Concept Guide

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 prex 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. Prex lists lter routes based on route and prex length, while AS-Path ACLs lter routes
based on the ASN. Route maps can lter 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 ltering 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:
• prex 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 ltering BGP routes, create the prex list, AS-PATH ACL, or route map.
For conguration information about prex lists, AS-PATH ACLs, and route maps, refer to Access Control Lists (ACLs).
NOTE
: When you congure a new set of BGP policies, to ensure the changes are made, always reset the neighbor or peer group
by using the clear ip bgp command in EXEC Privilege mode.
Filtering BGP using IP prex lists
An IP prex lists contains a list of networks. When applying an IP prex list to a BGP neighbor, you can able to send or receive the routes
whose destination is in the IP prex list.
Filtering BGP routes based on IP prex lists involves the following steps:
• Create a prex list. The steps 1 to 3 in the following conguration commands shows how to create a prex list.
• Applying the created prex list to a BGP neighbor. The steps 4 and 5 show how the prex list is applied to a neighbor.
To congure an IP prex list, use the following commands.
1 Create a prex list and assign it a name.
CONFIGURATION mode
220
Border Gateway Protocol (BGP)