etherchannel changes

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Jun 5th, 2008
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I need to change the allow vlans in remote on an etherchannel between two catalysts 6500 (IOS), can i have problems? I thought that the channel can be instable when you change the config on one site and then on the other site. What is the way to go and to add the allowed vlans.

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Edison Ortiz Thu, 06/05/2008 - 11:44
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Spanning-Tree will re-converge when you make that change on the link. A brief interruption may occur so it's best to do it within a maintenance window.



pbogaerts Thu, 06/05/2008 - 12:21
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Thanks, but should i begin with adding the allowed vlans on the trunk ports and then on the port channel ? Can i configure one site and the the other ?

Ryan Carretta Thu, 06/05/2008 - 12:29
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What is the platform? On the 6k, for example, you can make the change on the port-channel logical interface and the config will propagate down to the member interfaces. On a 3750, the change would need to be made on the member interfaces (you can do this with interface range all at once).

pbogaerts Thu, 06/05/2008 - 12:54
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It is a channel between a cat6509 & cat6506 with a sup720, the allowed vlans are now configured on both the ports and the port-channel.

So whn i first change the port-channel and then on the ports it would be ok.

Ryan Carretta Thu, 06/05/2008 - 13:04
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You shouldn't need to change the config on the physical ports in the channel. This should happen automatically when you config the logical interface.

Kevin Dorrell Thu, 06/05/2008 - 13:32
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It should be fairly safe to change the VLAns allowed on the channel trunk. You should do this on the channel interface rather than on the individual links. I have never (yet!) had any instability from doing that,

What can become unstable is when you play about with the channel mode of the links. For example, if you have "on" at one end and "desirable" at the other, then the Spanning Tree can break down. If there is a redundant path as well then it could be disastrous.

Kevin Dorrell



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