Controlling the Number of Prefixes

As the routing table increases in size, the processor and memory resources required to process routing information increases. Some peers send so much routing information that a BGP speaker can be overwhelmed by the updates. You can use the neighbor maximum-prefix command to limit how many prefixes can be received from a neighbor.

The router resets the BGP connection when the specified maximum is exceeded. You can use the warning-only keyword to log a warning rather than reset the connection. You can also configure the router so that a warning is logged when a specified percentage of the maximum is exceeded.

In the following example, the router is configured to reset the BGP connection when it receives more than 1,000 prefixes from its neighbor at 2.2.2.2:

neighbor maximum-prefix

• Use to control how many prefixes can be received from a neighbor.
• If you specify a BGP peer group by using the peerGroupName argument, all the members of the peer group inherit the characteristic configured with this command unless it is overridden for a specific peer.
• By default, BGP checks the maximum prefix limit only against accepted routes. You can specify the strict keyword to force BGP to check the maximum prefix against all received routes. The accepted and received routes will likely differ when you have configured inbound soft reconfiguration and route filters for incoming traffic.
• This command takes effect immediately. To prevent a peer from continually flapping, when it goes to state idle because the maximum number of prefixes has been reached, the peer stays in state idle until you use the clear ip bgp command to issue a hard clear.
• Use the no version to remove the maximum number of prefixes.
• See neighbor maximum-prefix

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