PVST

alsayed · ‎02-07-2008

Dear NetPro!

what is the Difference between :

PVST

PVST+

R-PVST

MST

IN Wich cases we would use EACH One of theme?

many 10xs

Jon Marshall · ‎02-07-2008

Ali

PVST = Per vlan spanning tree. Each vlan has it own instance of spanning-tree. PVST is for use with ISL links.

PVST+ = same as above but it is for use with 802.1q

R-PVST = Rapid Spanning tree. A lot of the Cisco proprietary features in the original STP like uplinkfast/backbonefast/portfast were incorporated into R-PVST. R-PVST brings convergence times from approx 45 seconds to less than 5.

MST = Allows you to group a set of vlans into a single instance of spanning-tree. MST uses Rapid PVST so it also has rapid convergence times.

That is a very high overview. There are good links on Cisco's sites that cover each in more detail.

I have never used MST but as for the others i would recommend R-PVST if all your switches support it, then PVST+.

HTH

Jon

alsayed · ‎02-07-2008

HI Jon

i have a 3550 Switch with PVST Mode and I COULD Ran spanning-tree portfast and Spanning-tree Uplink fast?how come this:

R-PVST = Rapid Spanning tree. A lot of the Cisco proprietary features in the original STP like uplinkfast/backbonefast/portfast were incorporated into R-PVST..

What about the Covergence of normal Pvst ?

10xs

Jon Marshall · ‎02-07-2008

Hi Ali

The features of uplinkfast/backbonefast/portfast were added by Cisco to try and improve the speed of convergence.

STP, PVST, PVST+ all have the same covergence time, as i say approx 45 seconds. There is little you can do to speed this up.

If you can run R-PVST+ and you have redundant links in your infrastructure then there is no good reason why you shouldn't. Be aware though that any switch that a vlan exists on needs to run R-PVST+ or for that vlan you will default back to normal PVST+ convergence times.

Jon

ehlers.kevin · ‎02-09-2008

Hi,

I've noticed some odd behavior when using pvst+ and rapid-pvst+ with HP Procurve switches. Specifically, spanning-tree would work correctly when using access ports, but not when using 802.1q trunks. Yes, I know it's supposed to work, but I have not observed that.

MST was the only version that worked well with our HP switches.

-Kevin