Is there any easy way to “hint” to an EoIP that the underlying link is a particular MTU (the data path the EoIP tunnel is passing over).
I have an EoIP going over a switch to the where the MTU is running at 9000 (other services pass over this connection), the ISP themselves support higher MTUs but somewhere between the two sides of the EoIP the MTU drops back down to 1500. I need a MTU of 1500 be maintained through the EoIP so there will be fragmentation of the larger packets.
The problem as far as I can see is the EoIP is using the interface’s MTU as its hint as to when it has to fragment the ethernet packets and and how small to fragment the packets. This was discovered as the internet circuit is going directly into the EoIP router on the far side and hands off at a 1500 MTU.
One way I’ve seen to do this is to first establish an IPIP tunnel with a MTU of 1400 and then put the EoIP on top of that, any way to avoid the extra overhead of a 2nd tunnel just to provide a MTU hint to the first tunnel?