Brocade TurboIron 24X Series Configuration Guide - Manual (Page 738)

704 Brocade TurboIron 24X Series Configuration Guide
53-1003053-01
Filtering
NOTE
The Layer 3 Switch cannot actively support AS-path filters and AS-path 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 updates that do not match a filter is “deny”. To
change the default action to “permit”, configure the last filter or ACL as “permit any any”.
AS-path filters or AS-path ACLs can be referred to by a BGP neighbor's filter list number as well as
by match statements in a route map.
Defining an AS-path filter
To define AS-path filter 4 to permit AS 2500, enter the following command.
TurboIron(config-bgp-router)#as-path-filter 4 permit 2500
Syntax: as-path-filter permit | deny
The parameter identifies the filter position in the AS-path filter list and can be from 1 – 100.
Thus, the AS-path filter list can contain up to 100 filters. The Layer 3 Switch applies the filters in
numerical order, beginning with the lowest-numbered filter. When a filter match is true, the Layer 3
Switch stops and does not continue applying filters from the list.
NOTE
If the filter is referred to by a route map match statement, the filter is applied in the order in which
the filter is listed in the match statement.
The permit | deny parameter indicates the action the router takes if the filter match is true.
• If you specify permit, the router permits the route into the BGP4 table if the filter match is true.
• If you specify deny, the router denies the route from entering the BGP4 table if the filter match
is true.
The parameter indicates the AS-path information. You can enter an exact AS-path string
if you want to filter for a specific value. You also can use regular expressions in the filter string.
Defining an AS-path ACL
To configure an AS-path list that uses ACL 1, enter a command such as the following.
TurboIron(config)#ip as-path access-list 1 permit 100
TurboIron(config)#router bgp
TurboIron(config-bgp-router)#neighbor 10.10.10.1 filter-list 1 in
The ip as-path command configures an AS-path ACL that permits routes containing AS number 100
in their AS paths. The neighbor command then applies the AS-path ACL to advertisements and
updates received from neighbor 10.10.10.1. In this example, the only routes the Layer 3 Switch
permits from neighbor 10.10.10.1 are those whose AS-paths contain AS-path number 100.
Syntax: ip as-path access-list [seq ] deny | permit
The parameter specifies the ACL name. (If you enter a number, the CLI interprets the
number as a text string.)