>> A while back I was having networking issues. I eventually tried >> drastically lowering the MTU of all the systems onsite and the issues >> disappeared. I always thought the issue was due to the MTU on our >> modem/router. Today I read that AT&T DSL requires a 1492 MTU so I >> increased the MTU of our systems up to 1492 and haven't had any >> issues. Do certain ISPs require you to change the MTU of your entire >> network, or is this likely due to our AT&T modem/router itself? > > AFAIK the MTU is defined for every network interface separately. For an > ADSL connection it is common that a lower MTU is needed because of the > PPPoE header information that is encapsulated in the ethernet frames. > But in that case it is sufficient to lower the MTU just for the WAN > interface that is connected to the DSL modem. > If you don't use protocol encapsulation in your LAN then there should > be IMHO no reason for lowering the MTU of your internal interfaces.
So I should be OK with 1492 MTU on the modem/router and 1500 inside that LAN? That hasn't been my experience but I haven't tried in a while. Wouldn't that lead to fragmentation issues? Admittedly, my understanding of this is weak. - Grant
