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Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 35 Configuring IP Unicast Routing
Configuring RIP
To disable IP summarization, use the
no ip summary-address rip
router configuration command.
In this example, the major net is 10.0.0.0. The summary address 10.2.0.0 overrides the autosummary
address of 10.0.0.0 so that 10.2.0.0 is advertised out interface Gigabit Ethernet port 2, and 10.0.0.0 is
not advertised. In the example, if the interface is still in Layer 2 mode (the default), you must enter a
no
switchport
interface configuration command before entering the
ip address
interface configuration
command.
Note
If split horizon is enabled, neither autosummary nor interface summary addresses (those configured with
the
ip summary-address rip
router configuration command) are advertised.
Switch(config)#
router rip
Switch(config-router)#
interface gi1/0/2
Switch(config-if)#
ip address 10.1.5.1 255.255.255.0
Switch(config-if)#
ip summary-address rip 10.2.0.0 255.255.0.0
Switch(config-if)#
no ip split-horizon
Switch(config-if)#
exit
Switch(config)#
router rip
Switch(config-router)#
network 10.0.0.0
Switch(config-router)#
neighbor 2.2.2.2 peer-group mygroup
Switch(config-router)#
end
Configuring 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 can optimize communication among multiple routers, especially when links are
broken.
Note
In general, we do not recommend disabling split horizon unless you are certain that your application
requires it to properly advertise routes.
Beginning in privileged EXEC mode, follow these steps to disable split horizon on the interface:
To enable the split horizon mechanism, use the
ip split-horizon
interface configuration command.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface
interface-id
Enter interface configuration mode, and specify the interface to
configure.
Step 3
ip address
ip-address subnet-mask
Configure the IP address and IP subnet.
Step 4
no ip split-horizon
Disable split horizon on the interface.
Step 5
end
Return to privileged EXEC mode.
Step 6
show ip interface
interface-id
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
