R2(config-router)#aggregate-address 11.11.11.0 255.255.255.0 ? 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.
Objective:
- Suppress 11.11.11.128/25 from being advertised to R3 but 11.11.11.0/25 and the aggregate should be advertised to R3.
hostname R2
!
ip prefix-list suppress-pre seq 10 permit 11.11.11.128/25
!
route-map rm-suppress-map permit 10
match ip address prefix-list suppress-pre
!
router bgp 2
aggregate-address 11.11.11.0 255.255.255.0 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 2.2.2.2
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
*> 11.11.11.0/25 1.1.1.1 0 0 1 i
*> 11.11.11.0/24 0.0.0.0 32768 i
s> 11.11.11.128/25 1.1.1.1 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 2.2.2.3 advertised-routes
Total number of prefixes 0
R2#show ip bgp nei 2.2.2.3 advertised-routes
BGP table version is 5, local router ID is 2.2.2.2
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
*> 11.11.11.0/25 1.1.1.1 0 0 1 i
*> 11.11.11.0/24 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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