Cisco 900 Series ISR Software Configuration Guide

Basic Router Configuration

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This chapter provides configuration procedures for Cisco 900 series integrated services routers (ISRs). It also includes configuration examples and verification steps whenever possible. This chapter contains the following topics:

Basic Configuration

• Default Configuration
• Configuring Global Parameters

Interface Configuration

• Interface Ports
• Configuring Gigabit Ethernet Interfaces
• Configuring a Loopback Interface

Routing Configuration

• Configuring Command-Line Access
• Configuring Static Routes
• Configuring Dynamic Routes

Default Configuration

When you boot up your Cisco router for the first time, you notice some basic configuration has already been performed. Use the show running-config command to view the initial configuration, as shown in the following example.

Configuring Global Parameters

This example shows how to configure router global parameters. By configuring global parameters, you specify a name for the router, an encrypted password to prevent unauthorized access to the router, and disables the router from translating unfamiliar words (typos) into IP addresses.

For complete information on global parameter commands, see the Cisco IOS Release configuration guide documentation set.

Configuring I/O Memory Allocation

To reallocate the percentage of DRAM in use for I/O memory and processor memory on Cisco 900 series ISR routers, use the memory-size iomem i/o-memory-percentage command in global configuration mode. To revert to the default memory allocation, use the no form of this command. This procedure enables smartinit.

When you specify the percentage of I/O memory in the command line, the processor memory automatically acquires the remaining percentage of DRAM memory.

This example shows how to allocate 25% of the DRAM memory to I/O memory and the remaining 75% to processor memory:

Verifying IOMEM Setting

Interface Ports

Table 3-1 lists the interfaces that are supported on Cisco 900 series integrated services routers.

Configuring Gigabit Ethernet Interfaces

This example shows how to configure the onboard Gigabit Ethernet (GE) interfaces:

Note Switch ports support Auto, Full, and Half Duplex. WAN ports support only Full Duplex.

Use show interface command to verify the interface configuration. The following example shows the output for the switch port:

The following example shows the output for the WAN port:

Configuring a Loopback Interface

The loopback interface acts as a placeholder for the static IP address and provides default routing information.

This example shows how loopback interface is used to support Network Address Translation (NAT) on the virtual-template interface. This configuration example shows the loopback interface configured on the gigabit ethernet interface with an IP address of 200.200.100.1/24, which acts as a static IP address. The loopback interface points back to virtual-template1, which has a negotiated IP address.

To verify that you have properly configured the loopback interface, enter the show interface loopback command. You should see verification output similar to the following example.

Another way to verify the loopback interface is to ping it:

Configuring Command-Line Access

The TTY lines are asynchronous lines used for inbound or outbound modem and terminal connections and can be seen in a router or access server configuration as line x. The specific line numbers are a function of the hardware built into or installed on the router or access server. In Cisco 900 series routers, the TTY lines are incremented by 1 and start with line number3.

This example shows the command-line access commands. You do not need to input the commands marked “default.” These commands appear automatically in the configuration file generated when you use the show running-config command.

Configuring Static Routes

Static routes provide fixed routing paths through the network. They are manually configured on the router. If the network topology changes, the static route must be updated with a new route. Static routes are private routes unless they are redistributed by a routing protocol.

In this configuration example, the static route sends out all IP packets with a destination IP address of 192.168.1.0 and a subnet mask of 255.255.255.0 on the Gigabit Ethernet interface to another device with an IP address of 10.10.10.2. Specifically, the packets are sent to the configured PVC.

You do not need to enter the command marked “(default).” This command appears automatically in the configuration file generated when you use the show running-config command.

To verify that you have properly configured static routing, enter the show ip route command and look for static routes signified by the “S.”

You should see verification output similar to the following:

Configuring Dynamic Routes

In dynamic routing, the network protocol adjusts the path automatically, based on network traffic or topology. Changes in dynamic routes are shared with other routers in the network.

The Cisco routers can use IP routing protocols, such as Routing Information Protocol (RIP) or Enhanced Interior Gateway Routing Protocol (EIGRP), to learn routes dynamically. You can configure either of these routing protocols on your router.

• Configuring Routing Information Protocol
• Configuring Enhanced Interior Gateway Routing Protocol