Port-channel counters in 3750

Unanswered Question
Mar 22nd, 2008

In a 3750 running 12.2(40)SE I have configured 2 port-channel groups (po1 and po2) linking to 2 different 6506/6509 switches. What I see is only one port-channel interface (po1) counters is working. Other one is always showing 0 input and 0 output rates although it's passing the traffic. From 6500 switch I can see the port-channel interface counter is increasing. How do I configure the 3750 so both port-channel group interface counters work?


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Edison Ortiz Sat, 03/22/2008 - 13:34

You may be experiencing a common Spanning-Tree behavior. One port (or bundle port on this case) is forwarding while the other port is in blocking mode. This is to avoid a network topolody loop.




Yang Xia Sat, 03/22/2008 - 13:54

Thanks for the reply Edison. In the 3750 both po1 and po2 are in forwarding states. However po1 is blocked his upsteam switch (6506) and po2 is forwarding to a 6509. Since traffic is using po2 interface I'd expect po2 interface counter should increase. But it's not the case. Also the broacast counter is acting wierd showing "Received 18446744073698874624 broadcasts (726 multicasts)".

#show int po1 | incl rate

Queueing strategy: fifo

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 29000 bits/sec, 9 packets/sec

#show int po1 | incl broadcast

Received 18446744073698874624 broadcasts (754 multicasts)

#show int po2 | incl rate

Queueing strategy: fifo

30 second input rate 0 bits/sec, 0 packets/sec

30 second output rate 0 bits/sec, 0 packets/sec

#show int po2 | incl broadcast

Received 18446744073709535763 broadcasts (7445 multicasts)

Yang Xia Sat, 03/22/2008 - 21:03

spann tree log is attached here.

Topolog is: 3750-----6509

| |


The blocked ports in 6506 are the port channel ports.

Thanks Edison!

Edison Ortiz Sun, 03/23/2008 - 08:42

Some information there but not enough. I need the entire spanning-tree output, not just the summary.

Couple of things I noticed:

1) You have one switch running in PVST+ while the other two on PVST.

2) The PVST+ is behaving as it should, blocking Vlan 70,71 and 75 when having multiple links towards the root while the switches running PVST aren't blocking any ports even if the switch itself isn't the root for such Vlan. You can see this behavior in the 3750 and the other 6509.


Yang Xia Sun, 03/23/2008 - 13:16

6506 is running hybrid OS and pvst+ is the default. There is no pvst option in hybrid OS.

I included everything from show spantree in the log. It's fairly long list.

Back to my original question, I suspect interface input/output rate counters are showing 0s is because of the bug in IOS. I see the total packets input/ouput counters are increasing.

Thanks Edison!

Edison Ortiz Sun, 03/23/2008 - 16:37

Output looks fine. You may be onto something with the counters. What version of IOS are you running on the 3750 switches?

Yang Xia Sun, 03/23/2008 - 17:12

Running image on the 3750 is c3750-ipbasek9-mz.122-40.SE.bin. I may want to give the latest 122-44.SE1 a try.

#sh ver | incl IOS

Cisco IOS Software, C3750 Software (C3750-IPBASEK9-M), Version 12.2(40)SE, RELEASE SOFTWARE (fc3)


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