Hello We had similar problems and we used 1524 bytes mtu's in serials interfaces in the cisco config: # int ser 0 # mtu 1524 I am also interested in extra info regarding this gre problem, but for a quick fix try playing with mtu size over serials interfaces. Kind regards Josema At 09:53 AM 6/5/98 +0100, philip bridge wrote:
I'm experiencing problems with fragmentation due to Cisco GRE tunnel overhead: the way I understand it, the MTU if a GRE tunnel will always be less than the MTU of the underlying IP cloud (in our case 1500 bytes) due to the IP encapsulation overhead. So 1500 byte packets attempting to traverse the tunnel will be fragmented, or dropped if the DF bit is set, in which case an ICMP message is send back to the originating host