Tuesday, November 11, 2008

BGP Unsuppress Maps

Within BGP routes can be summarized using the 'aggregate-address' command. When the summary-only option is utilised all granular routes within the summary range are suppressed.

If a BGP neighbor requires some of the granular routes within the summary this can be achieved via use of the 'unsuppress-map' neighbor command.

Of note here!!! When defining the routes to be unsuppressed do NOT use an acl - this simply does not work in my experience. Use a prefix-list and all works as expected.

router bgp 100
aggregate-address summary-only
neighbor unsuppress-map R3

route-map R3
match ip address prefix-list R3

ip prefix-list R3 seq 10 permit
ip prefix-list R3 seq 15 permit
ip prefix-list R3 seq 20 permit
ip prefix-list R3 seq 25 permit

An alternative to using the 'summary-only' key word on the aggregate-address command is via the 'suppress-map' option can be used to achieve the same net result.
route-map SUPPRESS
router bgp 100
aggregate-address suppress-map SUPPRESS

In summary routes can be suppressed on the aggregate-address command and unsupressed in a more garnular fashion with the neighbor commands.

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