Filter
Top Products
KEY WORD IN COMMAND DEFINABLE FILTER WAY TO APPLY FILTERING
ACL access-list Ye s
Distribute list distribute-list Ye s
Prefix list prefix-list Ye s
Ye s
AS path list as-path Ye s
Filter list filter-list Ye s
Route map route-map Ye s Ye s
Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes | Page 7
BGP: Overview of the Available Filter Types
Difference and Relationship in BGP
Examples for filtering BGP Update messages
All above filters can be used in incoming or outgoing directions of the update messages. For
ACL, distribute list, AS path list, and prefix list, the order of application is not important. If an
update is denied by any given filter, it is discarded immediately, and is not run through any of
the other filters. If an update is permitted by one filter, it is passed through to the next filter
to be considered. At the end, you end up with the set of updates that all the filters agree
should not be discarded. However, route maps are applied last, after the other types of filter.
This is because route maps can modify updates, not just accept or discard them.
DEFINABLE
FILTER
WAY TO APPLY FILTERING
DISTRIBUTE LIST PREFIX LIST FILTER LIST ROUTE MAP
ACL YES YES
Prefix list YES YES
AS path list YES YES
Route map YES