Configuring BGP4
December 2005 © Foundry Networks, Inc. 21 - 55
Deleting a Community from a BGP4 Route
To delete a community from a BGP4 route’s community attributes field, enter commands such as the following:
FESX424 Router(config)# ip community-list standard std_3 permit 12:99 12:86
FESX424 Router(config)# route-map bgp6 permit 1
FESX424 Router(config-routemap bgp6)# match ip address 1
FESX424 Router(config-routemap bgp6)# set comm-list std_3 delete
The first command configures a community ACL containing community numbers 12:99 and 12:86. The remaining
commands configure a route map that matches on routes whose destination network is specified in ACL 1, and
deletes communities 12:99 and 12:86 from those routes. The route does not need to contain all the specified
communities in order for them to be deleted. For example, if a route contains communities 12:86, 33:44, and
66:77, community 12:86 is deleted.
Syntax: set comm-list <acl> delete
The <acl> parameter specifies the name of a community list ACL.
Using a Table Map To Set the Tag Value
Route maps that contain set statements change values in routes when the routes are accepted by the route map.
For inbound route maps (route maps that filter routes received from neighbors), this means that the routes are
changed before they enter the BGP4 route table.
For tag values, if you do not want the value to change until a route enters the IP route table, you can use a table
map to change the value. A table map is a route map that you have associated with the IP routing table. The
Layer 3 Switch applies the set statements for tag values in the table map to routes before adding them to the route
table.
To configure a table map, you configure the route map, then identify it as a table map. The table map does not
require separate configuration. You create it simply by calling an existing route map a table map. You can have
one table map.
NOTE: Use table maps only for setting the tag value. Do not use table maps to set other attributes. To set other
route attributes, use route maps or filters.
To create a route map and identify it as a table map, enter commands such as following. These commands create
a route map that uses an address filter. For routes that match the address filter, the route map changes the tag
value to 100. This route map is then identified as a table map. As a result, the route map is applied only to routes
that the Layer 3 Switch places in the IP route table. The route map is not applied to all routes. This example
assumes that address filter 11 has already been configured.
FESX424 Router(config)# route-map TAG_IP permit 1
FESX424 Router(config-routemap TAG_IP)# match address-filters 11
FESX424 Router(config-routemap TAG_IP)# set tag 100
FESX424 Router(config-routemap TAG_IP)# router bgp
FESX424 Router(config-bgp-router)# table-map TAG_IP
Configuring Cooperative BGP4 Route Filtering
By default, the Layer 3 Switch performs all filtering of incoming routes locally, on the Layer 3 Switch itself. You can
use cooperative BGP4 route filtering to cause the filtering to be performed by a neighbor before it sends the routes
to the Layer 3 Switch. Cooperative filtering conserves resources by eliminating unnecessary route updates and
filter processing. For example, the Layer 3 Switch can send a deny filter to its neighbor, which the neighbor uses
to filter out updates before sending them to the Layer 3 Switch. The neighbor saves the resources it would
otherwise use to generate the route updates, and the Layer 3 Switch saves the resources it would use to filter out
the routes.
When you enable cooperative filtering, the Layer 3 Switch advertises this capability in its Open message to the
neighbor when initiating the neighbor session. The Open message also indicates whether the Layer 3 Switch is
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