Procurve 2810 - Question on Spanning Tree Protocol

[Steve_NetAdmin]

I'm working on setting up a 2gigabit trunk connection between my three procurve 2810's. 1 with a 2 gig trunk to the next, then from that one to the end. I have rapid spanning tree protocol enabled on all three switches, and created a one port trunk from port to port. 

After much reading I figured that a static "trunk" connection will be less hassle than LACP considering we use multiple VLans. The performance improvement on our iSCSI SAN should make me more than happy to need to mess with LACP. 

If I disable the current "live" port. Will RSTP instantly take over and move the connection to the existing trunk so I can add the additional port? Or will there be dropped packets while it figures out that it needs to use the other connection? 

I'm already planning on doing this outside of business hours so things don't go down, but I thought this would be handy information in a pinch if anyone out there had this knowledge. 

[paulgear]

Hi Steve,

Spanning Tree convergence is not instant. You can adjust the timers down, but not to the point of zero convergence time. However, if you have RSTP enabled and your new trunk is the alternate port to the root, then there should be no reconvergence. You can check this using 'show spanning-tree'.

One of the most common mistakes we see here in the forums is setting link priorities instead of switch priorities. If you haven't set switch priorities, then your root switch may not be the switch you expect. If that is the case on your network, you should organise downtime to set the switch priorities correctly (which will cause reconvergence), and while you're doing that, you might as well install your new trunk and get it all done at once.

There should be no difference in terms of VLANs between a static (HP proprietary) trunk and an LACP trunk. Both can carry VLANs just fine.

[Brad_199]

Paulgear, wouldn't it be pointless creating a trunk group on each switch consisting of only one port?

[paulgear]

Brad_199: Not for the purposes of migration.  If you put your trunk configuration in and then switch over to it, additional ports can be added without impacting spanning tree.