EXEC banner.

Do not expect case to be preserved. Upper- and lowercase characters look the same to many internet software applications (often under the assumption that the application is doing you a favor). It may seem appropriate to capitalize a name the same way you might do in English, but conventions dictate that computer names appear all lowercase. For more information, refer to RFC 1178, Choosing a Name for Your Computer.

The name must also follow the rules for ARPANET host names. They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphens. Names must be 63 characters or fewer. For more information, refer to RFC  1035, Domain Names---Implementation and Specification.

Example

The following example changes the host name to sandbox:

hostname sandbox

Related Commands

You can use the master indexes or search online to find documentation of related commands.

setup

ip bootp server

To access the BOOTP service available from hosts on the network, use the ip bootp server global configuration command. Use the no form of the command to disable these services.

ip bootp server
no ip bootp server

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

By default, the BOOTP server is enabled.

When you disable the BOOTP server, access to the BOOTP ports cause the Cisco IOS software to send an "ICMP port unreachable" message to the sender and discard the original incoming packet.


Note Unlike defaults for other commands, this command will display when you perform show running config to display current settings, whether or not you have changed the default using the no  ip bootp server command.

Example

The following example disables the BOOTP service on the router:

no ip bootp server

ip telnet source-interface

Use the ip telnet source-interface global configuration command to allow a user to select an address of an interface as the source address for Telnet connections. Use the no form of this command to reset the source address to the default for each connection.

ip telnet source-interface interface
no ip telnet source-interface

Syntax Description

interface

The interface whose address is to be used as the source for Telnet connections.

Default

The address of the closest interface to the destination as the source address. If the selected interface is not "up," the Cisco IOS software selects the address of the closest interface to the destination as the source address.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.1.

Use this command to set an interface's IP address as the source for all Telnet connections.

Example

The following example makes the IP address for Ethernet interface 1 as the source address for Telnet connections:

ip telnet source-interface e 1

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ip tacacs source-interface
ip tftp source-interface
ip radius source-interface

ip tftp source-interface

Use the ip tftp source-interface global configuration command to allow a user to select the interface whose address will be used as the source address for TFTP connections.

ip tftp source-interface interface
no ip tftp source-interface

Syntax Description

interface

The interface whose address is to be used as the source for TFTP connections.

Default

The address of the closest interface to the destination as the source address. If the selected interface is not "up," the Cisco IOS software selects the address of the closest interface to the destination as the source address.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.1.

Use this command to set an interface's IP address as the source for all TFTP connections.

Example

The following example makes the IP address for Ethernet interface 1 as the source address for TFTP connections:

ip tftp source-interface e 1

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ip radius source-interface
ip tacacs source-interface
ip telnet source-interface

load-interval

To change the length of time for which data is used to compute load statistics, use the load-interval interface configuration command. Use the no form of this command to revert to the default setting.

load-interval seconds
no load-interval seconds

Syntax Description

seconds

Length of time for which data is used to compute load statistics. A value that is a multiple of 30, from 30 to 600 (30, 60, 90, 120, and so forth).

Default

300 seconds (or 5 minutes)

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.3.

If you want load computations to be more reactive to short bursts of traffic, rather than averaged over 5-minute periods, you can shorten the length of time over which load averages are computed.

If the load interval is set to 30 seconds, new data is used for load calculations over a 30-second period. This data is used to compute load statistics, including input rate in bits and packets per second, output rate in bits and packets per second, load, and reliability.

Load data is gathered every 5 seconds. This data is used for a weighted average calculation in which more-recent load data has more weight in the computation than older load data. If the load interval is set to 30 seconds, the average is computed for the last 30 seconds of load data.

The load-interval command allows you to change the default interval of 5 minutes to a shorter or longer period of time. If you change it to a shorter period of time, the input and output statistics that are displayed when you use the show interface command will be more current, and based on more instantaneous data, rather than reflecting a more average load over a longer period of time.

This command is often used for dial backup purposes, to increase or decrease the likelihood of a backup interface being implemented, but it can be used on any interface.

Example

In the following example, the default 5-minute average is set it to a 30-second average. A burst in traffic that would not trigger a dial backup for an interface configured with the default 5-minute interval might trigger a dial backup for this interface that is set for a shorter, 30-second interval.

interface serial 0
  load-interval 30

Related Commands

You can use the master indexes or search online to find documentation of related commands.

show interfaces

ntp access-group

To control access to the system's Network Time Protocol (NTP) services, use the ntp access-group global configuration command. To remove access control to the system's NTP services, use the no form of this command.

ntp access-group {query-only | serve-only | serve | peer} access-list-number
no ntp access-group {query-only | serve-only | serve | peer}

Syntax Description

query-only

Allows only NTP control queries. See RFC 1305 (NTP version 3).

serve-only

Allows only time requests.

serve

Allows time requests and NTP control queries, but does not allow the system to synchronize to the remote system.

peer

Allows time requests and NTP control queries and allows the system to synchronize to the remote system.

access-list-number

Number (1 to 99) of a standard IP access list.

Default

No access control (full access granted to all systems)

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

The access group options are scanned in the following order from least restrictive to most restrictive:

    1. peer

    2. serve

    3. serve-only

    4. query-only

Access is granted for the first match that is found. If no access groups are specified, all access is granted to all sources. If any access groups are specified, only the specified access is granted. This facility provides minimal security for the time services of the system. However, it can be circumvented by a determined programmer. If tighter security is desired, use the NTP authentication facility.

Example

The following example configures the system to allow itself to be synchronized by a peer from access list 99. However, the system restricts access to allow only time requests from access list 42.

ntp access-group peer 99
ntp access-group serve-only 42

Related Commands

You can use the master indexes or search online to find documentation of related commands.

access-list

ntp authenticate

To enable Network Time Protocol (NTP) authentication, use the ntp authenticate global configuration command. Use the no form of this command to disable the feature.

ntp authenticate
no ntp authenticate

Syntax Description

This command has no arguments or keywords.

Default

No authentication

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command if you want authentication. If this command is specified, the system will not synchronize to a system unless it carries one of the authentication keys specified in the ntp trusted-key command.

Example

The following example configures the system to synchronize only to systems providing authentication key 42 in its NTP packets:

ntp authenticate
ntp authentication-key 42 md5 aNiceKey
ntp trusted-key 42

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp authentication-key
ntp trusted-key

ntp authentication-key

To define an authentication key for Network Time Protocol (NTP), use the ntp authentication-key global configuration command. Use the no form of this command to remove the authentication key for NTP.

ntp authentication-key number md5 value
no ntp authentication-key number

Syntax Description

number

Key number (1 to 4294967295).

md5

Authentication key. Message authentication support is provided using the Message Digest (MD5) algorithm. The key type md5 is currently the only key type supported.

value

Key value (an arbitrary string of up to eight characters).

Default

No authentication key is defined for NTP.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command to define authentication keys for use with other NTP commands in order to provide a higher degree of security.


Note When this command is written to NVRAM, the key is encrypted so that it is not displayed when the configuration is viewed.

Example

The following example configures the system to synchronize only to systems providing authentication key 42 in its NTP packets:

ntp authenticate
ntp authentication-key 42 md5 aNiceKey
ntp trusted-key 42

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp authenticate
ntp peer
ntp server
ntp trusted-key

ntp broadcast

To specify that a specific interface should send Network Time Protocol (NTP) broadcast packets, use the ntp broadcast interface configuration command. Use the no form of this command to disable this capability.

ntp broadcast [version number]
no ntp broadcast

Syntax Description

version number

(Optional) Number from 1 to 3 indicating the NTP version.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Example

The following example configures Ethernet interface 0 to send NTP version 2 packets:

interface ethernet 0
  ntp broadcast version 2

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp broadcast client
ntp broadcastdelay

ntp broadcast client

To allow the system to receive NTP broadcast packets on an interface, use the ntp broadcast client interface configuration command. Use the no form of this command to disable this capability.

ntp broadcast client
no ntp broadcast client

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command to allow the system to listen to broadcast packets on an interface-by-interface basis.

Example

The following example synchronizes the Cisco IOS software to NTP packets broadcast on Ethernet interface 1:

interface ethernet 1
  ntp broadcast client

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp broadcast
ntp broadcastdelay

ntp broadcastdelay

To set the estimated round-trip delay between the Cisco IOS software and a Network Time Protocol (NTP) broadcast server, use the ntp broadcastdelay global configuration command. Use the no form of this command to revert to the default value.

ntp broadcastdelay microseconds
no ntp broadcastdelay

Syntax Description

microseconds

Estimated round-trip time (in microseconds) for NTP broadcasts. The range is from 1 to 999999.

Default

3000 microseconds

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command when the router is configured as a broadcast client and the round-trip delay on the network is other than 3000 microseconds.

Example

The following example sets the estimated round-trip delay between a router and the broadcast client to 5000 microseconds:

ntp broadcastdelay 5000

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp broadcast
ntp broadcast client

ntp clock-period

Caution Do not enter this command; it is documented for informational purposes only. The system automatically generates this command as Network Time Protocol (NTP) determines the clock error and compensates.

As NTP compensates for the error in the system clock, it keeps track of the correction factor for this error. The system automatically saves this value into the system configuration using the ntp  clock-period global configuration command. The system uses the no form of this command to revert to the default.

ntp clock-period value
no ntp clock-period

Syntax Description

value

Amount to add to the system clock for each clock hardware tick (in units of
2
-32 seconds).

Default

17179869 2-32 seconds (4 milliseconds)

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

If a copy running-config startup-config command is entered to save the configuration to NVRAM, this command will automatically be added to the configuration. It is a good idea to perform this task after NTP has been running for a week or so; this will help NTP synchronize more quickly if the system is restarted.

ntp disable

To prevent an interface from receiving Network Time Protocol (NTP) packets, use the ntp disable interface configuration command. To enable receipt of NTP packets on an interface, use the no form of this command.

ntp disable
no ntp disable

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

This command provides a simple method of access control.

Example

The following example prevents Ethernet interface 0 from receiving NTP packets:

interface ethernet 0
  ntp disable

ntp master

To configure the Cisco IOS software as a Network Time Protocol (NTP) master clock to which peers synchronize themselves when an external NTP source is not available, use the ntp master global configuration command. To disable the master clock function, use the no form of this command.

ntp master [stratum]
no ntp master [stratum]
Caution Use this command with extreme caution. It is very easy to override valid time sources using this command, especially if a low stratum number is configured. Configuring multiple machines in the same network with the ntp master command can cause instability in keeping time if the machines do not agree on the time.

Syntax Description

stratum

(Optional) Number from 1 to 15. Indicates the NTP stratum number that the system will claim.

Default

By default, the master clock function is disabled. When enabled, the default stratum is 8.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Because Cisco's implementation of NTP does not support directly attached radio or atomic clocks, the router is normally synchronized, directly or indirectly, to an external system that has such a clock. In a network without Internet connectivity, such a time source may not be available. The ntp  master command is used in such cases.

If the system has ntp master configured, and it cannot reach any clock with a lower stratum number, the system will claim to be synchronized at the configured stratum number, and other systems will be willing to synchronize to it via NTP.


Note The system clock must have been set from some source, including manually, before ntp  master will have any effect. This protects against distributing erroneous time after the system is restarted.

Example

The following example configures a router as an NTP master clock to which peers may synchronize:

ntp master 10

Related Commands

You can use the master indexes or search online to find documentation of related commands.

clock calendar-valid

ntp peer

To configure the system clock to synchronize a peer or to be synchronized by a peer, use the
ntp peer global configuration command. To disable this capability, use the no form of this command.

ntp peer ip-address [version number] [key keyid] [source interface] [prefer]
no ntp peer ip-address

Syntax Description

ip-address

IP address of the peer providing, or being provided, the clock synchronization.

version

(Optional) Defines the Network Time Protocol (NTP) version number.

number

(Optional) NTP version number (1 to 3).

key

(Optional) Defines the authentication key.

keyid

(Optional) Authentication key to use when sending packets to this peer.

source

(Optional) Names the interface.

interface

(Optional) Name of the interface from which to pick the IP source address.

prefer

(Optional) Makes this peer the preferred peer that provides synchronization.

Default

No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command if you want to allow this machine to synchronize with the peer, or vice versa. Using the prefer keyword reduces switching back and forth between peers.

If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version number 2. Many NTP servers on the Internet run version 2.

Example

The following example configures a router to allow its system clock to be synchronized with the clock of the peer (or vice versa) at IP address 192.168.22.33 using NTP version 2. The source IP address is the address of Ethernet 0.

ntp peer 192.168.22.33 version 2 source ethernet 0

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp authentication-key
ntp server
ntp source

ntp server

To allow the system clock to be synchronized by a time server, use the ntp server global configuration command. To disable this capability, use the no form of this command.

ntp server ip-address [version number] [key keyid] [source interface] [prefer]
no ntp server ip-address

Syntax Description

ip-address

IP address of the time server providing the clock synchronization.

version

(Optional) Defines the Network Time Protocol (NTP) version number.

number

(Optional) NTP version number (1 to 3).

key

(Optional) Defines the authentication key.

keyid

(Optional) Authentication key to use when sending packets to this peer.

source

(Optional) Identifies the interface from which to pick the IP source address.

interface

(Optional) Name of the interface from which to pick the IP source address.

prefer

(Optional) Makes this server the preferred server that provides synchronization.

Default

No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command if you want to allow this machine to synchronize with the specified server. The server will not synchronize to this machine.

Using the prefer keyword reduces switching back and forth between servers.

If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version number 2. Many NTP servers on the Internet run version 2.

Example

The following example configures a router to allow its system clock to be synchronized with the clock of the peer at IP address 172.16.22.44 using NTP version 2:

ntp server 172.16.22.44 version 2

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp authentication-key
ntp peer
ntp source

ntp source

To use a particular source address in Network Time Protocol (NTP) packets, use the ntp source global configuration command. Use the no form of this command to remove the specified source address.

ntp source type number
no ntp source

Syntax Description

type

Type of interface.

number

Number of the interface.

Default

Source address is determined by the outgoing interface.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use this command when you want to use a particular source IP address for all NTP packets. The address is taken from the named interface. This command is useful if the address on an interface cannot be used as the destination for reply packets. If the source keyword is present on an ntp server or ntp peer command, that value overrides the global value.

Example

The following example configures a router to use the IP address of Ethernet 0 as the source address of all outgoing NTP packets:

ntp source ethernet 0

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp peer
ntp server

ntp trusted-key

To authenticate the identity of a system to which Network Time Protocol (NTP) will synchronize, use the ntp trusted-key global configuration command. Use the no form of this command to disable authentication of the identity of the system.

ntp trusted-key key-number
no ntp trusted-key key-number

Syntax Description

key-number

Key number of authentication key to be trusted.

Default

Disabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

If authentication is enabled, use this command to define one or more key numbers (corresponding to the keys defined with the ntp authentication-key command) that a peer NTP system must provide in its NTP packets, in order for this system to synchronize to it. This provides protection against accidentally synchronizing the system to a system that is not trusted, since the other system must know the correct authentication key.

Example

The following example configures the system to synchronize only to systems providing authentication key 42 in its NTP packets:

ntp authenticate
ntp authentication-key 42 md5 aNiceKey
ntp trusted-key 42

Related Commands

You can use the master indexes or search online to find documentation of related commands.

ntp authenticate
ntp authentication-key

ntp update-calendar

To periodically update the calendar from Network Time Protocol (NTP), use the ntp update-calendar global configuration command. Use the no form of this command to disable the periodic updates.

ntp update-calendar
no ntp update-calendar

Syntax Description

This command has no arguments or keywords.

Default

The calendar is not updated.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted.

If a router is synchronized to an outside time source via NTP, it is a good idea to periodically update the calendar with the time learned from NTP. Otherwise, the calendar will tend to gradually lose or gain time. The calendar will be updated only if NTP has synchronized to an authoritative time server.

Example

The following example configures the system to periodically update the calendar from the system clock:

ntp update-calendar

Related Commands

You can use the master indexes or search online to find documentation of related commands.

clock read-calendar
clock update-calendar

prompt

To customize the prompt, use the prompt global configuration command. To revert to the default prompt, use the no form of this command.

prompt string
no prompt [string]

Syntax Description

string

Prompt. It can consist of all printing characters and the escape sequences listed in Table 100.

Default

The default prompt is either Router or the name defined with the hostname global configuration command, followed by an angle bracket (>) for EXEC mode or a pound sign (#) for privileged EXEC mode.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.3.

You can include escape sequences when specifying the prompt. All escape sequences are preceded by a percent sign (%). Table 100 lists the valid escape sequences.


Table 100: Custom Prompt Escape Sequences
Escape Sequence Interpretation

%h

Host name. This is either Router or the name defined with the hostname global configuration command.

%n

Physical terminal line (TTY) number of the EXEC user.

%p

Prompt character itself. It is either an angle bracket (>) for EXEC mode or a pound sign (#) for privileged EXEC mode.

%s

Space.

%t

Tab.

%%

Percent sign (%)

Issuing the prompt %h command has the same effect as issuing the no prompt command.

Examples

The following example changes the EXEC prompt to include the TTY number, followed by the name and a space:

prompt TTY%n@%h%s%p

The following are examples of user and privileged EXEC prompts that result from the previous command:

TTY17@Router1 >
TTY17SRouter1 #

Related Commands

You can use the master indexes or search online to find documentation of related commands.

hostname

scheduler allocate

To guarantee CPU time for processes, use the scheduler allocate global configuration command on the Cisco 7200 series and Cisco 7500 series. The no form of this command restores the default.

scheduler allocate interrupt-time process-time
no scheduler allocate

Syntax Description

interrupt-time

Integer (in microseconds) that limits the maximum number of microseconds to spend on fast switching within any one network interrupt context. The range is 400 to 60000 microseconds. The default is 4000 microseconds.

process-time

Integer (in microseconds) that guarantees the minimum number of microseconds to spend at the process level when network interrupts are disabled. The range is 100 to 4000. The default is 200 microseconds.

Default

Approximately 5 percent of the CPU is available for process tasks.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

This command applies to the Cisco 7200 series and Cisco 7500 series.

Caution Cisco recommends that you do not change the default values.

Example

The following example makes 20 percent of the CPU available for process tasks:

scheduler allocate 2000 500

Related Commands

You can use the master indexes or search online to find documentation of related commands.

scheduler interval

scheduler interval

To control the maximum amount of time that can elapse without running system processes, use the scheduler interval global configuration command. The no form of this command restores the default.

scheduler interval milliseconds
no scheduler interval

Syntax Description

milliseconds

Integer that specifies the interval, in milliseconds. The minimum interval that you can specify is 500 milliseconds; there is no maximum value.

Default

High-priority operations are allowed to use as much of the central processor as needed.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

The normal operation of the network server allows the switching operations to use as much of the central processor as is required. If the network is running unusually heavy loads that do not allow the processor the time to handle the routing protocols, give priority to the system process scheduler. High-priority operations are allowed to use as much of the central processor as needed.

On the Cisco 7200 series and Cisco 7500 series, use the scheduler allocate global configuration command.

Example

The following example changes the low-priority process schedule to an interval of 750 milliseconds:

scheduler interval 750

Related Commands

You can use the master indexes or search online to find documentation of related commands.

scheduler allocate

service decimal-tty

To specify that line numbers be displayed and interpreted as decimal numbers rather than octal numbers, use the service decimal-tty global configuration command. Use the no form of this command to restore the default.

service decimal-tty
no service decimal-tty

Syntax Description

This command has no arguments or keywords.

Default

Decimal numbers on the 500-CS and Cisco 2500 Series.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Example

The following example displays decimal rather than octal line numbers:

service decimal-tty

service exec-wait

To delay the startup of the EXEC on noisy lines, use the service exec-wait global configuration command. Use the no form of this command to disable the delay function.

service exec-wait
no service exec-wait

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

This command delays startup of the EXEC until the line has been idle (no traffic seen) for 3 seconds. The default is to enable the line immediately on modem activation.

This command is useful on noisy modem lines or when a modem attached to the line is configured to ignore MNP or V.42 negotiations, and MNP or V.42 modems may be dialing in. In these cases, noise or MNP/V.42 packets may be interpreted as usernames and passwords, causing authentication failure before the user gets a chance to type a username/password. The command is not useful on non-modem lines or lines without some kind of login configured.

Example

The following example delays the startup of the EXEC:

service exec-wait

service finger

To allow Finger protocol requests (defined in RFC 742) to be made of the network server, use the service finger global configuration command. This service is equivalent to issuing a remote show  users command. Use the no form of this command to remove this service.

service finger
no service finger

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Example

The following example disables the Finger protocol:

no service finger

service hide-telnet-address

To hide addresses while trying to establish a Telnet session, use the service hide-telnet-address global configuration command. Use the no form of this command to remove this service.

service hide-telnet-address
no service hide-telnet-address

Syntax Description

This command has no arguments or keywords.

Default

Addresses are displayed.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

When you attempt to connect to a device, the router displays addresses and other messages (for example, Trying router1 (171.69.1.154, 2008)...). With the hide feature, the router suppresses the display of the address (for example, Trying router1 address #1...). The router continues to display all other messages that would normally display during a connection attempt, such as detailed error messages if the connection was not successful.

The hide feature improves the functionality of the busy-message feature. When you configure only the busy-message command, the normal messages generated during a connection attempt are not displayed; only the busy-message is displayed. When you use the hide and busy features together you can customize the information displayed during Telnet connection attempts. When you configure the service hide-telnet-address command and the busy-message command, the router suppresses the address and displays the message specified with the busy-message command if the connection attempt is not successful.

Example

The following example hides Telnet addresses:

service hide-telnet-address

Related Commands

You can use the master indexes or search online to find documentation of related commands.

busy-message

service nagle

To enable the Nagle congestion control algorithm, use the service nagle global configuration command. Use the no form of this command to disable the algorithm.

service nagle
no service nagle

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

When using a standard TCP implementation to send keystrokes between machines, TCP tends to send one packet for each keystroke typed. On larger networks, many small packets use up bandwidth and contribute to congestion.

John Nagle's algorithm (RFC 896) helps alleviate the small-packet problem in TCP. In general, it works this way: The first character typed after connection establishment is sent in a single packet, but TCP holds any additional characters typed until the receiver acknowledges the previous packet. Then the second, larger packet is sent, and additional typed characters are saved until the acknowledgment comes back. The effect is to accumulate characters into larger chunks, and pace them out to the network at a rate matching the round-trip time of the given connection. This method is usually a good for all TCP-based traffic. However, do not use the service nagle command if you have XRemote users on X Window sessions.

Example

The following example enables the Nagle algorithm:

service nagle

service prompt config

To display the configuration prompt (config), use the service prompt config global configuration command. Use the no form of this command to remove the configuration prompt.

service prompt config
no service prompt config

Syntax Description

This command has no arguments or keywords.

Default

The configuration mode prompts (hostname(config)#) appear in all configuration modes.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.1.

Example

In the following example, the no service prompt config command prevents the configuration prompt from being displayed. The prompt is still displayed in EXEC mode. When the service prompt config command is entered, the configuration mode prompt reappears.

Router# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# no service prompt config
hostname bob
end
bob# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
service prompt config
bob(config)# hostname Router
Router(config)# end
Router#

Related Commands

You can use the master indexes or search online to find documentation of related commands.

hostname
prompt

service tcp-small-servers

To access minor TCP/IP services available from hosts on the network, use the service tcp-small-servers global configuration command. Use the no form of the command to disable these services.

service tcp-small-servers
no service tcp-small-servers

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.1.

By default, the TCP servers for Echo, Discard, Chargen, and Daytime services are enabled.

When you disable the minor TCP/IP servers, access to the Echo, Discard, Chargen, and Daytime ports cause the Cisco IOS software to send a TCP RESET packet to the sender and discard the original incoming packet.


Note Unlike defaults for other commands, this command will display when you perform show running config to display current settings whether or not you have changed the default using the no  service tcp-small-servers command.

Example

The following example enables minor TCP/IP services available from the network:

service tcp-small-servers

service telnet-zero-idle

To set the TCP window to zero (0) when the Telnet connection is idle, use the service telnet-zero-idle global configuration command. Use the no form of this command to disable this service.

service telnet-zero-idle
no service telnet-zero-idle

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Normally, data sent to noncurrent Telnet connections is accepted and discarded. When service telnet-zero-idle is enabled, if a session is suspended (that is, some other connection is made active or the EXEC is sitting in command mode), the TCP window is set to zero. This action prevents the remote host from sending any more data until the connection is resumed. Use this command when it is important that all messages sent by the host be seen by the users and the users are likely to use multiple sessions.

Do not use this command if your host will eventually time out and log out a TCP user whose window is zero.

Example

The following example sets the TCP window to zero when the Telnet connection is idle:

service telnet-zero-idle

Related Commands

You can use the master indexes or search online to find documentation of related commands.

resume

service udp-small-servers

To access minor User Datagram Protocol (UDP) services available from hosts on the network, use the service udp-small-servers global configuration command. Use the no form of the command to disable these services.

service udp-small-servers
no service udp-small-servers

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

By default the UPD servers for Echo, Discard, and Chargen services are enabled.

When you disable the servers, access to Echo, Discard, and Chargen ports causes the Cisco IOS software to send an "ICMP port unreachable" message to the sender and discard the original incoming packet.


Note Unlike defaults for other commands, this command will display when you perform show running config to display current settings, whether or not you have changed the default using the no  service udp-small-servers command.

Example

The following example disables minor UDP services on the router:

no service udp-small-servers

show aliases

To display all alias commands, or the alias commands in a specified mode, use the show aliases EXEC command.

show aliases [mode]

Syntax Description

mode

(Optional) Command mode. See Table 99 in the description of the alias command for acceptable options for the mode argument.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.3.

All of the modes listed in Table 99 have their own prompts, except for the null interface mode. For example, the prompt for interface configuration mode is Router(config-if).

Sample Display

The following is sample output from the show aliases exec commands. The aliases configured for commands in EXEC mode are displayed.

Router# show aliases exec
Exec mode aliases:
    h                                        help
    lo                                      logout
    p                                        ping
    r                                        resume
    s                                        show
    w                                        where

Related Commands

You can use the master indexes or search online to find documentation of related commands.

alias

show buffers

Use the show buffers EXEC command to display statistics for the buffer pools on the network server.

show buffers [type number | alloc [dump]]

Syntax Description

type number

(Optional) Displays interface pool information. If the specified interface type and number has its own buffer pool, displays information for that pool. Value of type can be ethernet, serial, tokenring, fddi, bri, atm, e1, t1.

alloc

(Optional) Displays a brief listing of all allocated buffers.

dump

(Optional) Dumps all allocated buffers. This keyword must be used with the alloc keyword, not by itself.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Sample Displays

The following is sample output from the show buffers command with no arguments, showing all buffer pool information:

Router# show buffers
Buffer elements:
     398 in free list (500 max allowed)
     1266 hits, 0 misses, 0 created
 
Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50):
     50 in free list (20 min, 150 max allowed)
     551 hits, 0 misses, 0 trims, 0 created
Middle buffers, 600 bytes (total 25, permanent 25):
     25 in free list (10 min, 150 max allowed)
     39 hits, 0 misses, 0 trims, 0 created
Big buffers, 1524 bytes (total 50, permanent 50):
     49 in free list (5 min, 150 max allowed)
     27 hits, 0 misses, 0 trims, 0 created
VeryBig buffers, 4520 bytes (total 10, permanent 10):
     10 in free list (0 min, 100 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Large buffers, 5024 bytes (total 0, permanent 0):
     0 in free list (0 min, 10 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Huge buffers, 18024 bytes (total 0, permanent 0):
     0 in free list (0 min, 4 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
          
Interface buffer pools:
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Ethernet1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing0 buffers, 4516 bytes (total 48, permanent 48):
     0 in free list (0 min, 48 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing1 buffers, 4516 bytes (total 32, permanent 32):
     32 in free list (0 min, 48 max allowed)
     16 hits, 0 fallbacks
0 failures (0 no memory)

Table 101 describes significant fields shown in the display.


Table 101: Show Buffers Field Descriptions
Field Description

Buffer elements

Buffer elements are small structures used as placeholders for buffers in internal operating system queues. Buffer elements are used when a buffer may need to be on more than one queue.

free list

Total number of the currently unallocated buffer elements.

max allowed

Maximum number of buffers that are available for allocation.

hits

Count of successful attempts to allocate a buffer when needed.

misses

Count of buffer allocation attempts that resulted in growing the buffer pool
to allocate a buffer.

created

Count of new buffers created to satisfy buffer allocation attempts when the available buffers in the pool have already been allocated.

Public buffer pools:

 Small buffers

Buffers that are 104 bytes long.

   Middle buffers

Buffers that are 600 bytes long.

 Big buffers

Buffers that are 1524 bytes long.

 VeryBig buffers

Buffers that are 4520 bytes long.

 Large buffers

Buffers that are 5024 bytes long.

 Huge buffers

Buffers that are 18024 bytes long.

   total

Total number of this type of buffer.

   permanent

Number of these buffers that are permanent.

   free list

Number of available or unallocated buffers in that pool.

   min

Minimum number of free or unallocated buffers in the buffer pool

   max allowed

Maximum number of free or unallocated buffers in the buffer pool

   hits

Count of successful attempts to allocate a buffer when needed.

   misses

Count of buffer allocation attempts that resulted in growing the buffer pool in order to allocate a buffer.

   trims

Count of buffers released to the system because they were not being used. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static.

   created

Count of new buffers created in response to misses. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static.

Interface buffer pools:

   total

Total number of this type of buffer.

   permanent

Number of these buffers that are permanent.

   free list

Number of available or unallocated buffers in that pool.

   min

Minimum number of free or unallocated buffers in the buffer pool.

   max allowed

Maximum number of free or unallocated buffers in the buffer pool.

   hits

Count of successful attempts to allocate a buffer when needed.

   fallbacks

Count of buffer allocation attempts that resulted in falling back to the public buffer pool that is the smallest pool at least as big as the interface buffer pool.

   max cache size

Maximum number of buffers from that interface's pool that can be in that interface buffer pool's cache. Each interface buffer pool has its own cache. These are not additional to the permanent buffers; they come from the interface's buffer pools. Some interfaces place all of their buffers from the interface pool into the cache. In this case, it is normal for the free list to display  0.

failures

Total number of allocation requests that have failed because no buffer was available for allocation; the datagram was lost. Such failures normally occur at interrupt level.

no memory

Number of failures that occurred because no memory was available to create a new buffer.

The following is sample output from the show buffers command with an interface type and number:

Router# show buffers Ethernet 0
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache

The following is sample output from the show buffers command when alloc is specified:

Router# show buffers alloc
Buffer elements:
     398 in free list (500 max allowed)
     1266 hits, 0 misses, 0 created
 
Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50):
     50 in free list (20 min, 150 max allowed)
     551 hits, 0 misses, 0 trims, 0 created
Middle buffers, 600 bytes (total 25, permanent 25):
     25 in free list (10 min, 150 max allowed)
     39 hits, 0 misses, 0 trims, 0 created
Big buffers, 1524 bytes (total 50, permanent 50):
     49 in free list (5 min, 150 max allowed)
     27 hits, 0 misses, 0 trims, 0 created
VeryBig buffers, 4520 bytes (total 10, permanent 10):
     10 in free list (0 min, 100 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Large buffers, 5024 bytes (total 0, permanent 0):
     0 in free list (0 min, 10 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Huge buffers, 18024 bytes (total 0, permanent 0):
     0 in free list (0 min, 4 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
          
Interface buffer pools:
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Ethernet1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing0 buffers, 4516 bytes (total 48, permanent 48):
     0 in free list (0 min, 48 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing1 buffers, 4516 bytes (total 32, permanent 32):
     32 in free list (0 min, 48 max allowed)
     16 hits, 0 fallbacks
0 failures (0 no memory)
Address    PakAddr    Data          Off  Data    Pool    Ref  Link  Enc          Flags  Output    Input
                                    Area          set  Size                Cnt  Type  Type        (Hex)  Idb          Idb
--------------------------------------------------------------------------------
604B37A0 604B37C0 40004A38    62    60 Big     1   65    3        0 Et0          
604C6DA0 604C6DC0 40007038    84     0 Ether   1    0    0        0              
604C6F60 604C6F80 400076E4    84     0 Ether   1    0    0        0              
604C7120 604C7140 40007D90    84     0 Ether   1    0    0        0              
604C72E0 604C7300 4000843C    84     0 Ether   1    0    0        0              
604C74A0 604C74C0 40008AE8    84     0 Ether   1    0    0        0              
604C7660 604C7680 40009194    84     0 Ether   1    0    0        0              
604C7820 604C7840 40009840    84     0 Ether   1    0    0        0              
.
.
.

show calendar

To display the calendar hardware setting, use the show calendar EXEC command:

show calendar

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted.

You can compare the time and date shown with this command with the time and date listed via the show clock command to verify that the calendar and system clock are in sync with each other. The time displayed is relative to the configured time zone.

Sample Display

In the following sample display, the hardware calendar indicates the timestamp of 12:13:44 p.m. on Friday, July 19, 1996:

Router# show calendar
12:13:44 PST Fri Jul 19 1996

Related Commands

You can use the master indexes or search online to find documentation of related commands.

show clock

show clock

To display the system clock, use the show clock EXEC command.

show clock [detail]

Syntax Description

detail

(Optional) Indicates the clock source (NTP, VINES, system calendar, and so forth) and the current summer-time setting (if any).

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

The system clock keeps an "authoritative" flag that indicates whether the time is authoritative (believed to be accurate). If the system clock has been set by a timing source (system calendar, NTP, VINES, and so forth), the flag is set. If the time is not authoritative, it will be used only for display purposes. Until the clock is authoritative and the "authoritative" flag is set, the flag prevents peers from synchronizing to the clock when the peers' time is invalid.

The symbol that precedes the show clock display indicates the following:
Symbol Description

*

Time is not authoritative.

(blank)

Time is authoritative.

.

Time is authoritative, but NTP is not synchronized.

Sample Display

The following sample output shows that the current clock is authoritative and that the time source is NTP:

Router# show clock detail
15:29:03.158 PST Mon Mar 3 1997
Time source is NTP

Related Commands

You can use the master indexes or search online to find documentation of related commands.

clock set
show calendar

show ntp associations

To show the status of Network Time Protocol (NTP) associations, use the show ntp associations EXEC command.

show ntp associations [detail]

Syntax Description

detail

(Optional) Shows detailed information about each NTP association.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Sample Displays

Detailed descriptions of the information displayed by this command can be found in the NTP specification (RFC 1305).

The following is sample output from the show ntp associations command:

Router# show ntp associations
     address         ref clock     st    when    poll    reach    delay    offset        disp
  ~172.31.32.2      172.31.32.1       5    29    1024    377     4.2   -8.59     1.6
+~192.168.13.33    192.168.1.111     3    69      128    377     4.1    3.48     2.3
*~192.168.13.57    192.168.1.111     3    32      128    377     7.9   11.18     3.6
* master (synced), # master (unsynced), + selected, - candidate, ~ configured

Table 102 describes significant fields shown in the display.


Table 102: Show NTP Associations Field Descriptions
Field Description

(leading characters in display lines)

The first characters in a display line can be one or more of the following characters:

*        Synchronized to this peer

#        Almost synchronized to this peer

+        Peer selected for possible synchronization

-        Peer is a candidate for selection

~        Peer is statically configured

address

Address of peer.

ref clock

Address of peer's reference clock.

st

Peer's stratum.

when

Time since last NTP packet received from peer.

poll

Polling interval (seconds).

reach

Peer reachability (bit string, in octal).

delay

Round-trip delay to peer (milliseconds).

offset

Relative time of peer's clock to local clock (milliseconds).

disp

Dispersion

The following is sample output of the show ntp associations detail command:

Router# show ntp associations detail
172.31.32.2 configured, insane, invalid, stratum 5
ref ID 172.31.32.1, time AFE252C1.6DBDDFF2 (00:12:01.428 PDT Mon Jul 5 1993)
our mode active, peer mode active, our poll intvl 1024, peer poll intvl 64
root delay 137.77 msec, root disp 142.75, reach 376, sync dist 215.363
delay 4.23 msec, offset -8.587 msec, dispersion 1.62
precision 2**19, version 3
org time AFE252E2.3AC0E887 (00:12:34.229 PDT Mon Jul 5 1993)
rcv time AFE252E2.3D7E464D (00:12:34.240 PDT Mon Jul 5 1993)
xmt time AFE25301.6F83E753 (00:13:05.435 PDT Mon Jul 5 1993)
filtdelay =     4.23    4.14    2.41    5.95    2.37    2.33    4.26    4.33
filtoffset =   -8.59   -8.82   -9.91   -8.42    -10.51    -10.77    -10.13    -10.11
filterror =     0.50    1.48    2.46    3.43    4.41    5.39    6.36    7.34
192.168.13.33 configured, selected, sane, valid, stratum 3
ref ID 192.168.1.111, time AFE24F0E.14283000 (23:56:14.078 PDT Sun Jul 4 1993)
our mode client, peer mode server, our poll intvl 128, peer poll intvl 128
root delay 83.72 msec, root disp 217.77, reach 377, sync dist 264.633
delay 4.07 msec, offset 3.483 msec, dispersion 2.33
precision 2**6, version 3
org time AFE252B9.713E9000 (00:11:53.442 PDT Mon Jul 5 1993)
rcv time AFE252B9.7124E14A (00:11:53.441 PDT Mon Jul 5 1993)
xmt time AFE252B9.6F625195 (00:11:53.435 PDT Mon Jul 5 1993)
filtdelay =     6.47    4.07    3.94    3.86    7.31    7.20    9.52    8.71
filtoffset =    3.63    3.48    3.06    2.82    4.51    4.57    4.28    4.59
filterror =     0.00    1.95    3.91    4.88    5.84    6.82    7.80    8.77
192.168.13.57 configured, our_master, sane, valid, stratum 3
ref ID 192.168.1.111, time AFE252DC.1F2B3000 (00:12:28.121 PDT Mon Jul 5 1993)
our mode client, peer mode server, our poll intvl 128, peer poll intvl 128
root delay 125.50 msec, root disp 115.80, reach 377, sync dist 186.157
delay 7.86 msec, offset 11.176 msec, dispersion 3.62
precision 2**6, version 2
org time AFE252DE.77C29000 (00:12:30.467 PDT Mon Jul 5 1993)
rcv time AFE252DE.7B2AE40B (00:12:30.481 PDT Mon Jul 5 1993)
xmt time AFE252DE.6E6D12E4 (00:12:30.431 PDT Mon Jul 5 1993)
filtdelay =    49.21    7.86    8.18    8.80    4.30    4.24    7.58    6.42
filtoffset =   11.30   11.18   11.13   11.28    8.91    9.09    9.27    9.57
filterror =     0.00    1.95    3.91    4.88    5.78    6.76    7.74    8.71   

Table 103 describes significant fields shown in the display.


Table 103: Show NTP Associations Detail Field Descriptions
Field Descriptions

configured

Peer was statically configured.

dynamic

Peer was dynamically discovered.

our_master

Local machine is synchronized to this peer.

selected

Peer is selected for possible synchronization.

candidate

Peer is a candidate for selection.

sane

Peer passes basic sanity checks.

insane

Peer fails basic sanity checks.

valid

Peer time is believed to be valid.

invalid

Peer time is believed to be invalid.

leap_add

Peer is signaling that a leap second will be added.

leap-sub

Peer is signaling that a leap second will be subtracted.

unsynced

Peer is not synchronized to any other machine.

ref ID

Address of machine peer is synchronized to.

time

Last timestamp peer received from its master.

our mode

Our mode relative to peer (active / passive / client / server / bdcast / bdcast client).

peer mode

Peer's mode relative to us.

our poll intvl

Our poll interval to peer.

peer poll intvl

Peer's poll interval to us.

root delay

Delay along path to root (ultimate stratum 1 time source).

root disp

Dispersion of path to root.

reach

Peer reachability (bit string in octal).

sync dist

Peer synchronization distance.

delay

Round trip delay to peer.

offset

Offset of peer clock relative to our clock.

dispersion

Dispersion of peer clock.

precision

Precision of peer clock in Hz.

version

NTP version number that peer is using.

org time

Originate time stamp.

rcv time

Receive time stamp.

xmt time

Transmit time stamp.

filtdelay

Round trip delay in milliseconds of each sample.

filtoffset

Clock offset in milliseconds of each sample.

filterror

Approximate error of each sample.

Related Commands

You can use the master indexes or search online to find documentation of related commands.

show ntp status

show ntp status

To show the status of Network Time Protocol (NTP), use the show ntp status EXEC command.

show ntp status

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Sample Display

The following is sample output from the show ntp status command:

Router# show ntp status
Clock is synchronized, stratum 4, reference is 192.168.13.57
nominal freq is 250.0000 Hz, actual freq is 249.9990 Hz, precision is 2**19
reference time is AFE2525E.70597B34 (00:10:22.438 PDT Mon Jul 5 1993)
clock offset is 7.33 msec, root delay is 133.36 msec
root dispersion is 126.28 msec, peer dispersion is 5.98 msec

Table 104 shows the significant fields in the display.


Table 104: Show NTP Status Field Descriptions
Field Description

synchronized

System is synchronized to an NTP peer.

unsynchronized

System is not synchronized to any NTP peer.

stratum

NTP stratum of this system.

reference

Address of peer we are synchronized to.

nominal freq

Nominal frequency of system hardware clock.

actual freq

Measured frequency of system hardware clock.

precision

Precision of this system's clock (in Hz).

reference time

Reference timestamp.

clock offset

Offset of our clock to synchronized peer.

root delay

Total delay along path to root clock.

root dispersion

Dispersion of root path.

peer dispersion

Dispersion of synchronized peer.

Related Commands

You can use the master indexes or search online to find documentation of related commands.

show ntp associations

show sntp

Use the show sntp EXEC command on a Cisco  1003, Cisco  1004, or Cisco  1005 router to show information about the Simple Network Time Protocol (SNTP).

show sntp

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Sample Display

The following is sample output from the show sntp command:

Router# show sntp
SNTP server     Stratum   Version    Last Receive
171.69.118.9       5         3        00:01:02 
172.21.28.34       4         3        00:00:36    Synced  Bcast
Broadcast client mode is enabled.

Table 105 describes the fields show in this display.


Table 105: Show SNTP Field Descriptions
Field Description

SNTP server

Address of the configured or broadcast NTP server.

Stratum

NTP stratum of the server. The stratum indicates how far away from an authoritative time source the server is.

Version

NTP version of the server.

Last Receive

Time since the last NTP packet was received from the server.

Synced

Indicates the server chosen for synchronization.

Bcast

Indicates a broadcast server.

Related Commands

You can use the master indexes or search online to find documentation of related commands.

sntp broadcast client
sntp server

sntp broadcast client

Use the sntp broadcast client global configuration command to configure a Cisco  1003, Cisco  1004, or Cisco  1005 router to use the Simple Network Time Protocol (SNTP) to accept Network Time Protocol (NTP) traffic from any broadcast server. The no form of the command prevents the router from accepting broadcast traffic.

sntp broadcast client
no sntp broadcast client

Syntax Description

This command has no arguments or keywords.

Default

The router does not accept SNTP traffic from broadcast servers.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

SNTP is a compact, client-only version of the Network Time Protocol (NTP). SNMP can only receive the time from NTP servers; it cannot be used to provide time services to other systems.

SNTP typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex filtering and statistical mechanisms of NTP. In addition, SNTP does not authenticate traffic, although you can configure extended access lists to provide some protection.

You must configure the router with either this command or the sntp server command in order enable SNTP.

Example

The following example enables the router to accept broadcast NTP packets and shows sample show sntp command output:

Router(config)# sntp broadcast client
Router(config)# end
Router# 
%SYS-5-CONFIG: Configured from console by console
Router# show sntp
SNTP server     Stratum   Version    Last Receive
172.21.28.34       4         3        00:00:36    Synced  Bcast
Broadcast client mode is enabled.

Related Commands

You can use the master indexes or search online to find documentation of related commands.

show sntp
sntp server

sntp server

Use the sntp server global configuration command to configure a Cisco  1003, Cisco  1004, or Cisco  1005 router to use the Simple Network Time Protocol (SNTP) to request and accept Network Time Protocol (NTP) traffic from a time server. The no form of the command removes a server from the list of NTP servers.

sntp server {address | hostname} [version number]
no sntp server {address | hostname}

Syntax Description

address

IP address of the time server.

hostname

Hostname of the time server.

version number

(Optional) Version of NTP to use. The default is 1.

Default

The router does not accept SNTP traffic from a time server.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

SNTP is a compact, client-only version of the Network Time Protocol (NTP). SNMP can only receive the time from NTP servers; it cannot be used to provide time services to other systems.

SNTP typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex filtering and statistical mechanisms of NTP. In addition, SNTP does not authenticate traffic, although you can configure extended access lists to provide some protection.

Enter this command once for each NTP server.

You must configure the router with either this command or the sntp broadcast client command in order enable SNTP.

Example

The following example enables the router to request and accept NTP packets from the server at 172.21.118.9 and shows sample show sntp command output:

Router(config)# sntp server 172.21.118.9
Router(config)# end
Router# 
%SYS-5-CONFIG: Configured from console by console
Router# show sntp
SNTP server     Stratum   Version    Last Receive
172.21.118.9       5         3        00:01:02        Synced 

Related Commands

You can use the master indexes or search online to find documentation of related commands.

show sntp
sntp broadcast client


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