So 1464 + 28 = 1492 which is your IP MTU for PPPoEoE, which is the normal value you would expect for anyone using a PPPoEoE modem. The standard value for two-box systems with separate modem and router.
Now you probably know all this anyway, but if not: the value 1492 = 1500 - 8 is the IP MTU less the PPPoEoE header overhead of 8 bytes, an overhead which reduces the size of IP packets down from the standard 1500 bytes on the LAN. So you can set your MTU in your router to 1492 or lower, higher is better clearly. You probably don’t need to do anything as 1492 should by the default for any PPPoE user.
Unless that is you are fortunate to have a ‘baby jumbo’, larger MTU link with a PPP MTU of 1500+8=1508, as I do (my IP MTU is 1500=1508-8, not 1492=1500-8, for this reason). I can send/receive full size 1500 byte IP packets, not just 1492 bytes long. Gives me a microscopic edge in performance and a theoretical advantage on the internet which is rather unrealistic.
Neil’s MTU doesn’t have to be so low surely, at 1492 bytes it should be fine. I seem to remember some home routers that have really low default MTU settings for god knows what reason.
I was wanting to ask about people’s experience who have an MTU rather lower than 1492 though. If I start to consider a situation where I’m forced to live with a lower MTU because of L2TP say, then I would like to know what I’m getting into.
My 3G USB NIC ‘dongle’ has a really really low MTU.