FTOS Configuration Guide for the C-Series - Force10 Networks

Filtering with Regular ExpressionFigure 356 applies access list Eagle to routes inbound from BGP peer
10.5.5.2. Access list Eagle uses a regular expression to deny routes originating in AS 32.
Figure 356 Filtering with Regular Expression
Force10(config)#router bgp 99
Force10(conf-router_bgp)#neigh AAA peer-group
Force10(conf-router_bgp)#neigh AAA no shut
Force10(conf-router_bgp)#show conf
!
router bgp 99
neighbor AAA peer-group
neighbor AAA no shutdown
neighbor 10.155.15.2 remote-as 32
neighbor 10.155.15.2 shutdown
Force10(conf-router_bgp)#neigh 10.155.15.2 filter-list 1 in
Force10(conf-router_bgp)#ex
Force10(conf)#ip as-path access-list Eagle
Force10(config-as-path)#deny 32$
Force10(config-as-path)#ex
Force10(conf)#router bgp 99
Force10(conf-router_bgp)#neighbor AAA filter-list Eagle in
Force10(conf-router_bgp)#show conf
!
router bgp 99
neighbor AAA peer-group
neighbor AAA filter-list Eaglein
neighbor AAA no shutdown
neighbor 10.155.15.2 remote-as 32
neighbor 10.155.15.2 filter-list 1 in
neighbor 10.155.15.2 shutdown
Force10(conf-router_bgp)#ex
Force10(conf)#ex
Force10#show ip as-path-access-lists
ip as-path access-list Eagle
deny 32$
Force10#
Table 50 lists the Regular Expressions accepted in FTOS.
Table 50 Regular Expressions
Regular
Expression Definition
^ (carrot) Matches the beginning of the input string.
Alternatively, when used as the first character within brackets [^ ] matches any number
except the ones specified within the brackets.
$ (dollar) Matches the end of the input string.
. (period) Matches any single character, including white space.
Create the Access List and Filter
Regular Expression shown
as part of Access List filter
* (asterisk) Matches 0 or more sequences of the immediately previous character or pattern.
494 Border Gateway Protocol (BGP)