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Re: MTU and Postfix

04.09.2011 12:40, Camaleón:

>> I'm still monitoring this but if this is the "cure" to prevent such
>> errors, are there any expected drawbacks for lowering MTU "system-wide"?
> (...)
> Mmm, no replies yet...
> Does it mean then that there are no gotchas to care about in setting a 
> MTU value of 1400 for a bonded interface? :-)

I don't see any gotchas besides the obvious one: the throughput is
decreased somewhat, since on average more packets are needed to transmit
the same amount of payload.

OTOH, in my experience, when you can work around transmission problems
by lowering the MTU, almost always someone has b0rked his packet filter
and throws away those ultra-evil ICMP packets like "Fragmentation
Needed" or "Time Exceeded in Transit" etc.
If you're sure you're not the one killing ICMP and the problems only
occur with specific sites, it might be helpful to have the
administrators of those sites check their "firewall" configuration.


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