Switchport mode change

[John Blakley]

I've got a simple question I think. I'm preparing some servers to get moved over to a different VLAN. I have a port that's provisioned only for my laptop as a test port. I noticed that if I have a constant ping to my laptop, and I change the port mode from access to trunk, I lose connectivity until the port becomes "available" again. It's almost as long as if I connected a new device to the port. It then comes back up, and shows me that it's trunking.

I don't know if I should enable portfast on the port to keep this from happening, but the thought was that in preparation for moving the servers, we could go ahead and trunk the ports that needed to be trunked (VMWare servers, etc.). I don't think this will be the case, and I think we'll have to do this after hours.

Any suggestions?

Thanks!

John

[Jon Marshall]

John

I would do this out of hours as you suggest just to be on the safe side. However there is a command

spanning-tree portfast trunk

which is useful when you are connecting servers (ie. not switches) that are running 802.1q to your switches. The command acts just like portfast does but for trunk ports rather than access ports.

Jon

[John Blakley]

Thanks Jon. Would you suggest that I switch over all of my servers to ports with portfast enabled? Either in trunk or access mode, or should I just do the trunk on those that have the VM servers on them?

Thanks for the response!

John

[Jon Marshall · Accepted solution]

John

If your servers are not running VMWare ie. they are just single servers then absolutely yes you should set "spanning-tree portfast".

If your servers are running VMWare and they need to connect to the switch via an 802.1q trunk then again yes you can use the "spanning-tree portfast trunk" command. When you do this though you need to be very sure you have no chance of creating any loops. If you have any doubts with the VMWare servers then don't set portfast but be aware it will take approx 50 secs for the interface to come online.

Clients should also have "spanning-tree portfast" set.

Edit - just be aware that adding/removing config like this on switchports really should be done out of hours. Clients not such an issue but servers, only you can really say how important even the slightest blip is.

Jon

[John Blakley]

Thanks Jon!