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Foundry Configuration Guide for the FESX, FSX, and FWSX
C - 14
© Foundry Networks, Inc.
December 2005
BGP4 Community Filters
BGP4 community filters control whether the Foundry device learns or drops BGP4 route information based on the
route’s community membership.
Actions
•
A BGP4 community filter applied to inbound packets permits (learns) or denies (drops) routes for networks
with the specified community membership in BGP4 updates received from a BGP4 neighbor.
•
A BGP4 AS-path filter applied to outbound packets permits (advertises) or denies (drops) routes for networks
with the specified community membership in BGP4 updates sent to a BGP4 neighbor.
Scope
You define BGP4 community filters globally, then apply them as part of a BGP4 neighbor's distribute list or as part
of a match statement in a route map.
Syntax
Use the following CLI commands to configure BGP4 community filters.
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 14-49.
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 14-49.
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 14-1 for more
information.
Figure B.10 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. The default redistribution action is
permit, even after you configure a redistribution filter. To maintain tight control over redistribution, define a “deny
any” redistribution filter as the last filter (the one with the highest ID) and deny permit filters for specific routes.
Table C.15: BGP4 Community Filters
CLI syntax
FESX424 Router(config-bgp-router)# community-filter <filter-num>
permit | deny <num> | internet | no-advertise | no-export
FESX424 Router(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>]
Summary of Contents for FastIron Edge Switch X424
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