GRE Tunnel Problem with same tunnel source

[renemerki1]

Hi 

I have one Main location and 2 destination. I want to have 2 GRE tunnels one to each destination.

The Problem is, that one tunnel in the Main location does not come up. (up/down).

I've a Cisco CAT6500 at the Main location with 12.2(33)SXI4a.

When I create the new Tunnel i got following error:

%Warning: Using same source IP for more than one IP/GRE tunnels
%may cause %software switching packets for tunnels using
%this address. If possible, use a %unique tunnel source for
%Interface Tunnel20
noveukues03s(config-if)#end

The Tunnel 20 (red) will not come up. Any Idee how to solve this issue ?

I need the same tunnel source "vlan10"

MAIN:

interface Tunnel10
 ip address 192.168.10.1 255.255.255.252
 ip mtu 1476
 ip tcp adjust-mss 1430
 keepalive 1 3
 tunnel source Vlan10
 tunnel destination 10.163.82.129

!

interface Tunnel20
 ip address 192.168.20.1 255.255.255.252
 ip mtu 1476
 ip tcp adjust-mss 1430
 keepalive 1 3
 tunnel source Vlan10
 tunnel destination 10.162.64.6
end

Destination A

interface Tunnel10
 ip address 192.168.10.2 255.255.255.252
 no ip redirects
 ip mtu 1476
 ip tcp adjust-mss 1430
 load-interval 30
 keepalive 1 3
 tunnel source Vlan118
 tunnel destination 10.166.8.10

Destination B

interface Tunnel20
 ip address 192.168.20.2 255.255.255.252
 no ip redirects
 ip mtu 1476
 ip tcp adjust-mss 1430
 keepalive 1 3
 tunnel source Vlan64
 tunnel destination 10.166.8.10

thanks

René

[Richard Burts]

Rene

The message that you get is informational and warns that there may be a performance impact if you configure two GRE tunnels which use the same source address. I do not believe that this has anything to do with the result that the second tunnel is up/down. I suspect that the up/down result is because the keepalives are failing between your 6500 and the device at destination B. As a test of that theory you could remove the keepalives configured for tunnel 20. If you do that I suspect that the tunnel will become up/up.

But up/up does not necessarily mean that the tunnel is working or will pass two way traffic. As the next step I would ask that you attempt from the 6500 to ping 10.162.64.6 sourcing the ping from vlan 10. And from destination B try to ping 10.166.8.10 sourcing the ping from vlan 64.

Try these and let us know the results.

HTH

Rick

[renemerki1]

Hi Richard,

Yes this was the problem. Removing keepalives helps.

I've also moved the GRE to a "Router" behind the Cat 6500. but same effect. one Site GRE "up/down".

I've already tested extended pings between the "tunnels" before that works all the time.

Now all works fine. (no keepalives)

Many thanks

René

[Richard Burts]

Rene

Moving the GRE from the 6500 to a router will certainly address the potential performance issue. I am glad that my suggestion about removing keepalive was helpful.

HTH

Rick