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Enabling and disabling split horizon, Enabling and disabling split horizon 0 – Allied Telesis AT-8100 Series User Manual

Page 1860

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Chapter 106: Routing Information Protocol (RIP)

1860

Enabling and Disabling Split Horizon

RIP implements the split-horizon mechanism to prevent propagating
incorrect routing information and causing a loop. Split horizon blocks
routing updates from being sent out to the same gateway where the
update packet originated. This behavior optimizes communications among
multiple routing devices, particularly when links are broken. Split horizon is
enabled by default.

However, there are situations that this behavior may cause a problem and
you want to disable split horizon.

The following example disables split horizon:

awplus> enable
awplus# configure terminal
awplus(config)# interface vlan10
awplus(config-if)# no ip rip split-horizon

The following example enables split horizon:

awplus> enable
awplus# configure terminal
awplus(config)# interface vlan10
awplus(config-if)# ip rip split-horizon

The IP RIP SPLIT-HORIZON command offers an option. This command
with the POISONED keyword advertises a route with a metric of infinity or
16 if the route in a routing update is sent out to the same gateway where
the route originated.

The following example advertises a route with a metric of 16 when the
route in a routing update is sent out to the same gateway where the route
originated:

awplus> enable
awplus# configure terminal
awplus(config)# interface vlan10
awplus(config-if)# ip rip split-horizon poisoned