This scenario involves use of the suppress-map with BGP aggregate-address command. It is fairly simple to understand but I could use the practice.
R1 is getting the following routes from R2 in AS 200:
R1#show ip bgp | Begin Network
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 172.12.12.22 0 0 200 i
r> 2.2.2.3/32 172.12.12.22 0 0 200 i
*> 200.1.1.2/32 172.12.12.22 0 0 200 i
*> 200.2.2.2/32 172.12.12.22 0 0 200 i
*> 200.3.3.2/32 172.12.12.22 0 0 200 i
On R2 we can configure aggregation with the following command:
R2(config-router)#aggregate-address 200.0.0.0 255.0.0.0
Without clearing BGP, here is R1's BGP table with the aggregate 200.0.0.0/8:
R1#show ip bgp | Begin Network
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 172.12.12.22 0 0 200 i
r> 2.2.2.3/32 172.12.12.22 0 0 200 i
*> 200.0.0.0/8 172.12.12.22 0 0 200 i
*> 200.1.1.2/32 172.12.12.22 0 0 200 i
*> 200.2.2.2/32 172.12.12.22 0 0 200 i
*> 200.3.3.2/32 172.12.12.22 0 0 200 i
Suppose we wanted to suppress only some of the "component routes", but not all. With the summary-only keyword we would suppress all, but with a suppress-map we can supress a few.
on R2 we add the following:
access-list 50 permit 200.1.1.2
access-list 50 permit 200.3.3.2
!
route-map BLOCK permit 10
match ip address 50
!
router bgp 200
aggregate-address 200.0.0.0 255.0.0.0 suppress-map BLOCK
!
Note that the access-list "permits" the networks and the supress-map matches whatever networks are permitted by the ACL and suppresses them.
Now on R1 we have:
R1#show ip bgp | Begin Network
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 172.12.12.22 0 0 200 i
r> 2.2.2.3/32 172.12.12.22 0 0 200 i
*> 200.0.0.0/8 172.12.12.22 0 0 200 i
*> 200.2.2.2/32 172.12.12.22 0 0 200 i
R1 is getting the following routes from R2 in AS 200:
R1#show ip bgp | Begin Network
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 172.12.12.22 0 0 200 i
r> 2.2.2.3/32 172.12.12.22 0 0 200 i
*> 200.1.1.2/32 172.12.12.22 0 0 200 i
*> 200.2.2.2/32 172.12.12.22 0 0 200 i
*> 200.3.3.2/32 172.12.12.22 0 0 200 i
On R2 we can configure aggregation with the following command:
R2(config-router)#aggregate-address 200.0.0.0 255.0.0.0
Without clearing BGP, here is R1's BGP table with the aggregate 200.0.0.0/8:
R1#show ip bgp | Begin Network
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 172.12.12.22 0 0 200 i
r> 2.2.2.3/32 172.12.12.22 0 0 200 i
*> 200.0.0.0/8 172.12.12.22 0 0 200 i
*> 200.1.1.2/32 172.12.12.22 0 0 200 i
*> 200.2.2.2/32 172.12.12.22 0 0 200 i
*> 200.3.3.2/32 172.12.12.22 0 0 200 i
Suppose we wanted to suppress only some of the "component routes", but not all. With the summary-only keyword we would suppress all, but with a suppress-map we can supress a few.
on R2 we add the following:
access-list 50 permit 200.1.1.2
access-list 50 permit 200.3.3.2
!
route-map BLOCK permit 10
match ip address 50
!
router bgp 200
aggregate-address 200.0.0.0 255.0.0.0 suppress-map BLOCK
!
Note that the access-list "permits" the networks and the supress-map matches whatever networks are permitted by the ACL and suppresses them.
Now on R1 we have:
R1#show ip bgp | Begin Network
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 172.12.12.22 0 0 200 i
r> 2.2.2.3/32 172.12.12.22 0 0 200 i
*> 200.0.0.0/8 172.12.12.22 0 0 200 i
*> 200.2.2.2/32 172.12.12.22 0 0 200 i
