Table of Contents
When BGP aggregates routes, not only the aggregated route is advertised, but also the individual routes before the aggregation. Selective Aggregation allows control over which pre-aggregation routes are advertised along with the aggregate route.
This section describes BGP selective aggregation.
What is Selective Aggregation?
If the aggregate-address command is used to aggregate BGP routes, aggregate routes and all pre-aggregate routes will be advertised if no options are specified. If you configure the aggregate-address command with the summary-only option, pre-aggregate routes will not be advertised at all. In other words, it is All or Nothing for the pre-aggregation route, where the normal aggregation configuration is all sent and summary-only is not sent at all.
Selective aggregation means that instead of treating pre-aggregate routes in this All or Nothing manner, flexible control is given to the pre-aggregate routes that you wish to advertise along with the aggregate route. Selective aggregation allows only a selected portion of the pre-aggregation routes to be advertised with the aggregation route.
Selective Aggregation Methods
There are two types of selective aggregation configurations
Note that these two are very confusing. First, the range of neighbors to advertise pre-aggregation routes is different. When selective aggregation is configured with suppress-map, pre-aggregation routes are advertised to all neighbors. On the other hand, selective aggregation with unsuppress-map advertises pre-aggregated routes only to a specific neighbor.
There are also different ways to specify the pre-aggregation route you want to advertise. In both cases, a route-map is specified. However, in the case of suppress-map, the pre-aggregation routes that are denied in the route-map are advertised. In the case of unsuppress-map, the opposite is true: the pre-aggregation routes which are permitted in the route-map are advertised. This point is particularly confusing and should be noted.
|a specific neighbor
|Specify the pre-aggregation routes you want to advertise
|deny in route-map
|permit in route-map
Selective aggregation with suppress-map is explained in more detail in the following article.
Selective aggregation with unsuppress-map is explained in detail in the following article.
- Selective Aggregation allows control over which pre-aggregation routes are advertised along with the aggregation route.
- There are two methods for configuring selective aggregation
- BGP Basic Configuration and Verification Commands
- BGP Neighbor Status
- BGP Neighbor Authentication
- BGP Well Known Mandatory Attributes
- Illustration: BGP Best Path Selection
- BGP KEEPALIVE timer/Hold time Configuration
- BGP Route Minimum Advertisement Interval Configuration
- BGP Route Dampening
- BGP Route Filter Overview
- BGP Route Filter : distribute-list
- BGP Route Filter : distribute-list Configuration Example
- BGP Route Filter : prefix-list
- BGP Route Filter : prefix-list Configuration Example
- BGP Route Filter : filter-list(AS_PATH ACL)-
- BGP Route Filter : filter-list(AS_PATH ACL) Configuration Example
- BGP Route Filter : Route-map
- BGP Route Filter : route-map Configuration Example
- BGP neighbor allowas-in command
- BGP neighbor as-override command
- BGP Route RIB Failure
- BGP Route Administrative Distance Adjustment
- BGP Route Load Balancing
- BGP Auto Summary
- BGP Route Summary : network command
- BGP Route Summarization : network command configuration example
- BGP Route Summary aggregate-address command
- aggregte-address command : summary-only opiton
- aggregte-address command : attribute-map opiton
- aggregte-address command : as-set opiton
- aggregte-address command : advertise-map opiton
- BGP Selective Aggregation Overview
- BGP Selective Aggregation : suppress-map
- BGP Selective Aggregation : unsuppress-map
- BGP local-as
- BGP neighbor remove-private-AS
- bgp fast-external-fallover
- BGP Prefix Limitation