Foundry Networks Switch and Router Installation And Configuration Manual page 1040

Foundry Switch and Router Installation and Configuration Guide
Syntax
Use the following CLI commands or Web management interface panels to configure BGP4 community filters.
CLI syntax
BigIron(config-bgp-router)# community-filter <filter-num> permit | deny
<num> | internet | no-advertise | no-export
BigIron(config-bgp-routemap RMAP_NAME)# match
as-path-filters | community-filters | address-filters <num,num,...>
[metric <num>] [next-hop <ip-addr>]
[route-type internal | external-type1 | external-type2]
[tag <tag-value>]
NOTE: The match command compares the information you configure for the command's parameters against
BGP routes. You use this command when configuring a route map. If the comparison matches a route, set
statements in the route map specify the action to take. See "Defining Route Maps" on page 19-63.
Redistribution Filters
Redistribution filters control the exchange of routes between routing protocols. RIP, OSPF, and BGP4 support
redistribution of one another's routes. In addition, they all allow exchange of static routes.
You configure RIP and OSPF redistribution filters to permit or deny routes for specific network addresses.
Optionally, you can also filter on and modify the route metric. To configure redistribution, you configure
redistribution filters in the protocol that will receive the routes. Redistribution is disabled by default in RIP and
OSPF and enabled by default in BGP4.
BGP4 redistribution filters can filter based on a route's metric, weight, and also on the results of comparison of the
route information with a route map. A route map is a named set of match conditions and parameter settings that
a Foundry Layer 3 Switch can use to modify route attributes and to control redistribution of routes. For more
information, see "Defining Route Maps" on page 19-63.
BGP4 allows you to include the redistribution filters as part of a route map. A route map examines and modifies
route information exchanged between BGP4 and RIP or OSPF. See "Configuring BGP4" on page 19-1 for more
information.
Figure C.8 shows an example of a redistribution filter. In this example, redistribution filters in OSPF are configured
to redistribute two RIP routes into OSPF. Notice that unlike some other filter examples in this appendix, a filter for
permitting all routes (to change the default action) is not configured. To maintain tight control over redistribution,
the default action "deny any" is allowed to remain. Only routes that explicitly match the permit filters are permitted
to be redistributed. Thus, in Figure C.8, the RIP route to 191.47.12.0/24 is not redistributed because there is no
"permit any" filter that changes the default action from deny to permit.
C - 36
Table C.24: BGP4 Community Filters
Web management links
Configure->BGP->Community Filter
Configure->BGP->Route Map Filter
December 2000