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New Member

Successive GRE Tunnels

Has anyone ever configured two successive GRE tunnels between three hops. For example: Tunnel 1 between A and B and Tunnel 2 between B and C (there are routers in between A and B and B and C). I got it to work, I can ping the routers between A and C, however, I cannot ping any packets larger than 1449 bytes nor can I send mails between two locations. This is EIGRP network.

P.S Thought this is fragmentation issue, so I tried several options including setting DF bit, Path MTU discovery (PMTUD), and IP tcp-mss adjust but the largest packet size I can ping is still 1448 bytes.

Any hint would be very appreciated. Thanks.

Don

2 REPLIES
Bronze

Re: Successive GRE Tunnels

This setup should work fine.. I would suggest that you try increasing the mtu on the tunnel interface to 1500.

http://www.cisco.com/warp/public/105/56.html

New Member

Re: Successive GRE Tunnels

GRE does not support MTU path discovery. You might want to check to see if you are blocking ICMP unreachable error messages "fragmentation needed" Type 3 Code 4

Bryan

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