Ip6gre and fragmentation

if I need to pass MPLS packets via gre, then no problem. But I have to set the “nopmtudisc” option. In this case, I can set any MTU on the tunnel interface. A GRE packets will be fragmented, and the fragments will be reassembled at the remote end of the tunnel. Everything is fine.

But I can’t do the same with ip6gre. The nopmtudisc option is not applicable. As a result, the router sets a lower MTU on the tunnel interface and the MPLS packets are dropped. Is it possible to solve this problem with ip6gre ?

I think this problems is not originate or solved by “nopmtudisc” which is related to path-mtu , However, it might be resolved by setting the appropriate MTU value. It’s worth noting that IPv6 does not support fragmentation, and when using MPLS along with GRE , there is some overhead to consider.

According to the diagram, utilizing an Ethernet interface with a size greater than 1500 could potentially offer a superior solution.

1 Like

IPv6 packets could not be fragmented on the fly during transit across the network, so each router could either forward on an IPv6 packet or discard it. But the source can fragment packets.