Overview

The unsuppress-map allows you to determine which pre-aggregation routes to advertise along with the aggregation routes for each neighbor.

Selective Aggregation with unsuppress-map

unsuppress-map is prefixed with “un” which cancels out “suppress”, so it means “not suppress”. The idea of unsuppress-map is to first suppress all pre-aggregation routes with summary-only option. The operation is then to specify a “per neighbor” ” unsuppressed” pre-aggregation routes and advertise to that neighbor along with the aggregate route.

Figure: Selective Aggregation with unsuppress-map

Let’s consider the configuration of the unsuppress-map. First, specify summary-only as an option for aggregate-address. This will suppress all pre-aggregation routes for now. Then, specify unsuppress-map for a particular neighbor as follows

unsuppress-map Configuration

(config)#router bgp <AS>
(config-router)#aggregate-address <network-address> <subnetmask> summary-only
(config-router)#neighbor <ip-address> unsuppress-map <route-map-name>

<AS>:AS number
<network-address>: Network address of the aggregate route
<subnetmask>: Subnet mask of the aggregate route
<route-map-name>: route-map name

After unsuppress-map, specify the route-map. The pre-aggregation routes that have been permit in the route-map are released from transmission suppression and advertised together with the aggregate route.

unsuppres-map configuration example

For R1 in “Figure: Selective Aggregation with unsupress-map,” the configuration is as follows

R1 unsupress-map configuration example

access-list 2 permit 192.168.0.0
access-list 2 permit 192.168.2.0
!
access-list 3 permit 192.168.1.0
access-list 3 permit 192.168.3.0
!
route-map UNSUPP-R2 permit 10
 match ip address 2
!
route-map UNSUPP-R3 permit 10
 match ip address 3
!
router bgp 
 aggregate-address 192.168.0.0 255.255.252.0 summary-only
 neighbor R2 unsuppress-map UNSUPP-R2
 neighbor R3 unsuppress-map UNSUPP-R3

Figure: unsupress-map configuration example
Figure: unsupress-map configuration example

And note the BGP table when unsuppress-map is configured. In the unsuppress-map configuration, the summary-only option of the aggregate-address command is specified, so all the entries for the pre-aggregate route are “s(suppressed)”.

Example of BGP table with unsuppress-map configured

R1#sh ip bgp 
BGP table version is 8, local router ID is 100.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.0.0/22   0.0.0.0                            32768 i
s> 192.168.0.0/24   0.0.0.0                  0         32768 i
s> 192.168.1.0/24   0.0.0.0                  0         32768 i
s> 192.168.2.0/24   0.0.0.0                  0         32768 i
s> 192.168.3.0/24   0.0.0.0                  0         32768 i

All the routes in the BGP table are marked with an “s”, but if you look at show ip bgp neighbor advertised-routes, you can see the pre-aggregation routes advertised.

Summary

Points

  • Selective aggregation is performed for each neighbor by unsupress-map.
  • Specify a route-map after the neighbor unsuppress-map command. The routes that are permit in the route-map are advertised along with the aggregate route.

How the BGP works