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CONFIGURATION mode
ip as-path access-list as-path-name
2. Create a AS-PATH ACL filter with a deny or permit action.
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 configured route map.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} filter-list as-path-name {in | out}
Configure 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 configured 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 configured, 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 .* filter in your AS-PATH ACL.
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 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 filtering
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:
● 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).
NOTE:
When you configure 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 filter routes using prefix lists, use the following commands.
1. Create a prefix list and assign it a name.
CONFIGURATION mode
ip prefix-list prefix-name
2. Create multiple prefix list filters with a deny or permit action.
CONFIG-PREFIX LIST mode
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Border Gateway Protocol IPv4 (BGPv4)