pvst to rapid-pvst and hsrp convergence time?

[gavin han]

current our gateways (6500 switches) are running pvst, we have to change it to rapid-pvst,i also have to update stp root, so that sw-1 is root for odd vlans and sw-2 is root for even vlans. what will be convergence time for pvst -> rapind-pvst & spanning tree root changes? we have to update hsrp priority as well. what will be convergence time for hsrp?

should i change it to rapid-pvst and udpate spanning-tree root 1st and than update hsrp priority for SVIs or do all at the same time?

[Reza Sharifi]

If you don't have a lot of vlans, it is easier if you make one device the root and the same device hsrp active for all vlans and not divide them by odd and even.  If you want to divide them by odd and even you need to make for example sw-1 the root and active hsrp for odd vlans and sw-2 the root and active hsrp for the even vlans. As for how long it takes to converge, it should not take very long, but you would need an outage window to do this in case something goes wrong and you need to troubleshoot and/or revert back.  I would do one task at the time, test and then the other one and test again.

HTH

[gavin han]

Thanks. would 60 seconds be enough outage window for rapid-pvst, spanning-tree root, hsrp change? access switches are already running rapid-pvst so i just need to do core switches. it's our standard to make sw-1 root and hsrp active for even vlans and sw-2 for odd vlans.

[paul driver]

Hello

I would suggest do the access layer first and work you way up to the cores and not to forget to arrange an outage window for the changes

Pleas review this - very helpful -  cco doc

Res

Paul

[Joseph W. Doherty]

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You might want to read: http://blog.ine.com/wp-content/uploads/2011/11/understanding-stp-rstp-convergence.pdf

If you're moving active gateways with HSRP priorities, gateway "convergence time" will be somewhat a non-issue.  Clients won't see a change.  I believe the priority change will start with the next HSRP hello.  Also, don't forget moving gateways with priority may require using the preempt option.

If you're going to load balance odd/even VLANs, you might want to look at using GLBP instead.

Also, when you have multiple gateway on different L3 switches, you can create unicast flooding issues, so beware.

If you're setting active gateway device to be STP root, you'll likely also want to set standby gateway as secondary root.  Actually, as long as your (pair?) 6500s are configured as primary and secondary root, you may not really have to do them by VLAN odd/even (alined with active gateway).  What you want to avoid is some edge switch becoming the root.