Hello,
Wondering if somebody can help me, as I think I am missing something simple on a setup.
We have two ELAN connections going into one router (one interface is on 10.254.252.0/24 and one is 10.254.254.0/24). On each of these broadcast domains I have EBGP running back to the hub. I have 6 routers on the 10.254.252.0/24 network running EBGP and only peer direct with the Hub. Due to them being on the same subnet 10.254.252.0/24 is able to ARP for their neigh on the same subnet, the routing table looks as below for example on one of the spokes:-
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
B 1.1.1.1 [20/0] via 10.254.252.1, 00:00:12
2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2 [20/0] via 10.254.252.2, 00:00:12
3.0.0.0/32 is subnetted, 1 subnets
C 3.3.3.3 is directly connected, Loopback1
4.0.0.0/32 is subnetted, 1 subnets
B 4.4.4.4 [20/0] via 10.254.252.4, 00:00:12
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
B 10.10.10.10/32 [20/0] via 10.254.252.1, 00:00:12
C 10.254.252.0/24 is directly connected, GigabitEthernet1/0
11.0.0.0/32 is subnetted, 1 subnets
B 11.11.11.11 [20/0] via 10.254.252.1, 00:00:12
This is fine and I understand the workings (10.254.252.1 is the hub router).
On 10.254.254.0/24 I have 6 routers running EBGP again back to the same hub (mirror of the above).
The routing table on one of the spokes on this subnet is below:-
Gateway of last resort is 10.254.254.2 to network 0.0.0.0
1.0.0.0/32 is subnetted, 1 subnets
B 1.1.1.1 [20/0] via 10.254.254.2, 00:04:14
2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2 [20/0] via 10.254.254.2, 00:04:14
3.0.0.0/32 is subnetted, 1 subnets
B 3.3.3.3 [20/0] via 10.254.254.2, 00:04:14
4.0.0.0/32 is subnetted, 1 subnets
B 4.4.4.4 [20/0] via 10.254.254.2, 00:04:14
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.10.10.10/32 is directly connected, Loopback1
C 10.254.254.0/24 is directly connected, GigabitEthernet1/0
11.0.0.0/32 is subnetted, 1 subnets
B 11.11.11.11 [20/0] via 10.254.254.2, 00:04:14
B* 0.0.0.0/0 [20/0] via 10.254.254.2, 00:01:04
For some reason all routes learnt are via the hub 10.254.254.2, for routers on the 10.254.254 subnet. 11.11.11.11, should be know via 10.254.254.1 and not the hub, which is how its working on 10.254.252 network. Routes on the 10.254.252.0/24 subnet should go via the hub, but traffic on 10.254.254 should go direct.
All devices have a very basic config, nothing fancy and no filtering.
If I shutdown all networks on 10.254.252.0/24, then the routes learnt in 10.254.254 network are correct (11.11.11.11 is known via 10.254.254.1 for example).
In the real world I would filter the spokes, so they never become transit, however this would not change whats happening within the same peering subnet.
I am sure something simple is been overlooked by myself and even missing a fundamental.
This is running in live and I have run the same config in GNS3.
Please point me in the right direction, as there is something I am simply missing here.
Regards
Steven
