I’m using a C3750 on which I would like to modify the IPv6 MTU for a GRE tunnel interface.
I’m running a 12.2(46)SE release of IOS and the “ipv6 mtu” command is not available.
Is there a way to change this value ?
Why I need this change ?
I’ve a GRE tunnel configured between this 3750 and a Juniper router. I noticed that a ping (IPv4 & IPv6) with a packet larger than 1414b didn’t work. (maybe due to the equipments between those 2 routers, fw, ipsec tunnel, etc…but not sure why...)
I’ve changed the MTU value for IPv4 on both sides (set to 1414b), after this change ping (ipv4) is now working fine with any packet size.
I would like to do the same for the IPv6 packets. I can easily do it on Juniper side but wasn’t able to do it on the 3750.
Right now the default MTU for IPv6 packet on the Cisco side is 1514b.
I already tried to set this value on the Juniper, but it doesn’t work.
(This tunnel is used for an OSPF3 session to progagate ipv6 routes, the OSPF session is stuck in an EXCHANGE state. Cisco router send its DBD but it seems that packets never arrive on the Juniper and the Cisco try to retransmit the DBD again and again...)
Really appreciate if someone can help,