BGP Aggregate AS-SET

Hello Stefanita,

The aggregate-address command can summarize anything that is in the BGP table. The summary-only option defines whether you advertise the summary route next to the regular route or only the summary route. Quick example:

R4#show run int l4
Building configuration...

Current configuration : 69 bytes
!
interface Loopback4
 ip address 123.123.123.123 255.255.255.0
end
R4#show run | section bgp
router bgp 4
 bgp log-neighbor-changes
 network 123.123.123.0 mask 255.255.255.0
 neighbor 192.168.14.1 remote-as 1

123.123.123.0/24 shows up on R1 like this:

R1#show ip bgp | include 123
 *>   123.123.123.0/24 192.168.14.4             0             0 4 i

And R1 forwards it to R2 and R3. Here’s R2:

R2#show ip bgp | include 123
 *>   123.123.123.0/24 192.168.12.1                           0 1 4 i

Let’s summarize it:

R1(config)#router bgp 1
R1(config-router)#aggregate-address 123.123.0.0 255.255.0.0

Now it shows up on R2 (and R3) like this:

R2#show ip bgp | include 123
 *>   123.123.0.0/16   192.168.12.1             0             0 1 i
 *>   123.123.123.0/24 192.168.12.1                           0 1 4 i

Let’s try the summary-only command:

R1(config)#router bgp 1
R1(config-router)#aggregate-address 123.123.0.0 255.255.0.0 summary-only 

And it shows up like this:

R2#show ip bgp | include 123
 *>   123.123.0.0/16   192.168.12.1             0             0 1 i

Does this help?

I updated the picture btw to add the network addresses and IP addresses :slight_smile:

Rene

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