Split Horizon

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Split horizon is a technique used to avoid routing loops . With split horizon, the router does not advertise a route over the interface in which the route is learned from. For example, in Figure 4-1, Router 1 receives an update about Network X from Router 2 over the serial interface. If split horizon is enabled, Router 2 will not advertise the Network X route back to Router 1 over the same serial interface. If split horizon is disabled, Router 2 will advertise Network X back to Router 1. When Network X becomes unavailable in Router 2, Router 2 believes that Router 1 still has a valid route to Network X and sends the packet destined to Network X toward Router 1, which will be dropped.

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Troubleshooting IP Routing Protocols
Troubleshooting IP Routing Protocols (CCIE Professional Development Series)
ISBN: 1587050196
EAN: 2147483647
Year: 2002
Pages: 260

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