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Media-Independent PPP and Multilink PPP Commands

Media-Independent PPP and Multilink PPP Commands

This chapter describes the commands available to configure the Point-to-Point Protocol (PPP) for dial-up wide-area networking on your router.

For information about configuring PPP on Cisco routers, see the "Configuring Media-Independent PPP and Multilink PPP" chapter in the Dial Solutions Configuration Guide.

For information about configuring PPP on asynchronous links, refer to the "Configuring SLIP and PPP" chapter in the Dial Solutions Configuration Guide. For PPP commands for asynchronous links, refer to the "SLIP and PPP Commands" chapter in the Dial Solutions Command Reference.

For more information about PPP, see RFC 1661. For more information about MLP, see RFC 1717. For more information about PAP, see RFC 1334. For more information about CHAP, see RFC 1994.

compress

To configure software compression for Point-to-Point Protocol (PPP) encapsulation, use the ppp compress interface configuration command. To disable compression, use the no form of this command.

compress [predictor | stac | mppc [ignore-pfc]]
no compress [predictor | stac | mppc [ignore-pfc]]

Syntax Description

ignore-pfc

(Optional) Specifies that the protocol field compression flag negotiated through LCP will be ignored.

mppc

(Optional) Specifies that the MPPC compression algorithm will be used.

predictor

(Optional) Specifies that a predictor compression algorithm will be used.

stac

(Optional) Specifies that a Stacker (LZS) compression algorithm will be used.

Default

PPP compression is disabled.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.
The mppc and ignore-pfc options first appeared in Cisco IOS Release 11.3 T.

End-point devices must be configured to use the same compression method (predictor, Stacker or MPPC).

Compression reduces the size of frames via lossless data compression. The compression algorithm used is a predictor algorithm (the RAND compression algorithm), which uses a compression dictionary to predict what the next character in the frame will be.

PPP encapsulation supports both predictor and Stacker compression algorithms.

MPPC Compression

The compress command using the mppc and ignore-pfc options support compression between Cisco routers and access servers and Microsoft clients, such as Windows 95 and Windows NT. MPPC implements an LZ based compression algorithm that uses a compression dictionary to compress PPP packets. The ignore-pfc keyword instructs the router to ignore the protocol field compression flag negotiated by LCP. For example, the uncompressed standard protocol field value for IP is 0x0021 and 0x21 when compression is enabled. When the ignore-pfc option is enabled, the router will continue to use the uncompressed value (0x0021). Using the ignore-pfc option is helpful for some asynchronous driver devices which use an uncompressed protocol field (0x0021), even though the pfc is negotiated between peers. If protocol rejects are displayed when the debug ppp negotiation command is enabled, setting the ignore-pfc option may remedy the problem.

System performance

Compression is performed in software and may significantly affect system performance. We recommend that you disable compression if CPU load exceeds 65 percent. To display the CPU load, use the show process cpu EXEC command.

You should never enable compression for connections to a public data network.

If the majority of your traffic is already compressed files, we recommend that you not use compression. If the files are already compressed, the additional processing time spent in attempting unsuccessfully to compress them again will slow system performance.

Examples

The following example enables predictor compression on serial interface 0:

interface serial 0
  encapsulation ppp
  compress predictor

The following example configures BRI interface 0 to perform MPPC:

interface BRI0
  ip unnumbered ethernet0
  encapsulation ppp
  isdn spid1 5551234
  dialer map ip 172.21.71.74 5551234
  dialer-group 1
  compress mppc

The following example configures asynchronous interface 1 to implement MPPC and ignore the protocol field compression flag negotiated by LCP:

interface async1
  ip unnumbered ethernet0
  encapsulation ppp
  async default routing
  async dynamic routing
  async mode interactive
  peer default ip address 172.21.71.74
  compress mppc ignore-pfc

Related Commands

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

encapsulation ppp
show compress

encapsulation ppp

To set the Point-to-Point Protocol (PPP) as the encapsulation method used by a serial or ISDN interface, use the encapsulation ppp interface configuration command. Use the no form of this command to disable PPP encapsulation.

encapsulation ppp
no encapsulation ppp

Syntax Description

This command has no arguments or keywords.

Default

HDLC on synchronous serial interfaces

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in a release prior to Cisco IOS Release 10.0.

To use PPP encapsulation, the router must be configured with an IP routing protocol.

Example

The following example enables PPP encapsulation on serial interface 0:

interface serial 0
 encapsulation ppp

Related Commands

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

keepalive
ppp
ppp authentication

ip address-pool

To enable an address pooling mechanism used to supply IP addresses to dial-in asynchronous, synchronous, or ISDN point-to-point interfaces, use the ip address-pool global configuration command. To disable IP address pooling globally on all interfaces with the default configuration, use the no form of the command.

ip address-pool [dhcp-proxy-client | local]
no ip address-pool

Syntax Description

dhcp-proxy-client

(Optional) Uses the router as the proxy-client between a third-party Dynamic Host Configuration Protocol (DHCP) server and peers connecting to the router.

local

(Optional) Uses the local address pool named default.

Default

IP address pooling is disabled.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.0.

The global default mechanism applies to all interfaces that have been left in the default setting of the peer default ip address pool command.

If any peer default ip address command other than peer default ip address pool (the default) is configured, then the interface uses that mechanism and not the global default mechanism. Thus all interfaces can be independently configured or left unconfigured so that the global default mechanism setting apply. This flexibility minimizes the configuration effort on the part of the administrator.

Examples

The following example specifies the DHCP proxy client mechanism as the global default mechanism for assigning peer IP addresses:

ip address-pool dhcp-proxy-client

The following example specifies a local IP address pool called default as the global default mechanism for all interfaces that have been left in their default setting:

ip address-pool local

Related Commands

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

encapsulation ppp
encapsulation slip

ip dhcp-server
ip local pool
member peer default ip address
peer default ip address
peer default ip address pool
ppp

show dhcp
show ip local pool
slip

ip dhcp-server

To specify which Dynamic Host Configuration Protocol (DHCP) servers to use on your network, specify the IP address of one or more DHCP servers available on the network, use the ip dhcp-server global configuration command. Use the no form of the command to remove a DHCP server's IP address.

ip dhcp-server [ip-address | name]
no ip dhcp-server [ip-address | name]

Syntax Description

ip-address

(Optional) IP address of a DHCP server.

name

(Optional) Name of a DHCP server.

Default

The IP limited broadcast address of 255.255.255.255 is used for transactions if no DHCP server is specified. This allows automatic detection of DHCP servers.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.0.

A DHCP server temporarily allocates network addresses to clients through the access server on an as-needed basis. While the client is active, the address is automatically renewed in a minimum of 20-minute increments. When the user terminates the session, the interface connection is terminated so that network resources can be quickly reused. You can specify up to ten servers on the network.

In normal situations, if a user's SLIP/PPP session fails (for example if a modem line disconnects), the allocated address will be reserved temporarily to preserve the same IP address for the client when dialed back into the server. This way, the session that was accidentally terminated can often be resumed.

To use the DHCP proxy-client feature, enable your access server to be a proxy-client on asynchronous interfaces by using the ip address-pool dhcp-proxy-client command. If you wish to specify which DHCP servers are used on your network, use the ip dhcp-server command to define up to ten specific DHCP servers.


Note To facilitate transmission, configure intermediary routers (or access servers with router functionality) to use an IP helper address whenever the DHCP server is not on the local LAN and the access server is using broadcasts to interact with the DHCP server. See "Configuring IP Addressing" in the Network Protocols Configuration Guide, Part 1.

The ip address-pool dhcp-proxy-client command initializes proxy-client status to all interfaces defined as asynchronous on the access server. To selectively disable proxy-client status on a single asynchronous interface, use the no peer default ip address interface command.

Example

The following command specifies a DHCP server with the IP address of 129.12.13.81:

ip dhcp-server 129.12.13.81

Related Commands

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

ip address-pool dhcp-proxy-client
ip helper address

peer default ip address pool
show dhcp

ip local pool

To configure a local pool of IP addresses to be used when a remote peer connects to a point-to-point interface, use the ip local pool global configuration command. To delete an address pool, use the no form of this command.

ip local pool {default | pool-name low-ip-address [high-ip-address]}
no ip local pool {default | poolname}

Syntax Description

default

Default local address pool that is used if no other pool is named.

pool-name

Name of a specific local address pool.

low-ip-address

Lowest IP address in the pool.

high-ip-address

(Optional) Highest IP address in the pool. If this value is omitted only the low-ip-address IP address is included in the local pool. The maximum number of IP addresses per pool is 256.

Default

No address pools are configured.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.0.

Use the ip local pool command to create one or more local address pools from which IP addresses are assigned when a peer connects. The default address pool is then used on all point-to-point interfaces after the ip address-pool local global configuration command is issued. To use a specific, named address pool on an interface, use the peer default ip address pool interface configuration command.

These pools can also be used with the translate commands for one-step vty-async connections and in certain AAA/TACACS+ authorization functions. Refer to the "Configuring Protocol Translation and Virtual Asynchronous Devices" chapter in the Dial Solutions Configuration Guide and the "System Management" part of the Configuration Fundamentals Configuration Guide for more information. Pools can be displayed with the show ip local pool command.

Example

The following command creates a local IP address pool by the name of quark, which contains all local IP addresses from 172.16.23.0 to 172.16.23.255:

ip local pool quark 172.16.23.0 172.16.23.255 

Related Commands

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

ip address-pool
show ip local pool

ip rtp reserve

To reserve a special queue for a set of Real-time Transport Protocol (RTP) packet flows belonging to a range of UDP destination ports, use the ip rtp reserve interface configuration command. To disable the special queue for real-time traffic, use the no form of the command.

ip rtp reserve lowest-udp-port range-of-ports [maximum-bandwidth]
no rtp reserve

Syntax Description

lowest-udp-port

Lowest UDP port number to which the packets are sent.

range-of-ports

Number, which added to the lowest-UDP-port value, yields the highest UDP port value.

maximum-bandwidth

(Optional) Bandwidth, in kilobits per second, reserved for the RTP packets to be sent to the specified UDP ports.

Default

This function is disabled by default. No default values are provided for the arguments.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Release 11.3.

If the bandwidth needed for RTP packet flows exceeds the maximum bandwidth specified, the reserved queue will degrade to a best-effort queue.

This command helps in improving the delay bounds of voice streams by giving them a higher priority.

Example

The following example reserves a unique queue for traffic to destination UDP ports in the range 32768 to 32788 and reserves 1,000 kbps bandwidth for that traffic:

ip rtp reserve 32768 20 1000

Related Commands

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

ppp multilink
ppp multilink fragment-delay
ppp multilink interleave

multilink virtual-template

To specify a virtual template from which the specified Multilink PPP bundle interface can clone its interface parameters, use the multilink virtual-template global configuration command.

multilink virtual-template number

Syntax Description

number

Number of the virtual template; an integer in the range 1  through  9.

Default

Disabled. No template number is defined.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

MLP virtual templates require that an IP address be defined for the remote client.

Example

The following example specifies an MLP virtual template to be used and then defines the template to be applied to an MLP bundle interface:

multilink virtual-template 1
ip local pool default 2.2.2.2
interface virtual-template 1
 ip unnumbered ethernet 0
 encapsulation ppp
 ppp multilink 
 ppp authentication chap

Related Commands

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

interface virtual-template
ip local pool

peer default ip address

Use the peer default ip address interface configuration command to specify an IP address, an address from a specific IP address pool, or an address from the DHCP mechanism to be returned to a remote peer connecting to this interface. Use the no form of the command to disable a prior peer IP address pooling configuration on an interface.

peer default ip address {ip-address | dhcp | pool [pool-name]}
no peer default ip address

Syntax Description

ip-address

Specific IP address to be assigned to a remote peer dialing in to the interface. To prevent duplicate IP addresses from being assigned on more than one interface, this command argument cannot be applied to a dialer rotary group nor to an ISDN interface.

dhcp

Retrieve an IP address from the DHCP server.

pool

Use the global default mechanism as defined by the ip address-pool command unless the optional pool-name argument is supplied. This is the default.

pool-name

(Optional) Name of a local address pool created using the ip local pool command. Retrieve an address from this pool regardless of the global default mechanism setting.

Default

pool

Command Mode

Interface configuration

Usage Guidelines

This command applies to point-to-point interfaces that support the PPP or SLIP encapsulation.

This command allows an administrator to configure all possible address pooling mechanisms on a interface-by-interface basis.

The peer default ip address command can override the global default mechanism defined by the ip address-pool command on an interface-by-interface basis.

Examples

The following command specifies that this interface will use a local IP address pool called pool3:

peer default ip address pool pool3

The following command specifies that this interface will use the IP address 172.140.34.21:

peer default ip address 172.140.34.21

The following command reenables the global default mechanism to be used on this interface:

peer default ip address pool

Related Commands

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

encapsulation ppp
encapsulation slip
ip address-pool
ip dhcp-server
ip local pool
ppp
slip

show dhcp

peer neighbor-route

To reenable the creation of peer neighbor routes on an interface once this default behavior has been disabled, use the peer neighbor-route interface configuration command. To disable the default behavior of creating a neighbor route for the peer on a point-to-point interface, use the no form of this command.

peer neighbor-route
no peer neighbor-route

Syntax Description

This command has no keywords and arguments.

Default

Creation of a route to the peer address on any point-to-point interface when the PPP IPCP negotiation is completed.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Use the no form of this command only if the default behavior creates problems in your network environment.

If you enter this command on a dialer interface or a async-group interface, it affects all member interfaces.

Example

The following examples reenables the default behavior on an interface.

peer neighbor-route 

ppp authentication

To specify the order in which the CHAP or PAP protocols are requested on the interface, use the ppp authentication interface configuration command. Use the no form of the command to disable this authentication.

ppp authentication {chap | chap pap | pap chap | pap} [if-needed] [list-name | default]
[callin]

no ppp authentication

Syntax Description

chap

Enables CHAP on a serial interface.

pap

Enables PAP on a serial interface.

chap pap

Enables both CHAP and PAP, and performs CHAP authentication before PAP.

pap chap

Enables both CHAP and PAP, and performs PAP authentication before CHAP.

if-needed

(Optional) Used with TACACS and XTACACS. Do not perform CHAP or PAP authentication if the user has already provided authentication. This option is available only on asynchronous interfaces.

list-name

(Optional) Used with AAA/TACACS+. Specifies the name of a list of TACACS+ methods of authentication to use. If no list name is specified, the system uses the default. Lists are created with the aaa authentication ppp command.

default

(Optional) Used with AAA/TACACS+. Created with the aaa authentication ppp command.

callin

(Optional) Specifies authentication on incoming (received) calls only.

Default

PPP authentication is not enabled.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in a release prior to Cisco IOS Release 11.1.

Once you have enabled CHAP or PAP authentication or both, the local router requires the remote device to prove its identity before allowing data traffic to flow.

You may enable PAP or CHAP or both, in either order. If both methods are enabled, then the first method specified will be requested during link negotiation. If the peer suggests using the second method or simply refuses the first method, then the second method will be tried. Some remote devices support CHAP only and some PAP only. The order in which you specify the methods will be based on your concerns about the remote device's ability to correctly negotiate the appropriate method as well as your concern about data line security. PAP usernames and passwords are sent as "clear-text" strings and can be intercepted and reused. CHAP has eliminated most of the known security holes.

Enabling or disabling PPP authentication does not affect the local router's willingness to authenticate itself to the remote device.

Caution If you use a list-name that has not been configured with the aaa authentication ppp command, you disable PPP on this line.

Example

The following example enables CHAP on asynchronous interface 4, and uses the authentication list MIS-access:

interface async 4
 encapsulation ppp
 ppp authentication chap MIS-access

Related Commands

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

aaa authentication ppp
aaa new-model
autoselect
dialer map
encapsulation ppp
ppp use-tacacs
username password

ppp bridge appletalk

To enable half-bridging of AppleTalk packets across a serial interface, use the ppp bridge appletalk interface configuration command. Use the no form of this command to disable AppleTalk packet half-bridging.

ppp bridge appletalk
no ppp bridge appletalk

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 11.2.

When you configure a serial or ISDN interface for half bridging, you configure it to function as a node on an Ethernet subnetwork. It communicates with a bridge on the subnetwork by sending and receiving bridge packets. The serial or ISDN interface converts bridge packets to routed packets and forwards them, as needed.

The serial interface must be configured with an AppleTalk address for communication on the Ethernet subnetwork, and the AppleTalk address must have the same AppleTalk cable range as the bridge.

You cannot configure a serial interface for both half-bridging and for transparent bridging.

No more than one half-bridge should be on any subnetwork.

Example

The following example configures serial interface 0 for half-bridging of AppleTalk. The remote bridge and other Ethernet nodes must be on the same network.

interface serial 0
 ppp bridge appletalk
 appletalk cable-range 301-301
 appletalk zone remote-lan

Related Commands

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

appletalk cable-range
appletalk zone
ppp bridge ip
ppp bridge ipx

ppp bridge ip

To enable half-bridging of IP packets across a serial interface, use the ppp bridge ip interface configuration command. Use the no form of this command to disable IP packet half-bridging.

ppp bridge ip
no ppp bridge ip

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 11.2.

When you configure a serial or ISDN interface for half-bridging, you configure it to function as a node on an Ethernet subnetwork. It communicates with a bridge on the subnetwork by sending and receiving bridge packets. The serial interface converts bridge packets to routed packets and forwards them, as needed.

The interface must be configured with an IP address for communication on the Ethernet subnetwork, and the IP address must be on the same subnetwork as the bridge.

You cannot configure a serial interface for both half-bridging and for transparent bridging.

No more than one half-bridge should be on any subnetwork.

Example

The following example configures serial interface 0 for half-bridging of IP. The remote bridge and other Ethernet nodes must be on the same subnetwork.

interface serial 0
  ip address 172.69.5.8
  ppp bridge ip

Related Commands

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

ip address
ppp bridge appletalk
ppp bridge ipx

ppp bridge ipx

To enable half-bridging of IPX packets across a serial interface, use the ppp bridge ipx interface configuration command. Use the no form of this command to return to novell-ether encapsulation.

ppp bridge ipx [novell-ether | arpa | sap | snap]
no ppp bridge ipx

Syntax Description

novell-ether

(Optional) Use Novell's Ethernet_802.3 encapsulation. This is the default.

arpa

(Optional) Use Novell's Ethernet_II encapsulation.

sap

(Optional) Use Novell's Ethernet_802.2 encapsulation.

snap

(Optional) Use Novell Ethernet_Snap encapsulation.

Default

Default encapsulation is novell-ether.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

When you configure a serial interface for half bridging, you configure it to function as a node on an Ethernet subnetwork. It communicates with a bridge on the subnetwork by sending and receiving bridge packets. The serial interface converts bridge packets to routed packets and forwards them, as needed.

The serial interface must be configured with an IPX address for communication on the Ethernet subnetwork, and the IPX address must be on the same subnetwork as the bridge.

You cannot configure a serial interface for both half-bridging and for transparent bridging.

No more than one half-bridge should be on any subnetwork.

Example

The following example configures serial interface 0 for half-bridging of IPX. The remote bridge and other Ethernet nodes must be on the same subnetwork.

interface serial 0
  ppp bridge ipx 
  ipx network 1800

Related Commands

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

ipx network
ppp bridge appletalk
ppp bridge ip

ppp chap hostname

Use the ppp chap hostname interface configuration command to create a pool of dialup routers that all appear to be the same host when authenticating with CHAP. To disable this function, use the no form of the command.

ppp chap hostname hostname
no ppp chap hostname hostname

Syntax Description

hostname

Name to be sent in the CHAP challenge.

Default

Disabled. The router name is sent in any CHAP challenges.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Currently, a router dialing a pool of access routers requires a username entry for each possible router in the pool because each router challenges with its hostname. If a router is added to the dialup rotary pool, all connecting routers must be updated. The ppp chap hostname command allows you to specify a common alias for all routers in a rotary to use so that only one username must be configured on the dialing routers.

This command is normally used with local CHAP authentication (when authenticating to the peer), but it will also be used for remote CHAP authentication.

Example

The commands in the following example identify the dialer interface 0 as the dialer rotary group leader and specifies ppp as the method of encapsulation used by all member interfaces. Authentication is by CHAP on received calls only. The username ISPCorp will be sent in all CHAP challenges and responses.

interface dialer 0
 encapsulation ppp
 ppp authentication chap callin
 ppp chap hostnmae ISPCorp

Related Commands

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

aaa authentication ppp
ppp authentication
ppp chap password
ppp pap

ppp chap password

To configure a common CHAP secret to be used in responses to challenges from an unknown remote peer in a collection of routers that do not support this command (such as routers running older Cisco  IOS software images), use the ppp chap password interface configuration command. To disable this function, use the no form of this command.

ppp chap password secret
no ppp chap password secret

Syntax Description

secret

Secret used to compute the response value for any CHAP challenge from an unknown peer.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

This command allows you to replace several username and password configuration commands with a single copy of this command on any dialer interface or asynchronous group interface.

This command is used for remote CHAP authentication only (when authenticating to the peer) and does not affect local CHAP authentication.

Example

The following example configures interface BRI 0 for PPP encapsulation. If a CHAP challenge is received from a peer whose name is not found in the global list of usernames, the encrypted secret 7  1234567891 is decrypted and used to create a CHAP response value.

interface bri0
 encapsulation ppp
 ppp chap password 7 1234567891 

Related Commands

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

aaa authentication ppp
ppp authentication
ppp chap hostname
ppp pap

ppp max-bad-auth

To configure a point-to-point interface not to reset itself immediately after an authentication failure but instead to allow a specified number of authentication retries, use the ppp max-bad-auth interface configuration command. To reset to the default of immediate reset, use the no form of this command.

ppp max-bad-auth number
no ppp max-bad-auth

Syntax Description

number

Number of retries after which the interface is to reset itself. Default is 0.

Default

0

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

This command applies to any serial interface (asynchronous serial, synchronous serial, or ISDN) on which PPP encapsulation is enabled.

Example

The following example sets BRI interface 0 to allow two additional retries after an initial authentication failure (for a total of three failed authentication attempts):

interface bri 0
 encapsulation ppp
 ppp authentication chap 
 ppp max-bad-auth 3

Related Commands

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

encapsulation ppp

ppp multilink

To enable Multilink PPP on an interface, use the ppp multilink interface configuration command. To disable Multilink PPP, use the no form of this command.

ppp multilink
no ppp multilink

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 11.1.

Multilink PPP is designed to work over single or multiple interfaces that are configured to support both dial-on-demand rotary groups and PPP encapsulation. This command applies asynchronous serial interfaces, ISDN Basic Rate Interfaces (BRIs), and ISDN Primary Rate Interfaces (PRIs).

PPP compression is allowed with MLP.

Multilink PPP and PPP reliable link do not work together.

The dialer load-threshold command is used to enable a rotary group to bring up additional links and to add them to a multilink bundle.

When multilink PPP is configured, dialer-load threshold 1 command no longer keeps a multilink bundle of n links connected indefinitely and the dialer-load threshold 2 command no longer keeps a multilink bundle of 2 links connected indefinitely. If you want a multilink bundle to be connected indefinitely, you must set a very high idle timer.

Example

The following partial example configures a dialer for Multilink PPP; it does not show the configuration of the physical interfaces.

interface Dialer0
  ip address 99.0.0.2 255.0.0.0
  encapsulation ppp
  dialer in-band
  dialer idle-timeout 500
  dialer map ip 99.0.0.1 name atlanta broadcast 81012345678901
  dialer load-threshold 30 either
  dialer-group 1
  ppp authentication chap
  ppp multilink

Related Commands

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

dialer-group
dialer idle-timeout

dialer load-threshold
encapsulation ppp
ppp authentication
compress

ppp multilink fragment-delay

To configure a maximum delay allowed for transmission of a packet fragment on a Multilink PPP bundle, use the ppp multilink fragment-delay interface configuration command. To reset the maximum delay to the default value, use the no form of the command.

ppp multilink fragment-delay milliseconds
no ppp multilink fragment-delay

Syntax Description

milliseconds

Maximum delay, in milliseconds, allowed for any packet fragment. Default is 30  milliseconds.

Default

This command is disabled by default.

Default delay is 30 milliseconds.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.3.

The ppp multilink fragment-delay command applies only to interfaces that can configure a bundle interface. These include virtual-templates, dialer interfaces, and ISDN BRI or PRI interfaces.

Multilink PPP chooses a fragment size based on the maximum delay allowed. If real-time traffic requires a certain maximum bound on delay, using this command to set that maximum delay can ensure that a real-time packet will get interleaved within the fragments of a large packet.

Example

The following example requires a voice to have a maximum bound on delay of 20  milliseconds:

ppp multilink fragment-delay 20 

Related Commands

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

ip rtp reserve
ppp multilink
ppp multilink interleave

ppp multilink interleave

To enable interleaving of Real-Time Transport Protocol (RTP) packets among the fragments of larger packets on a Multilink PPP bundle, use the ppp multilink interleave interface configuration command. To disable interleaving, use the no form of the command.

ppp multilink interleave
no ppp multilink interleave

Syntax Description

This command has no arguments and keywords.

Default

This function is disabled by default.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Release 11.3.

The ppp multilink interleave command applies only to interfaces that can configure a bundle interface. These include virtual-templates, dialer interfaces, and ISDN BRI or PRI interfaces.

Example

The following example defines a virtual interface template that enables Multilink PPP interleaving and a maximum real-time traffic delay of 20 milliseconds, and then applies that virtual template to the Multilink PPP bundle:

interface virtual-template 1 
 ip unnumbered ethernet 0
 ppp multilink
 ppp multilink interleave
 ppp multilink fragment-delay 20 
!
multilink virtual-template 1

Related Commands

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

ip rtp reserve
ppp multilink
ppp multilink fragment-delay

ppp pap sent-username

To enable remote PAP support for an interface and use the sent-username and password elements in the PAP authentication request packet to the peer, use the ppp pap sent-username interface configuration command. Use the no form of this command to disable remote PAP support.

ppp pap sent-username username password password
no ppp pap sent-username

Syntax Description

username

Username sent in the PAP authentication request.

password

Password sent in the PAP authentication request.

password

Must contain from 1 to 25 uppercase and lowercase alphanumeric characters; cannot contain spaces or underscores.

Default

Remote PAP support disabled.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Use this command to enable remote PAP support (for example to respond to the peer's request to authenticate with PAP) and to specify the parameters to be used when sending the PAP Authentication Request.

Example

The following example configures dialer interface 0 as the dialer rotary group leader and enables PPP encapsulation on the interface. Authentication is by CHAP or PAP on received calls only. ISPCorp is the username sent to the peer if the peer requires the router to authenticate with PAP.

interface dialer0
  encapsulation ppp
  ppp authentication chap pap callin
  ppp chap hostname ISPCorp
  ppp pap sent username ISPCorp password 7 fjhfeu
  ppp pap sent-username ISPCorp password 7 1123659238

Related Commands

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

aaa authentication ppp
ppp authentication
ppp chap hostname
ppp chap password
ppp use-tacacs

ppp quality

To enable Link Quality Monitoring (LQM) on a serial interface, use the ppp quality interface configuration command. Use the no form of this command to disable LQM.

ppp quality percentage
no ppp quality

Syntax Description

percentage

Specifies the link quality threshold. Range is 1 to 100.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in a release prior to Cisco IOS Release 10.0.

The percentages are calculated for both incoming and outgoing directions. The outgoing quality is calculated by comparing the total number of packets and bytes sent to the total number of packets and bytes received by the destination node. The incoming quality is calculated by comparing the total number of packets and bytes received to the total number of packets and bytes sent by the destination node.

If the link quality percentage is not maintained, the link is deemed to be of poor quality and is taken down. LQM implements a time lag so that the link does not bounce up and down.

Example

The following example enables LQM on serial interface 2:

interface serial 2
 encapsulation ppp
 ppp quality 80

Related Commands

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

encapsulation ppp
keepalive

ppp reliable-link

To enable LAPB Numbered Mode negotiation for a reliable serial link, use the ppp reliable-link interface configuration command. To disable negotiation for a PPP reliable link on a specified interface, use the no form of the command.

ppp reliable-link
no ppp reliable-link

Syntax Description

This command has no arguments and keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.0.

Enabling LAPB Numbered Mode negotiation as a means of providing a reliable link does not guarantee that all connections through the specified interface will in fact use reliable link. It only guarantees that the router will attempt to negotiate reliable link on this interface.

PPP reliable link can be used with PPP compression over the link, but it does not require PPP compression.

PPP reliable link does not work with Multilink PPP.

You can use the show interface command to determine whether LAPB has been established on the link. You can troubleshoot PPP reliable link by using the debug lapb command and the debug ppp negotiations, debug ppp errors, and debug ppp packets commands.

Example

The following example enables PPP reliable link and predictor compression on interface BRI 0:

interface bri 0
 description Enables predictor compression on BRI 0
 ip address 170.1.1.1 255.255.255.0 
 encapsulation ppp
 dialer map ip 170.1.1.2 name starbuck 14195291357
 compress predictor
 ppp authentication chap
 dialer-group 1
 ppp reliable-link

Related Commands

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

debug lapb
debug ppp
compress
show interface

show dhcp

To display the current DHCP settings on point-to-point interfaces, use the show dhcp privileged EXEC command.

show dhcp {server | lease [interface async [number]]}

Syntax Description

server

Show known DHCP servers.

lease

Show DHCP addresses leased from a server.

interface async [number]

(Optional) Specify asynchronous interfaces and, optionally, a specific interface number.

Command Mode

Privileged EXEC

Usage Guidelines

If you omit the optional argument, the show dhcp command displays information about all interfaces.

You can use this command on any point-to-point type of interface (for example, serial, ISDN, and asynchronous) that uses DHCP for temporary IP address allocation.

Sample Display

The following is sample output from the show dhcp server command:

Router# show dhcp server
IP address pooling for Point to Point clients is: DHCP Proxy Client
DHCP Proxy Client Status:
   DHCP server: ANY (255.255.255.255)
    Leases:   0
    Offers:   0      Requests: 0     Acks: 0     Naks: 0
    Declines: 0      Releases: 0     Bad:  0

Table 111 describes the fields shown in the display.


Table 111: Show DHCP Field Descriptions
Field Description

Leases

Number of current leased IP addresses.

Offers

Number of offers for an IP address sent to a proxy-client from the server.

Requests

Number of requests for an IP address to the server.

Acks

Number of `acknowledge' messages sent by the server to the proxy-client.

Naks

Number of `not acknowledge' messages sent by the server to the proxy-client.

Declines

Number of offers from the server that are declined by the proxy-client.

Releases

Number of times IP addresses have been relinquished gracefully by the client.

Bad

Number of bad packets received from wrong length, wrong field type, etc.

Related Commands

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

ip address-pool
ip dhcp-server
peer default ip address

show ip local pool

To display statistics for any defined IP address pools, use the show ip local pool command.

show ip local pool [name]

Syntax Description

name

(Optional) Name of a specific IP address pool.

Command Mode

Privileged EXEC

Usage Guidelines

If you omit the variable name, the software will display a generic list of all defined address pools and the IP addresses that belong to them. If you specify a name, the software displays more detailed information for that pool.

Sample Display

The following is sample output from the show ip local pool command:

Router# show ip local pool
Scope    Begin           End             Free InUse
 Dialin   172.30.228.11   172.30.228.26   16   0  
Available addresses:
   172.30.228.12                             
   172.30.228.13                             
   172.30.228.14                             
   172.30.228.15                             
   172.30.228.16                             
   172.30.228.17                             
   172.30.228.18                             
   172.30.228.19                             
   172.30.228.20                             
   172.30.228.21                             
   172.30.228.22                             
   172.30.228.23                             
   172.30.228.24                             
   172.30.228.25                             
   172.30.228.26                             
   172.30.228.11        Async5               
Inuse addresses:
     None

Table 112 describes the fields shown in the display.


Table 112: Show IP Local Pool Field Descriptions
Field Description

Scope

The type of access.

Begin

The first IP address in the defined range of addresses in this pool.

End

The last IP address in the defined range of addresses in this pool.

Free

The number of addresses currently available.

InUse

The number of addresses currently in use.

Related Commands

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

ip address-pool
ip local pool

show ppp multilink

To display bundle information for the Multilink PPP bundles, use the show ppp multilink EXEC command.

show ppp multilink

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 the output when no bundles are on a system.

impulse# show ppp multilink
No active bundles

The following is sample output when a single Multilink PPP bundle (named rudder) is on a system:

systema# show ppp multilink
Bundle rudder, 3 members, first link is BRI0: B-channel 1
0 lost fragments, 8 reordered, 0 unassigned, sequence 0x1E/0x1E rcvd/sent

The following is sample output when two active bundles are on a system. Subsequent bundles would be displayed below the previous bundle.

impulse# show ppp multilink
Bundle rudder, 3 members, first link is BRI0: B-Channel 1
  0 lost fragments, 8 reordered, 0 unassigned, sequence 0x1E/0x1E rcvd/sent
Bundle dallas, 4 members, first link is BRI2: B-Channel 1
  0 lost fragments, 28 reordered, 0 unassigned, sequence 0x12E/0x12E rcvd/sent

The following example shows output when a stack group has been created. On stack group member systema on stackgroup stackq, Multilink PPP bundle hansolo has bundle interface Virtual-Access4. Two child interfaces are joined to this bundle interface. The first is a local PRI channel (serial 0:4), and the second is an interface from stack group member systemb.

systema# show ppp multilink
Bundle hansolo 2 members, Master link is Virtual-Access4
0 lost fragments, 0 reordered, 0 unassigned, 100/255 load
0 discarded,  0 lost received, sequence 40/66 rcvd/sent
members 2
 Serial0:4  
 systemb:Virtual-Access6    (1.1.1.1)

show queuing virtual-access

To display information about interleaving, use the show queuing virtual-access EXEC command.

show queuing virtual-access number

Syntax Description

number

Virtual access interface number.

Command Mode

EXEC

Sample Display

This command was first added in Cisco Release 11.3.

The folowing is sample output of the show queuing virtual-access command:

Router# show queuing virtual-access 1 
   Input queue: 0/75/0 (size/max/drops); Total output drops: 164974
   Queueing strategy: weighted fair
   Output queue: 315/64/164974/31191 (size/threshold/drops/interleaves) 
      Conversations  5/8 (active/max active)
      Reserved Conversations 2/2 (allocated/max allocated)
 
   (depth/weight/discards/interleaves) 64/4096/38669/0
   Conversation 36, linktype: ip, length: 52
   source: 140.3.3.201, destination: 225.1.2.3, id: 0x0001, ttl: 254,
   TOS: 0 prot: 17, source port 6789, destination port 2345
 
   (depth/weight/discards/interleaves) 64/4096/0/0
   Conversation 2, linktype: ip, length: 52
   source: 140.3.3.201, destination: 225.1.2.4, id: 0x0001, ttl: 254,
   TOS: 0 prot: 17, source port 5432, destination port 9870
 

Table 113 describes significant fields in the show queuing virtual-access command output.


Table 113: Show Queuing Virtual-Access Command Output
Field Description

Input queue: size, max, drops

Input queue used for virtual access interface 1, with the current size, the maximum size, and the number of dropped packets.

Total output drops

Number of output packets dropped.

Output queue: size/threshold/drops/interleaves

Output queue counters. Maximum number of packets allowed in the queue, number in the queue, the number of packets dropped due to a full queue, and the number of real-time packets interleaved among fragments of larger packets.

Conversations (active/max active)

Fair queue conversation statistics: number of conversations currently active and the maximum that have been active.

Reserved conversations (allocated, max allocated)

Reserved conversations in the weighted fair queue. (current/maxumim number allocated). Reserved conversations get the highest priority.

(depth/weight/discards/interleaves) 64/4096/38669/0

Depth of the queue, weight assigned to each packet in the queue, number of packets discarded in the queue so far, and the number of interleaves.

Conversation 36, linktype: ip, length: 52

Conversation identifier, protocol used on the link (IP), and the number of bytes.

source: 140.3.3.201, destination: 225.1.2.3,

Source IP address and destination IP address.

id: 0x0001

Protocol ID, identifying IP.

ttl: 254

Time to live, in seconds.

TOS: 0

Type of service.

prot: 17

Protocol field in IP. The value 17 indicates UDP.

source port 5432

Source TCP/UDP port.

destination port 9870

Destination TCP/UDP port.

username

To specify the password to be used in the PPP Challenge Handshake Authentication Protocol (CHAP) caller identification and Password Authentication Protocol (PAP), use the username global configuration command.

username name password secret

Syntax Description

name

Host name, server name, user ID, or command name.

password

An encrypted password for this username.

secret

For CHAP authentication: specifies the secret password for the local router or access server or the remote device. The secret is encrypted when it is stored on the local router or access server. This prevents the secret from being stolen. The secret password can consist of any string of up to 11 printable ASCII characters, but cannot include spaces or underscores. There is no limit to the number of username-password combinations that can be specified, allowing any number of remote devices to be authenticated.

Default

No password is predefined.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in a release prior to Cisco IOS Release 11.1.

Add a name entry for each remote system that the local router or access server requires authentication from.

The username command is required as part of the configuration for authentication protocols, such as CHAP and PAP. For each remote system that the local router or access server communicates with from which it requires authentication, you add a username entry.


Note To enable the local router or access server to respond to remote CHAP challenges, one username name entry must be the same as the hostname name entry that has already been assigned to your device.

If no secret is specified and debug serial-interface is enabled, an error is displayed when a link is established and the authentication protocol challenge is not implemented. Debugging information about authentication protocols is available via the debug serial-interface and debug serial-packet commands. See the Debug Command Reference publication for more information.

Example

The following example configuration enables CHAP on serial interface 0. It also defines a password for local server Adam and remote server Eve.

hostname Adam
interface serial 0
 encapsulation ppp
 ppp authentication chap
username Eve password theirsystem

When you look at your configuration file, the passwords will be encrypted and the display will look similar to the following:

hostname Adam
interface serial 0
 encapsulation ppp
 ppp authentication chap
username Eve password 7 121F0A18

Related Commands

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

hostname


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