Users Guide

AS-PATH ACL mode
{deny | permit} as-regular-expression
3. Return to CONFIGURATION mode.
AS-PATH ACL
exit
4. Enter ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
5. Filter routes based on the criteria in the congured route map.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} filter-list as-path-name {in | out}
Congure the following parameters:
• ip-address or peer-group-name: enter the neighbor’s IP address or the peer group’s name.
• as-path-name: enter the name of a congured AS-PATH ACL.
• in: apply the AS-PATH ACL map to inbound routes.
• out: apply the AS-PATH ACL to outbound routes.
To view which commands are congured, use the show config command in CONFIGURATION ROUTER BGP mode and the
show ip as-path-access-list command in EXEC Privilege mode.
To forward all routes not meeting the AS-PATH ACL criteria, include the permit .* lter in your AS-PATH ACL.
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 Networking OS supports up to 255 characters in a set community statement inside a route map.
NOTE: With Dell Networking OS, 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 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 that the changes are made, always reset the neighbor or
peer group by using the clear ip bgp command in EXEC Privilege mode.
To lter routes using prex lists, use the following commands.
1. Create a prex list and assign it a name.
CONFIGURATION mode
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Border Gateway Protocol IPv4 (BGPv4)