Catalyst 2940-8-TT: Performance Problem via 10/100/1000 Trunk

Unanswered Question
Apr 20th, 2010

Hi there,

I use a Cat. 2940 as Access switch in the following scenario: One 100 Mbit Client <> Cat.2940 <>Cat.3750-G12<> Cat.3560-G24 <> 1000Mbit Fileserver. Connection between 2940 and 3750 is established as dot 1.q Trunk; both their corresponding Interfaces are in Auto Mode.

IOS Version is 12.1.(22)EA9

During RX of a 100 MB File, show interface gi0/1 shows that 2940 sends PAUSE Frames via gi0/4 to the the 3750-Interface (PAUSE Output of 2940 Interface and PAUSE Input of 3750 Interface increase syncronously) The network Transfer graph and Rate from the Clients Point of View is definitly suboptimal (max. 3 MB /s average);

Datatransmit from Client to Server shows optimal behavior.

Shuting of Flowcontrol on 2940 stopps the 2940 in sending PAUSE Frames, but there is no Enhancement in the described RX behavior of the 2940.

Setting the 2940-gi0/1 and the 3750 gi0/x in switchport access mode for the client vlan, doesn't change anything to the better.

Replacing the 3750-G-12 with a3560-G24 makes also no difference.

I also haven't found any hint on CCO yet.

Is there any solution to an adequate  RX Rate via a 2940 10/100/1000 Trunk?

Best,

Thomas

I have this problem too.
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tochs Wed, 02/16/2011 - 01:50

Additional note and a possible cause:

All Servers are connected to the Core-Switches via 2 Gbit/s Etherchannels on 3560G-24 Catalysts as Server Access-Switches. It seems, that CDP triggers the 2940 to behave like that.

T.O.

blacktrack Wed, 02/16/2011 - 03:51

Try to force speed to 100 and duplex full.

i have also that kind of problem everything was ok after disbling auto mode.

regards

Hicham Azarou

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