Command:

ip split-horizon (IGRP)


Mode:

Router(config-if)#


Syntax:

ip split-horizon.

no ip split-horizon

 

Syntax Description:

This command has no arguments or keywords.

Command Description:

 

To enable the split horizon mechanism, use the ip split-horizon command in interface configuration mode. To disable the split horizon mechanism, use the no form of this command.

 

For all interfaces except those for which either Frame Relay or Switched Multimegabit Data Service (SMDS) encapsulation is enabled, the default condition for this command is ip split-horizon; in other words, the split horizon feature is active. If the interface configuration includes either the encapsulation frame-relay or encapsulation smds command, then the default is for split horizon to be disabled. Split horizon is not disabled by default for interfaces using any of the X.25 encapsulations.

Note: For networks that include links over X.25 packet-switched networks (PSNs), the neighbor router configuration command can be used to defeat the split horizon feature. You can as an alternative explicitly specify the no ip split-horizon command in your configuration. However, if you do so you must similarly disable split horizon for all routers in any relevant multicast groups on that network.

Note: If split horizon has been disabled on an interface and you want to enable it, use the ip split-horizon command to restore the split horizon mechanism.

Note: In general, changing the state of the default for the ip split-horizon command is not recommended, unless you are certain that your application requires a change in order to advertise routes properly. If split horizon is disabled on a serial interface (and that interface is attached to a PSN), you must disable split horizon for all routers and access servers in any relevant multicast groups on that network.


Example:

The following simple example disables split horizon on a serial link. The serial link is connected to an X.25 network.

interface serial 0

encapsulation x25

no ip split-horizon


Misconceptions:

           None.


Related Commands:

network (IGRP)


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