Cisco Systems 78-11741-02 manual Configuration for Router a, Configuration for Router B, IPC-211

Configuring Routing Information Protocol

RIP Configuration Task List

Figure 35 Disabled Split Horizon Example for Frame Relay Network

Network address:			Network address:
	10.20.40.0			20.155.120.0
		Interface address:			Interface address:
		10.20.40.1			20.155.120.1
	E0			E2
		S0		Router B S2
	Router C

Network address:

12.13.50.0

				Secondary
	Interface address:					Interface address:
	12.13.50.1	Interface address:		interface address:
						131.108.1.2
			128.125.1.1	131.108.1.1
E1					Network
	S1		Network		address:
					131.108.1.0
Router A		Interface address:	address:
			128.125.1.0
		128.125.1.2
					Frame Relay
					network	S1069a

In this example, split horizon is disabled on all serial interfaces. However, split horizon must be disabled on Router C in order for network 128.125.0.0 to be advertised into network 131.108.0.0, and vice versa. These subnets overlap at Router C, interface S0. If split horizon were enabled on serial interface S0, it would not advertise a route back into the Frame Relay network for either of these networks.

Configuration for Router A

interface ethernet 1 ip address 12.13.50.1

!

interface serial 1

ip address 128.125.1.2 encapsulation frame-relay no ip split-horizon

Configuration for Router B

interface ethernet 2

ip address 20.155.120.1

!

interface serial 2

ip address 131.108.1.2 encapsulation frame-relay no ip split-horizon

Configuration for Router C

interface ethernet 0 ip address 10.20.40.1

!

interface serial 0

ip address 128.125.1.1

ip address 131.108.1.1 secondary encapsulation frame-relay

no ip split-horizon

Cisco IOS IP Configuration Guide

IPC-211