Concept Guide

Regular
Expression
Denition
| (pipe) Matches characters on either side of the metacharacter; logical OR.
As seen in the following example, the expressions are displayed when using the show commands. To view the AS-PATH ACL conguration,
use the show config command in CONFIGURATION AS-PATH ACL mode and the show ip as-path-access-list command in
EXEC Privilege mode.
For more information about this command and route ltering, refer to Filtering BGP Routes.
The following example 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. The rst lines shown in bold create the access list and lter. The second lines shown in bold are the regular
expression shown as part of the access list lter.
Example of Using Regular Expression to Filter AS Paths
DellEMC(config)#router bgp 99
DellEMC(conf-router_bgp)#neigh AAA peer-group
DellEMC(conf-router_bgp)#neigh AAA no shut
DellEMC(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
DellEMC(conf-router_bgp)#neigh 10.155.15.2 filter-list 1 in
DellEMC(conf-router_bgp)#ex
DellEMC(conf)#ip as-path access-list Eagle
DellEMC(config-as-path)#deny 32$
DellEMC(config-as-path)#ex
DellEMC(conf)#router bgp 99
DellEMC(conf-router_bgp)#neighbor AAA filter-list Eagle in
DellEMC(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
DellEMC(conf-router_bgp)#ex
DellEMC(conf)#ex
DellEMC#show ip as-path-access-lists
ip as-path access-list Eagle
deny 32$
DellEMC#
Redistributing Routes
In addition to ltering routes, you can add routes from other routing instances or protocols to the BGP process. You can congure the
device to redistribute ISIS, OSPF, static, or directly connected routes into BGP process using the redistribute command.
To add routes from other routing instances or protocols, use any of the following commands in ROUTER BGP mode.
• Include directly connected or user-congured (static) routes into BGP.
ROUTER BGP or CONF-ROUTER_BGPv6_ AF mode
redistribute {connected | static} [route-map map-name]
224
Border Gateway Protocol (BGP)