Computer networks that use different protocols on a variety of local-area network (LAN) media over a variety of wide-area network (WAN) technologies must be able to communicate with other networks. Additionally, dial-in users must be able to access the same network services that local users can access. The Cisco Internetwork Operating System (Cisco IOS) software provides these capabilities. The Cisco IOS software runs on internetworking products purchased directly from Cisco Systems, Inc. and from many Cisco partners.
This chapter describes the capabilities of the Cisco IOS software implemented on router and access server platforms. It contains the following sections:
We provide various documents about your Cisco access server or router.
The Cisco IOS software supports users and applications throughout the enterprise and provides security and data integrity for the internetwork. The Cisco IOS software manages resources cost effectively by controlling and unifying complex, distributed network information. It also functions as a flexible vehicle for adding new services, features, and applications to the internetwork.
The Cisco IOS software provides several internetwork benefits, which are described in the following sections:
Scalability provides the flexibility required to address all of the key issues facing internetworks as organizations evolve. The Cisco IOS software utilizes scalable routing protocols to avoid needless congestion, overcome inherent protocol limitations, and bypass many of the obstacles that result from the complex scope and geographical dispersion of an internetwork.
The Cisco IOS software reduces network costs by efficiently using network bandwidth and resources while eliminating the need for static routes. Advanced Cisco IOS features such as route filtering, protocol termination and translation, smart broadcasts, and helper address services combine to create a flexible, scalable infrastructure that can keep pace with evolving network requirements.
The Cisco IOS software is reliable and adaptive because it identifies the best network paths and routes traffic around network failures.
Policy-based Cisco IOS features such as route filtering and route redistribution save network resources by preventing data from being unnecessarily broadcast to nodes that do not need it. Priority output queuing and custom queuing grant priority to important sessions when network bandwidth is scarce. Load balancing uses every available path across the internetwork to preserve valuable bandwidth and improve network performance. The Cisco IOS software also provides the most effective and efficient scaling available for network applications that require transparent or source-route bridging algorithms.
Increasingly, internetworks are incorporating new technologies such as Asynchronous Transfer Mode (ATM) and LAN switching. With CiscoFusion, Cisco's scalable architecture for switched internetworks, the Cisco IOS software provides the framework for a new technology called multilayer switching, which fuses the ease of switching solutions with the power of routed solutions.
By distributing routing intelligence and switching functions to create "virtual LANs," the CiscoFusion multilayer switching capabilities increase bandwidth while simplifying moves, additions, and changes across the enterprise. CiscoFusion extends the power and flexibility of the Cisco IOS software beyond internetwork routers to include the ATM and LAN switches that are increasingly being deployed throughout today's internetworks.
Depending on the product you purchased, your Cisco device connects terminals, modems, microcomputers, and networks over serial lines to local-area networks (LANs) or wide-area networks (WANs). Cisco products provide network access to terminals, printers, workstations, and other networks.
On LANs, terminal services support TCP/IP on UNIX machines with Telnet and rlogin connections, IBM machines with TN3270 connections, and Digital machines with LAT connections. You can use the router or access server's protocol translation services to make connections between hosts and resources running different protocols including router and access server connections to X.25 machines using X.25 PAD.
Access servers provide remote configuration through Telnet and Digital Equipment Corporation's Maintenance Operation Protocol (MOP) connections to virtual ports.
The Cisco IOS software supports four types of server operation:
Figure 2 illustrates these types of server functionality available on access servers: remote node service is demonstrated by the remote PC connection running SLIP, CSLIP, PPP, or XRemote; terminal service is shown between the terminals and hosts running the same protocol (LAT-to-LAT or TCP-to-TCP); protocol translation is shown between the terminals and hosts running unlike protocols (LAT-to-TCP or TCP-to-LAT); asynchronous IP routing is shown by the PC running SLIP or PPP, and between the two access servers.
Because most network costs are expended on WAN switching and bandwidth requirements, a cost-effective internetwork must optimize all WAN-related operations. Optimization increases network throughput while reducing delay time. It also reduces costs by eliminating unnecessary traffic and selecting the most economical WAN links available.
The Cisco IOS software seamlessly accommodates circuit-switched WAN services such as Integrated Services Digital Network (ISDN), switched T1, and dial-up telephone lines. Cisco IOS software innovations such as dial-on-demand access and dial backup capabilities provide cost-effective alternatives to point-to-point switched leased lines. Support for advanced, packet-switched services such as X.25, Frame Relay, Switched Multimegabit Data Service (SMDS), and ATM extends the internetwork across the broad range of WAN interface alternatives now available.
In addition to remote node WAN connectivity with ARA, SLIP, PPP, or XRemote, other WAN services include dial-on-demand routing (DDR) of IP and IPX, X.25, Frame Relay, and SMDS.
The Cisco IOS software provides an array of network management and security capabilities designed to meet the needs of today's large, complex internetworks. Integrated management simplifies administrative procedures and shortens the time required to diagnose and fix problems. Automated operations reduce hands-on tasks and make it possible to manage large, geographically dispersed internetworks with a small staff of experts located at a central site.
The Cisco IOS software provides several important management features that are built into every Cisco router and access server. These management features include configuration services, which lower the cost of installing, upgrading, and reconfiguring routers and access servers, as well as comprehensive monitoring and diagnostic services. In addition, the Cisco IOS software provides valuable information and services for router management applications developed by Cisco and its partners. The Cisco applications, known collectively as CiscoWorks, offer administrators a wide-ranging suite of operational, design, and management capabilities that increase productivity and reduce costs.
The Cisco IOS management services are matched by their security capabilities. The Cisco IOS software includes a diverse tool kit for partitioning resources and prohibiting access to sensitive or confidential information and processes. Multidimensional filters prevent users from knowing that other users or resources are even on the network. Encrypted passwords, dial-in authentication, multilevel configuration permissions, network data encryption, and accounting and logging features provide protection from--and information about--unauthorized access attempts and data eavesdropping attempts.
The following sections describe the two software tools that you can use to configure your access server or router via the Cisco IOS software:
The Cisco Configuration Builder allows you to create configuration files for multiple routers or access servers without knowing the command-line language or syntax. It is a Microsoft Windows-based application that runs on an IBM PC or compatible computer.
To use Configuration Builder, refer to the Cisco Configuration Builder Getting Started Guide.
If you do not have the platform required to run Configuration Builder, configure your Cisco device using the command interpreter, as described in the next section.
You can build most straightforward configurations and create a configuration file using the setup command facility. This facility is described in the "Using ClickStart, AutoInstall, and Setup" chapter.
The Cisco IOS software provides a user interface called a command interpreter, or EXEC, that allows you to configure and manage the router or access server. The user interface also provides context-sensitive help. The command interpreter has several command modes, each of which provides a group of related commands that you can use to configure the routing device and display its status. Some commands are available to all users; others can be executed only after the user enters an enabling password. Context-sensitive help gives information about command syntax. The command interpreter and its help feature are described in the "Understanding the User Interface" chapter.
You use the command interpreter (also known as the command-line parser) to configure interfaces, terminal sessions, and asynchronous communications lines. Interfaces are connections to network media, such as Ethernet, Token Ring, and serial media. You configure them to run routing and networking protocols. You configure terminal sessions and modems connected to the router or access server so that other network users can log in to the network over asynchronous lines. Configuring terminal sessions and asynchronous communications lines is discussed in the "Configuring Terminal Lines and Modem Support" chapter of the Access Services Configuration Guide. Configuring interfaces is described in the "Configuring Interfaces" chapter of this manual. The routing, bridging, and IBM protocols you can configure on these interfaces are described in their protocol-specific configuration guides.
You also can configure and manage the router or access server itself, performing such tasks as naming the device, setting the time, configuring SNMP, and setting security. These tasks are described in the "Managing the System" chapter.
The basic process to set up your access server or router follows:
Step 1 Attach an RS-232 ASCII terminal to the system console port located at the rear of the
Step 2 Configure the terminal to operate at 9600 baud, 8 data bits, no parity, 2 stop bits.
Step 3 Power up the router. The setup command facility runs automatically for initial startup.
Step 4 Perform general system configuration.
Step 5 Configure your system for by referring to the appropriate part in the documentation.
To enhance the configuration, perform the protocol-specific tasks described in the appropriate chapters of the Cisco IOS software configuration guides.
You can issue most of the Cisco IOS commands using a Web browser. This Cisco IOS feature is accessed by using the Cisco Web browser interface. You access the Cisco Web browser interface through the router's home page. All Cisco routers and access servers loaded with the latest version of Cisco IOS software have a home page, which is password protected.
From the router's home page, click on a hypertext link titled "Monitor the Router." This link takes you to a Web page that has a "Command" field. You can type commands in this field as if you were using the command interpreter on a terminal connected to the router. The page also displays a list of commands. You can execute these commands by clicking on them, as if you were clicking on hypertext links. This feature is documented in the "Understanding the User Interface" chapter.
ClickStart is a Cisco IOS software feature that allows you to configure a router using a Web browser. Like the Cisco Web browser interface, you access ClickStart from the router's home page. To use ClickStart, enter information about your internet service in a form called "EZ Setup." ClickStart builds a configuration for your router based on the information you provide in the "EZ Setup" form. You do not need to have an extensive background in networks and routers to configure your router using ClickStart.
ClickStart can be used to configure a router to connect a small office or home PC to the Internet or to another network. In this environment, your PC is connected to the router via an Ethernet connection. You configure the router to dial your Internet service provider, and your Internet service provider supplies an ISDN, Frame Relay, or Asynchronous Serial connection to the Internet.
You can use ClickStart to configure a Cisco 1003 or Cisco 1004 ISDN router running Cisco IOS Release 11.0(6) or later software, or Cisco IOS Release 11.1(2) or later software. You can also use ClickStart to configure a Cisco 1005 Frame Relay or Asynchronous Serial router running Cisco IOS Release 11.1(5) or later software. This feature is documented in the "Using ClickStart, AutoInstall, and Setup" chapter.
Our routers and access servers support the following industry-standard networking media:
These media are described briefly in the "Configuring Interfaces" chapter.
The Cisco IOS software supports many networking protocols, as well as their associated routing protocols. These protocols are based on both open standards and proprietary protocols from a variety of vendors. The Cisco IOS software also supports a wide set of bridging and IBM connectivity solutions.
The Cisco IOS software can receive and forward packets concurrently from any combination of the following:
The "Configuring IP Routing Protocols" chapter in the Network Protocols Configuration Guide, Part 1 describes these protocols in detail.
The "Configuring AppleTalk" chapter in the Network Protocols Configuration Guide, Part 2 describes these protocols in detail.
The Cisco IOS software supports the following Novell IPX routing protocols:
The "Configuring Novell IPX" chapter in the Network Protocols Configuration Guide, Part 2 describes these protocols in detail.
Routing protocols for Apollo Domain, Banyan VINES, DECnet, ISO CLNS, and XNS are described in the Network Protocols Configuration Guide, Part 3.