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Summary addresses and split horizon – Cisco 15327 User Manual

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11-8

Ethernet Card Software Feature and Configuration Guide, R7.2

Chapter 11 Configuring Networking Protocols

Configuring RIP

Beginning in privileged EXEC mode, follow this procedure to configure RIP authentication on an
interface:

To restore clear text authentication, use the no ip rip authentication mode interface configuration
command. To prevent authentication, use the no ip rip authentication key-chain interface
configuration command.

Summary Addresses and Split Horizon

Routers connected to broadcast-type IP networks and using distance-vector routing protocols normally
use the split-horizon mechanism to reduce the possibility of routing loops. Split horizon blocks
information about routes from being advertised by a router on any interface from which that information
originated. This feature usually optimizes communication among multiple routers, especially when links
are broken.

Note

In general, disabling split horizon is not recommended unless you are certain that your application
requires it to properly advertise routes.

If you want to configure an interface running RIP to advertise a summarized local IP address pool on a
network access server for dial-up clients, use the ip summary-address rip interface configuration
command.

Beginning in privileged EXEC mode, follow these steps to set an interface to advertise a summarized
local IP address pool and to disable split horizon on the interface:

Command

Purpose

Step 1

Router# configure terminal

Enters global configuration mode.

Step 2

Router(config)# interface

interface-id

Enters interface configuration mode, and specifies the
interface to configure.

Step 3

Router(config-if)# ip rip

authentication key-chain

name-of-chain

Enables RIP authentication.

Step 4

Router(config-if)# ip rip

authentication mode

{text | md5}

Configures the interface to use plain text
authentication (the default) or MD5 digest
authentication.

Step 5

Router(config-if)# end

Returns to privileged EXEC mode.

Step 6

Router# show running-config interface

[

interface-id]

Verifies your entries.

Step 7

Router# copy running-config

startup-config

(Optional) Saves your entries in the configuration file.

Command

Purpose

Step 1

Router# configure terminal

Enters global configuration mode.

Step 2

Router(config)# interface

interface-id

Enters interface configuration mode, and specifies the
Layer 3 interface to configure.

Step 3

Router(config-if)# ip address

ip-address subnet-mask

Configures the IP address and IP subnet.