MTU issues.

[Paul Gildea]

Hi,

We are seeing MTU issues with the ATT network and were just wondering if
you had heard of anything like this happening before? ATT push an MTU of
1430, we apply that to our linux interface and everything works fine.
However when we try and ping with a large packet and the pings fail instead
of fragmenting correctly, we also see input errors on the linux interface.

In some scenarios the input errors never stop (getting thousands of them
every second) after we stop pinging and the modem needs to be rebooted to
pass any traffic again. Changed MTU values to a lot of different things and
this always occurs.

On a private network here (MTU 1404) and Vodafone (MTU 1500) doing the same
thing with the network pushed MTU values causes no issues and everything
works fine. I tested moving away from 1500 on vodafone to lower values and
once the issues reoccurred, same as with ATT.

Libqmi 1.24 and I have seen this behaviour with all modems tested so far:
MC7455, EM7565, EM7511 and Telit LM960A18.

Regards,

--
Paul
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