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.