Install Guide

As seen in the following example, the expressions are displayed when using the show commands. To view the AS-PATH
ACL configuration, 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 filtering, 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 first lines shown in bold create the access list and filter. The second lines
shown in bold are the regular expression shown as part of the access list filter.
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#
Filtering BGP Routes
Filtering routes allows you to implement BGP policies.
You can use either IP prefix lists, route maps, AS-PATH ACLs or IP community lists (using a route map) to control which routes
the BGP neighbor or peer group accepts and advertises. Prefix lists filter routes based on route and prefix length, while AS-Path
ACLs filter routes based on the ASN. Route maps can filter and set conditions, change attributes, and assign update policies.
NOTE: Dell EMC Networking OS supports up to 255 characters in a set community statement inside a route map.
NOTE: You can create inbound and outbound policies. Each of the commands used for filtering has in and out parameters
that you must apply. In Dell EMC Networking OS, the order of preference varies depending on whether the attributes are
applied for inbound updates or outbound updates.
For inbound and outbound updates the order of preference is:
● prefix lists (using the neighbor distribute-list command)
● AS-PATH ACLs (using the neighbor filter-list command)
● route maps (using the neighbor route-map command)
Prior to filtering BGP routes, create the prefix list, AS-PATH ACL, or route map.
For configuration information about prefix lists, AS-PATH ACLs, and route maps, refer to Access Control Lists (ACLs).
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Border Gateway Protocol (BGP)