R2(config-router)#aggregate-address 184.108.40.206 255.255.255.0 ? advertise-map Set condition to advertise attribute
as-set Generate AS set path information
attribute-map Set attributes of aggregate nlri Nlri aggregate applies to route-map Set parameters of aggregate summary-only Filter more specific routes from updates suppress-map Conditionally filter more specific routes from updates <cr>
You could presumably use summary-only to filter all the more specific routes, however what if you wanted to suppress only a selected few of the more specific routes and advertise the rest of the specific routes along with the aggregate? This is where "suppress-map" or "advertise-map" comes to the rescue If you only had a few specific routes to advertise but a lot of specific routes to suppress out of an aggregate then you would use the "advertise-map" to advertise just what you want. However, if you only had a few specific routes to suppress but more specific prefixes to advertise then you would use a "suppress-map" to suppress what you want and advertise the rest. See below for "suppress-map" in action.
- Suppress 220.127.116.11/25 from being advertised to R3 but 18.104.22.168/25 and the aggregate should be advertised to R3.
hostname R2 ! ip prefix-list suppress-pre seq 10 permit 22.214.171.124/25 ! route-map rm-suppress-map permit 10 match ip address prefix-list suppress-pre ! router bgp 2 aggregate-address 126.96.36.199 255.255.255.0 suppress-map rm-suppress-map
- Permit what needs to be denied by specifying it the prefix-list.
- Create a route-map to match the prefix-list.
- Attach the route-map to the suppress-map parameter.
R2#show ip bgp BGP table version is 5, local router ID is 188.8.131.52 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 *> 184.108.40.206/25 220.127.116.11 0 0 1 i *> 18.104.22.168/24 0.0.0.0 32768 i s> 22.214.171.124/25 126.96.36.199 0 0 1 i
Notice the "s" flag which means that route is suppressed and as you can see that route is not being advertised to R3.
R2#show ip bgp nei 188.8.131.52 advertised-routes
Total number of prefixes 0 R2#show ip bgp nei 184.108.40.206 advertised-routes BGP table version is 5, local router ID is 220.127.116.11 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 *> 18.104.22.168/25 22.214.171.124 0 0 1 i *> 126.96.36.199/24 0.0.0.0 32768 i
Have you used this before? Where would you use this feature?
Many more articles to come so stay tuned.
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