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I currently have an interface on each switch configured as a trunk between the two switches. I want to now add another interface on each switch to increase the bandwidth between the two. I am thinking about using a port channel, and assigning these ports to the port channel. Will I lose connectivity (temporarily) between the two switches when I do this?

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  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide your own answer and accept it.
    – Ron Maupin
    Aug 7 '17 at 12:12
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Best way (no headache) is to default and shut the member interfaces , create the port-channel , add the member interfaces to the port-channel , no shut and only after that add the trunk configuration on the port-channel (the vlans). There are numberous issues and tricks even when working between switches from the same vendor , like surprises after a reboot when you get different configurations between the port-channel and the member interfaces , leaving you with error-disabled interfaces or unbundled from the Po.

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  • Thanks for the responses. I tested this out on non-production switches and it definitely loses connectivity.
    – Herb Long
    May 13 '16 at 14:21
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The link will probably glitch when you do this, and if you make an error, you will likely send ports into err-disable. The real way to do this is to shut the ports down, build the port channel interface, add the ports to the channel, then bring up the ports.

Also, understand that you will not increase the usable bandwidth for a single data flow. Each flow will only use one of the links in a port channel.

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  • Thanks Ron for your input. When you say a glitch even if I didn't make a mistake, are you saying I would lose connectivity between the two switches from how they are working no to when they are in etherchannel mode?
    – Herb Long
    May 12 '16 at 20:10
  • Even in the best scenario, it will probably drop some frames.
    – Ron Maupin
    May 12 '16 at 20:25
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Expect to lose connectivity - briefly. Configure a port-channel interface on both switches and configure it as a trunk. You might try and specify dot1q trunk.

Configure the new ports with channel group and set mode to "on" and trunk mode. Shutdown the interface via the command line. Do the same on the near side switch. unshut on the far end, then unshut on the near end.

Done. If you don't shut/no shut the interfaces - they may never come up as they will be errdisable.

Both sides mode "on". Shut/No shut.

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