Split-Horizon with Frame-relay encap

Netstudent

This isn't a question, but rather something I found interesting. Some of you may already know this and some may not so i thought I would point it out. And maybe this post will lead to others pointing out relevant information on the topic.

Anyways using distance-vector routing protocols with Frame-relay networks could lead to problems with Split-horizon. Split-horizon can be disabled, BUT with frame-relay encap it is disabled on the physical interface by default. But it will still be enabled on subinterfaces. Anyways just something to ponder over.

mysql1988

Netstudent wrote:

This isn't a question, but rather something I found interesting. Some of you may already know this and some may not so i thought I would point it out. And maybe this post will lead to others pointing out relevant information on the topic.

Anyways using distance-vector routing protocols with Frame-relay networks could lead to problems with Split-horizon. Split-horizon can be disabled, BUT with frame-relay encap it is disabled on the physical interface by default. But it will still be enabled on subinterfaces. Anyways just something to ponder over.

assumming you are running Eigrp over a frame-relay, you might run into split horizon. When that happens you can turn of split horizon off by typing

no ip split-horizon eigrp 100

If you are running a hub and spoke environment you put this command on the hub.

Remember split horizon is, routing info sent from one interface should not be sent back to the same place it came from

dtlokee

For RIP split horizon is disabled by default on multipoint interfaces (including the physical interface) but it is not disabled for EIGRP unless you do it manually.

This is part of the reason why it is commonly accepted to use point-to-point subinterfaces. They eliminate the need for disabling split horizion but can increase the overall size of your routing table if you're not careful in the design.

Obliged

A Frame Relay multipoint interface, even in a hub and spoke Frame Relay topology can run into "Split Horizon" issues. If everythig else works and one router is prevented from learning about another router on the same network. It's very likely that they cant see each other because of Split Horizon.
Am I making any sense?