Re: [gentoo-user] {OT} ISP requires MTU below 1500?

[Grant]

>> 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