KICKING MYSELF IN THE A**!!!

Unanswered Question
Aug 10th, 2007

OK, I forgot to add a stupid vlan to some trunk ports that were bundled in an ether channel. So, what did I do? I added it to the allowed vlans for each port -- ONE AT A TIME!. Wrong!!

As I would add the vlan, the port would fall out of the etherchannel bundle and be placed in a "suspended" state. After I did it to all 3 of my uplinks, the etherchannel died altogether.

What was I supposed to do? ADD THE VLAN TO THE PORT CHANNEL, NOT INDIVIDUAL TRUNK PORTS IN THE CHANNEL!

I have this problem too.
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mohammedmahmoud Sat, 08/11/2007 - 00:03

Hi,

When changing the allowed VLANs per member interface the switch will give you the "(vlan mask is different)" message and suspend the port, which is logical as all the members must be compatible with each other, the correct action is as you said is to control the allowed vlans per the whole port channel and not individually.

HTH,

Mohammed Mahmoud.

lamav Sat, 08/11/2007 - 03:06

Yes, Mo, I know that now. I ealized it the hard way yesterday. I guess its one of those things that you may not think about if you havent experienced it before. LOL

lamav Sat, 08/11/2007 - 03:44

On the other hand, it may not be as obvious as all that. I mean, I didnt add the trunk to the port channel port simply because it didnt occur to me to do it that way until about an hour into troubleshooting, I thought I had an L2 loop at first. So I made a mistake.

But going back to how different switches work, the 6513 CatOS switches are not like that. You can add the vlan to the individual trunk ports, as I tried to do on the 4506 yesterday.

And one would think that, having set the channel mode to desirable, that any change in a trunk port's allowable vlans would indeed cause a temporary suspension, but that once the other ports are matching (as you configure those to allow the additonal vlan), the channel mode would renegotiate to create the etherchannel once again.

I wonder if other manufacturer switches behave this way. I wonder if this is a Cisco thing or even just a Cisco native-IOS quirk.

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