Mailing List Archive: 3560E Migrating from a single uplink to a port-channel on a trunk port with several VLANs

Hello,

Have an old C3560E that is uplinked to another switch using a single 10G interface.

The existing uplink interface is a trunk port and it carries 40 VLANs.

I want to migrate it to use a port channel while avoiding downtime.

Plan right now is to create the port-channel interface on both ends, duplicate the configuration from the existing interface and then plug in the 2nd cable.

I expect that spanning tree will block the port-channel and nothing bad will happen.

Then I will shut down the existing port which should change the port-channel from blocking to forwarding at this point I can just add the original interface to the port-channel.

I've been successful doing things like this on various cisco platforms over the years but never specifically with a 3560e.

Any order of operations sort of things to look out for in a scenario such as this?
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Hi,

On Fri, May 08, 2020 at 05:28:04PM +0000, Drew Weaver wrote:
> Plan right now is to create the port-channel interface on both ends, duplicate the configuration from the existing interface and then plug in the 2nd cable.
>
> I expect that spanning tree will block the port-channel and nothing bad will happen.
>
> Then I will shut down the existing port which should change the port-channel from blocking to forwarding at this point I can just add the original interface to the port-channel.

The general plan is sane.

Now, there is spanning tree involved, so you'll see more or less downtime
still.

If you do rapid-pvstp (which I generally recommend), make sure that all
edge ports (= not linked to other switches) are properly tagged with
"spanning-tree portfast". Otherwise, they might see a "topology has
changed, re-learn port status" cycle, leading to downtime.

No idea about MST, won't touch that stuff with a pitchfork.

gert
--
"If was one thing all people took for granted, was conviction that if you
feed honest figures into a computer, honest figures come out. Never doubted
it myself till I met a computer with a sense of humor."
Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany gert@greenie.muc.de

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