Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 632)

When next-hop recursion is enabled, if the first lookup for the destination IP address results in an
IBGP path that originated in the same AS, the device performs lookup for the IP address of the next-
hop gateway. This goes on until the final lookup results in an IGP route. Otherwise, the route is
declared unreachable.
Route filtering
The following route filters are supported:
• AS-path filter
• Community filter
• Prefix list
• Route map
• Table map
NOTE
Support for access lists in route filtering is not available, and has been replaced by prefix-list filtering.
BGP does not use community and extended-community filters directly. Rather, it uses them indirectly
through route-map filtering by means of the route-map command.
Timers
You can change keepalive and hold-time values from their default values of 60 and 180 seconds,
respectively:
sw0(config-bgp-router)# timers keep-alive 10 hold-time 60
A hold-time value of 0 means that the device will wait indefinitely for messages from a neighbor
without tearing down the session.
Once the IGP routes are changed, BGP routing tables are affected after 5 seconds by default. You
can change this value by using the update-time command:
sw0(config-bgp-ipv4u)# update-time 0
An update-time value of 0 will trigger BGP route calculation immediately after the IGP routes are
changed.
Using route maps
A route map is a named set of match conditions and parameter settings that the device can use to
modify route attributes and to control redistribution of the routes into other protocols. A route map
consists of a sequence of instances, the equivalent of rows in a table. The device evaluates a route
according to route map instances in ascending numerical order. The route is first compared against
instance 1, then against instance 2, and so on. When a match is found, the device stops evaluating
the route.
Route maps can contain match clauses and set statements. Each route map contains a permit or
deny statement for routes that match the match clauses:
• If the route map contains a permit statement, a route that matches a match statement is permitted;
otherwise, the route is denied.
• If the route map contains a deny statement, a route that matches a match statement is denied.
Route filtering
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