Brocade TurboIron 24X Series Configuration Guide - Manual (Page 741)

Brocade TurboIron 24X Series Configuration Guide 707
53-1003053-01
Filtering
If you want to filter for a special character instead of using the special character, enter “\”
(backslash) in front of the character. For example, to filter on AS-path strings containing an
asterisk, enter the asterisk portion of the regular expression as “\*”.
TurboIron(config-bgp-router)#as-path-filter 2 deny \*
To use the backslash as a string character, enter two slashes. For example, to filter on AS-path
strings containing a backslash, enter the backslash portion of the regular expression as “\\”.
TurboIron(config-bgp-router)#as-path-filter 2 deny \\
Filtering communities
You can filter routes received from BGP4 neighbors based on community names. Use either of the
following methods to do so.
A community is an optional attribute that identifies the route as a member of a user-defined class
of routes. Community names are arbitrary values made of two five-digit integers joined by a colon.
You determine what the name means when you create the community name as one of a route
attributes. Each string in the community name can be a number from 0 – 65535.
This format allows you to easily classify community names. For example, a common convention
used in community naming is to configure the first string as the local AS and the second string as
the unique community within that AS. Using this convention, communities 1:10, 1:20, and 1:30
can be easily identified as member communities of AS 1.
The Layer 3 Switch provides the following methods for filtering on community information:
• Community filters
• Community list ACLs
NOTE
The Layer 3 Switch cannot actively support community filters and community list ACLs at the same
time. Use one method or the other but do not mix methods.
NOTE
Once you define a filter or ACL, the default action for communities that do not match a filter or ACL
is “deny”. To change the default action to “permit”, configure the last filter or ACL entry as “permit
any any”.
Community filters or ACLs can be referred to by match statements in a route map.
Defining a community filter
To define filter 3 to permit routes that have the NO_ADVERTISE community, enter the following
command.
TurboIron(config-bgp-router)#community-filter 3 permit no-advertise
Syntax: community-filter permit | deny : | internet | local-as | no-advertise
| no-export
The parameter identifies the filter position in the community filter list and can be from 1 –
100. Thus, the community filter list can contain up to 100 filters. The router applies the filters in
numerical order, beginning with the lowest-numbered filter. When a filter match is true, the router
stops and does not continue applying filters from the list.