I'm not sure if I am in the correct section.
We have an MPLS network with DS3s. From what I understand (and correct me if I am wrong), MPLS puts 4 bytes on the packet. Our serial has an MTU size of 4470. Our Ethernet has an MTU size of 1500.
Do I need to change the MTU size, and if so on which interface do I need to make this change. My thinking is to change it on the serial interface (MTU => 4466).
Am I right in my assumption?
When doubts with mtu size, try pings with DF bit set, size 1500 end-to-end.
first of all, if you are an MPLS user, there is no four bytes, just regular IP packets.
Differently if you were an MPLS SP.
Then, you don't need to change anything anyway, the large MTU on the serial is never used, but leave it as it is anyway.
Hope this helps, please rate post if it does!