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New Member

Another Etherchannel causing STP loops problem

Just encountered this last night.

New configuration - Etherchannel 2 ports from Cisco switch modules installed in IBM Bladecenter to Catalyst6509 switch.

Received the following message sequence on the Bladecenter switch modules:

%PM-4-ERR_DISABLE: channel-misconfig error detected on Gi0/17, putting Gi0/17 in err-disable state

%PM-4-ERR_DISABLE: channel-misconfig error detected on Gi0/18, putting Gi0/18 in err-disable state

%LINK-3-UPDOWN: Interface GigabitEthernet0/17, changed state to down

%LINK-3-UPDOWN: Interface GigabitEthernet0/18, changed state to down

%LINK-5-CHANGED: Interface GigabitEthernet0/17, changed state to administratively down

%LINK-5-CHANGED: Interface GigabitEthernet0/18, changed state to administratively down

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

My etherchannel configs:

Bladecenter

int range gig0/17 -18

switchport mode access

switchport access vlan 102

duplex full

speed 100

channel-group 1 mode on

interface port-channel 1

switchport access vlan 102

switchport mode access

Cat6509

set vlan 102 6/8-9

set port speed 6/8-9 100

set port duplex 6/8-9 full

set trunk 6/8-9 off

set port channel 6/8-9 mode on

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

I checked my Etherchannel configurations on both switches and I should've seen a channel established. Then all of a sudden, Bladecenters on the same VLAN began to err-disable their switch ports. I started seeing 'Duplicate Address' messages and EIGRP neighbor change messages in syslog. I knew I had some sort of STP loop occurring, if that was what was happening at that time.

My questions:

1. What could the switches have seen to say that the channel was misconfigured? Where would I find this information?

2. If the Bladecenter switch ports were admin down via software, then how come I still saw STP loop symptoms? I figure the shutdown state would have stopped or halted any STP calculation issues.

10 REPLIES
Purple

Re: Another Etherchannel causing STP loops problem

I would check the links for any errors , also check to see where the spanning tree root is for the vlans on that channel . One of the dangers of forcing on the channels is that you can get stuff like this , I always set the channels up dynamic non-silent and let pagp do its thing .Have never had a etherchannel problem and we have the same setup with a 6500 going to many bladecenters with cisco igesm switch cards. There is a command to see why it err disabled , show interfaces status err-disabled" .

Hall of Fame Super Bronze

Re: Another Etherchannel causing STP loops problem

Jeffrey,

When configuring etherchanneling in CATOS, you need to bundle the ports and turn the etherchannel mode on different commands.

You have one command there with set port channel 6/8-9 mode on but you also need this command 'set port channel 6/8-9'

Try that and let us know. To verify etherchanneling in CATOS type the command 'show port channel'.

___

Please rate helpful posts.

Thanks

New Member

Re: Another Etherchannel causing STP loops problem

I entered just 'set port channel 6/8-9'. The only change was the AdminGroup number. I looked over the configuration and saw no change in the original 'set port channel' statement.

The 'show port channel' output:

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

6/3 notconnect on 148 802

6/4 notconnect on 148 802

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

6/9 notconnect on 151 805

6/10 notconnect on 151 805

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

6/15 notconnect on 149 808

6/16 notconnect on 149 808

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

New Member

Re: Another Etherchannel causing STP loops problem

Remove VLAN membership 102 on either of both sides.

New Member

Re: Another Etherchannel causing STP loops problem

> Remove VLAN membership 102 on either of both sides.

What would removing it from the VLAN prove? I need to assign it to a VLAN. I'm not trunking.

Hall of Fame Super Bronze

Re: Another Etherchannel causing STP loops problem

Correct,

The Admin group number bundled the ports together. Now go to the IBM switch and issue a shut then 'no shut' command to remove the err-disabled state.

Re: Another Etherchannel causing STP loops problem

As far as STP is concerned, the message means that the channel keeps receiving BPDUs from two different source mac addresses. I'm not a big fan of this feature, but here, it means that the remote port is probably not bundled correctly: the channel is broken up in at least two different interfaces, each sending its own BPDU.

Regards,

Francois

PS: STP is not the problem here, it is just detecting an error.

New Member

Re: Another Etherchannel causing STP loops problem

I have just had the same problem myself.

I seem to recall there was a spanning tree feature that helped prevent this exact problem. Can't remember it off the top of my head. Will look into it

New Member

Re: Another Etherchannel causing STP loops problem

I seen this exact issue and error on 2 of my 6500's runnning IOS. I was missing the "Interface port-channel 1 on one side. What is its equivelint on CATOS? Maybe that answer will reolve the issue.

New Member

Re: Another Etherchannel causing STP loops problem

To configure etherchannel on CatOS, the command would be 'set port channel '. That's it.

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