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Flowcontrol between 3560 and 2950 does not work?

Configuration:

==============

C3560 Software (C3560-IPBASEK9-M), Version 12.2(25)SEB1, RELEASE SOFTWARE (fc1)

interface GigabitEthernet0/3

description R14 Trunk 50,[100],102,105,199

...

switchport mode trunk

switchport nonegotiate

flowcontrol receive on

end

connected to

============

C2950 Software (C2950-I6K2L2Q4-M), Version 12.1(22)EA6, RELEASE SOFTWARE (fc1)

interface GigabitEthernet0/1

description R01 Trunk 50,[100],102,105,199

...

switchport mode trunk

switchport nonegotiate

flowcontrol receive on

flowcontrol send on

end

Port Gi0/1 on 2950 has sometimes no buffer and drops packets:

============================================================

GigabitEthernet0/1 is up, line protocol is up (connected)

...

Full-duplex, 1000Mb/s, media type is RJ45

input flow-control is on, output flow-control is on

...

193421146 packets input, 2844802437 bytes, 2637 no buffer

0 input errors, 0 CRC, 0 frame, 0 overrun, 2637 ignored

but it never sends a pause packet:

==================================

cs-a2p5#sh flowcontrol

Port Send FlowControl Receive FlowControl RxPause TxPause

admin oper admin oper

--------- -------- -------- -------- -------- ------- -------

Gi0/1 on on on on 0 0

What am I doing wrong? I have realized that this data overload is caused by

server with 1Gbs interface pushing data to server with 100 Mbs interface.

I vould expect it should not affect a trunk with flowcontrol on.

Tomas

1 REPLY
Silver

Re: Flowcontrol between 3560 and 2950 does not work?

By wild guess, is the flowcontrol also enabled at the interface to / at both servers ? If there is only flowcontrol between switches but no flowcontrol at servers then it may create the problem. Please advise more.

Moreover, if you transmit 10 times of traffic to a receiver that it can handle, there may be packet drop and flowcontrol to ask for retransmittion.

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