Cisco Systems 78-11741-02 Split Horizon Examples, Example 2 Incorrect Configuration, IPC-210

Configuring Routing Information Protocol

RIP Configuration Task List

Example 2: Incorrect Configuration

The following example shows an illegal use of the ip summary-address rip router configuration command, because both addresses to be summarized have the same major network. Each route summarization on an interface must have a unique major network, whether or not the addresses have unique address masks.

Router(config)# interface ethernet1

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Router(config-if)# ip summary-address rip 10.1.0.0 255.255.0.0 Rotuer(config-if)# ip summary-address rip 10.2.0.0 255.255.255.0

Split Horizon Examples

Two examples of configuring split horizon are provided.

Example 1

The following configuration shows a simple example of disabling split horizon on a serial link. In this example, the serial link is connected to an X.25 network.

interface serial 0 encapsulation x25 no ip split-horizon

Example 2

In the next example, Figure 35 illustrates a typical situation in which the no ip split-horizoninterface configuration command would be useful. This figure depicts two IP subnets that are both accessible via a serial interface on Router C (connected to Frame Relay network). In this example, the serial interface on Router C accommodates one of the subnets via the assignment of a secondary IP address.

The Ethernet interfaces for Router A, Router B, and Router C (connected to IP networks 12.13.50.0, 10.20.40.0, and 20.155.120.0, respectively, all have split horizon enabled by default, while the serial interfaces connected to networks 128.125.1.0 and 131.108.1.0 all have split horizon disabled with the no ip split-horizoncommand. Figure 35 shows the topology and interfaces.

Cisco IOS IP Configuration Guide

IPC-210