Concept Guide

Aggregating Routes
When BGP peers exchange information about the networks, a large BGP routing tables is created. Dell EMC Networking OS provides
multiple ways to aggregate routes to reduced the size of the BGP routing table which helps to improve the network performance by
reducing the convergence time. You can congure BGP to congure and advertise aggregated routes. At least one specic route of the
aggregate must be in the routing table for the congured aggregate to become active.
To aggregate routes, use the following command.
AS_SET includes AS_PATH and community information from the routes included in the aggregated route.
• Assign the IP address and mask of the prex to be aggregated.
CONFIG-ROUTER-BGP mode
aggregate-address ip-address mask [advertise-map map-name] [as-set] [attribute-map map-name]
[summary-only] [suppress-map map-name]
– as-set- Specify that the advertised path of this route is an AS_SET.
– summary-only-Create aggregate route and suppress advertisements of specic routes to all neighbors.
– suppress-map map-name-Create aggregate route by suppressing the advertisements of specic routes.
– advertise-map map-name-Create aggregate route by advertising specic routes.
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 Routes Using Route Maps
To lter routes using a route map, use these commands.
1 Create a route map and assign it a name.
CONFIGURATION mode
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Border Gateway Protocol (BGP)