Tunnel question GRE/OSPF

DevilWAH

OK so I have 3 routers (just mucking around so not real world)

A

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B

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C

1. A and C have loopback of 1.1.1.1 and 2.2.2.2
2. all three routes have point to point links A <> B and B<> C
3. A and B have interface F0/0 up linking to B
4. A(.1) <> B(.2) is the sub net 192.168.1.0 /24 and B(.2) <> C(.1) is subnet 192.168.2.0/24
5 all active physical and loop back interfaces on all three routers are in area 0
6. OSPF SPF has run and all routers can see all networks via OSPF and the command ping 1.1.1.1 source 2.2.2.2 from C works

7. on router A the commands

#int tunnel 0
#ip address 10.10.10.1 255.255.255.0
#tunnel source int f0/0
#tunnel destination 192.168.2.1
#ip ospf 1 area 0

8. on router C the commands

#int tunnel 0
#ip address 10.10.10.2 255.255.255.0
#tunnel source int f0/0
#tunnel destination 192.168.1.1
#ip ospf 1 area 0

9. the tunnel comes up, I can ping both of the 10.0.0.x addresses and a trace route shows they go via the tunnel (single hop), and they should in the routing table as via the tunnel

10. a new neighbor relation ship is formed between A and C via the tunnel interface.

However the 1.1.1.1 and 2.2.2.2 address are still seen via router C address, from either A or C. But I want traffic going from A to C to use the tunnel. Or more that when I have BGP running on A <> C as iBGP there are no routing loops and the internal ospf protocol does not need to know about it.

What simple thing am i missing?

Cheers

elderkai

Well, compare the cost of those routes going through B vs. over the tunnel. Manipulate the costs to how you want them to be.

wintermute000

networking-forum.com - View topic - OSPF Cost through a GRE Tunnel

DevilWAH

Doh, thank you

Although cost is not going to do it here. Or at least not simple interface costs, do that can it ends up the end points of the tunnel are best cost to go through the tunnel and then of course the tunnel Drops

O        112.168.1.1/30 [110/2] via 192.168.10.1, 00:00:11, Tunnel0   
                         [110/2] via 192.168.20.1, 00:13:54, GigabitEthernet1/0

Easy to resolve but I suppose this is what the high tunnel cost is for, to prevent loops. Or don't use a tunnel to pass traffic from the same routing protocol that you are learning the tunnel endpoint networks routes from.

wintermute000

or PBR
or Statics
or VRFs (which is a different way of doing what you said)

If you use BGP and establish adjacencies across the tunnel there is no issue.