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Basic BGP:How to make this aggregate-address work?

Imagine my goal is to advertise a summarized prefix 10.177.206.0/23 which represents 10.177.206.0/24 and 10.177.207.0/24 networks.

Then I wrote the below. However, the ISP still sees 10.177.207.0/24 and 10.177.206.0/24 instead of only one summarized entry 10.177.206.0/23 as I

wish.

Given that I do not have a more specific routing in the bgp table for networks 10.177.206.0 and 10.177.207.0, that means the aggregate-address is not working for me, if I understand this correctly.


Question:
Is there any way to make this aggregate command work in my case or do I need to rely on individual network statements advertising 10.177.206.0/24 and 10.177.207.0/24?

R2#show run | b bgp

router bgp 100

no synchronization

bgp log-neighbor-changes

network 10.177.206.0 mask 255.255.255.0

network 10.177.207.0 mask 255.255.255.0

aggregate-address 10.177.206.0 255.255.255.254 summary-only

R2#show ip bgp

BGP table version is 6, local router ID is 10.2.255.32

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

*> 4.4.4.4/32       10.2.47.193              0             0 200 i

R2#

R2#show ip route | i 10.177.20

O       10.2.95.1/32 [110/2] via 10.177.206.1, 00:19:09, FastEthernet2/0

O       10.2.80.0/24 [110/2] via 10.177.206.1, 00:19:09, FastEthernet2/0

O       10.177.220.0/24 [110/2] via 10.177.206.1, 00:19:09, FastEthernet2/0

O       10.177.207.0/24 [110/2] via 10.177.206.1, 00:19:09, FastEthernet2/0

C       10.177.206.0/24 is directly connected, FastEthernet2/0

O       10.2.255.47/32 [110/3] via 10.177.206.1, 00:19:09, FastEthernet2/0

O       192.168.1.1 [110/2] via 10.177.206.1, 00:19:09, FastEthernet2/0

ISP is seeing:

Gateway of last resort is not set

     4.0.0.0/32 is subnetted, 1 subnets

C       4.4.4.4 is directly connected, Loopback0

     10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks

C       10.2.55.0/24 is directly connected, FastEthernet0/0

B       10.177.207.0/24 [20/2] via 10.2.47.204, 00:01:04

B       10.177.206.0/24 [20/0] via 10.2.47.204, 00:01:04

C       10.2.47.192/28 is directly connected, FastEthernet1/0

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: Basic BGP:How to make this aggregate-address work?

Marlon

You have the wrong mask ie.

aggregate-address 10.177.206.0 255.255.255.254 summary-only

should be

aggregate-address 10.177.206.0 255.255.254.0 summary-only

Also do you have either 10.177.206.0/24 or 10.177.207.0/24 in your routing table without the network statements ?

If not you only need to have one network statement under BGP for one of the networks.

Jon

2 REPLIES
Hall of Fame Super Blue

Re: Basic BGP:How to make this aggregate-address work?

Marlon

You have the wrong mask ie.

aggregate-address 10.177.206.0 255.255.255.254 summary-only

should be

aggregate-address 10.177.206.0 255.255.254.0 summary-only

Also do you have either 10.177.206.0/24 or 10.177.207.0/24 in your routing table without the network statements ?

If not you only need to have one network statement under BGP for one of the networks.

Jon

Community Member

Re: Basic BGP:How to make this aggregate-address work?

10.177.206.0/24 seems to be a connected route on an interface.

10.177.207.0/24 is learned via OSPF.

Does the OP still need to have a network statement, or can he just aggregate both into a summary, since they're already in the RIB?

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