These replicated
broadcast packets consume bandwidth and cause signi?¬?cant latency variations in
user traf?¬?c.
The following methods exist to solve the routing update reachability issue:
?– To solve the reachability issues brought on by split horizon, turn off split horizon.
However, two problems exist with this solution. First, although most network layer
protocols, such as IP, do allow you to disable split horizon, not all network layer
protocols allow you to do this. Second, disabling split horizon increases the chances of
routing loops in your network.
?– Use a fully meshed topology; however, this topology increases the cost.
?– Use subinterfaces. To enable the forwarding of broadcast routing updates in a hub-andspoke
Frame Relay topology, you can con?¬?gure the hub router with logically assigned
interfaces called subinterfaces, which are logical subdivisions of a physical interface.
In split horizon routing environments, routing updates that are received on one
subinterface can be sent out another subinterface. In subinterface con?¬?guration, each
VC can be con?¬?gured as a point-to-point connection, which allows each subinterface
to act like a leased line.
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