Wireshark-users: Re: [Wireshark-users] MTU - wireshark showing length longer than.
How did you have the capture buffer set up?
I've had some situations where I had to set it to 100MB when capturing a
10Gb link. I also turn of the updates during the trace.
If you had it set to default, try making the trace with it set to 100MB and
see if there's a difference.
----- Original Message -----
From: "Ant Mitchell" <ant@xxxxxxxxxxxx>
To: <wireshark-users@xxxxxxxxxxxxx>
Sent: Wednesday, November 25, 2009 10:27 AM
Subject: [Wireshark-users] MTU - wireshark showing length longer than.
Hi,
I am new to wireshark and TCP diagnostics in general. I have a problem
with a HP procurve switch that I am trying to diagnose.
I have removed the switch from my config, and now have an xserve
plugged into a centos box, both running 10gb myricom cards.
Both ends have flow control enabled, and an MTU of 9000. I have double
triple checked this.
I have been running netperf tests across the link, mostly from the
xserve to the centos box, and I see wireshark report packet lengths
way in excess of the mtu. The throughput I am getting is about 2900
Mbps.
How is the packet length being reported so large ?, sometimes these
large packets seem to get acked and sometimes they don't , resulting
in lost segments.
The same large packets appear in tcpdump also, so its not a bug in
wireshark.
What should I be looking at ?, how does the packet size get larger
than the MTU ?. A typical size is 8960 for several packets, then 17960
and 20456 and several inbetween.
Thanks
--
Ant
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