BGP4 Route Filters

BGP4 supports several route filters.

AS-path filter

An AS-path filter allows or denies specified prefixes from a specified autonomous system (AS). You use regular expression to match the prefixes and AS.

Community filter

A BGP community is a group of destinations that share a common property. You can filter for communities of a specified type.

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.

Prefix list

A prefix list consists of one or more conditional statements that pose an action (permit or deny) if a route matches a specified prefix.

Route map

A route map is a set of match conditions and parameter settings that the device uses to change route attributes and to control the redistribution of routes into other protocols.

Table map

A table map maps external entry attributes into the BGP routing table to preserve those attributes after they are redistributed into OSPF. For more information, see the table-map command in the Extreme SLX-OS Command Reference.