topic Re: MSTP problem in Switches, Hubs, and Modems

MSTP problem

lipos — Fri, 03 Dec 2010 17:15:51 GMT

I'm a Cisco guy and I'm a bit struggling to understand HP MSTP vs PVSTP on Cisco.

Here's my config from both switches:

trunk 23-24 Trk1 Trunk

vlan10
name 10
untagged 10
tagged Trk1

vlan11
name 11
untagged 11

span-tree
span-tree Trk1 pri 4
span-tree config-name "MSTP"
span-tree config-rev 2
span-tree instance 10 vlan 10
span-tree instance 11 vlan 11
span-tree pri 0

What I'm trying to achieve is normal PVSTP configuration similar to the one under Cisco.
I need STP per VLAN and I understand that unsed HP I need to assign VLAN to MSTP instances manually, but still after doing it, I see some confusing output like this:

sh span inst 11

...
10 100/1000T 20000 128 Root Forwarding 001ffe-479740
11 100/1000T 20000 128 Alternate Blocking 001ffe-479740
12 100/1000T Auto 128 Disabled Disabled
...
Trk1 20000 128 Alternate Blocking 001ffe-479740

Why do I see Trk1 and port 10 status under instance of vlan11?? Trk1 and port10 is not a part of this VLAN and therefore instance..

Any idea?

Re: MSTP problem

Richard Brodie_1 — Fri, 03 Dec 2010 19:08:08 GMT

Nothing you do in the vlan section affects the spanning tree configuration. All of the ports exist in all of the instances.

What you have to do is to tweak the instance priorities of the switches and ports to get a sensible set of trees, then map your VLANs onto that.

http://blog.ine.com/2010/02/22/understanding-mstp/ is a good introduction to the topic. Unfortunately MSTP and PVSTP are rather different beasts. Good luck.

Re: MSTP problem

Pieter 't Hart — Mon, 06 Dec 2010 09:40:36 GMT

MSTP is totally different from PVSTP.

MSTP is designed to have the same STP-topology for all vlans that belong to an MST-instance.
You will understand this is contradictionary to a per-vlan topology (PVSTP).

If you want simmilar behavour, then for every vlan added to your network you need to create a separate MST instance.

Eventually you will run into a maximum of MST-instances allowed on the switch, depending on model.

Re: MSTP problem

lipos — Mon, 06 Dec 2010 09:56:02 GMT

Thanks.
I though so and just needed to confirm it.
It's official now, HP needs to add PVSTP if they want to be successful then.

Re: MSTP problem

Pieter 't Hart — Mon, 06 Dec 2010 10:26:43 GMT

Don't just blame HP!

>>> Both PVST and PVST+ protocols are Cisco proprietary protocols and they cannot be used on 3rd party switches <<

Re: MSTP problem

lipos — Mon, 06 Dec 2010 10:46:52 GMT

I'm not blaming HP, I'm just saying that they have a good product with awesome prices and I would move to HP in all my DC as access layer switches right away. Without PVSTP, HP Procurves is still a question.

Re: MSTP problem

lipos — Mon, 06 Dec 2010 10:49:18 GMT

"Both PVST and PVST+ protocols are Cisco proprietary protocols and they cannot be used on 3rd party switches, although Force10 Networks and Extreme Networks support PVST+"

Juniper: http://gul-tech.livejournal.com/987.html

Re: MSTP problem

Pieter 't Hart — Mon, 06 Dec 2010 11:02:32 GMT

If you move to HP, you won't have a problem then, just move to MSTP ;-)

MSTP an PVSTP can coexists in a network.
HP and Cisco have whitepapers on this subject.
In a homogenouos network designed with attention to STP topology, it's just a matter of choise wich one to use.
But right now your problem is just in interconnecting the devices.

Beware HP also doesn't talk VTP, so each vlan you create on Cisco must also manually be added to HP (HP talks GVRP).

Re: MSTP problem

lipos — Mon, 06 Dec 2010 11:17:57 GMT

I will give it a try, but still I if HP would be able to get PVSTP as other did a lot of people would just move to them.
HP if you can hear me please add this functionality :) (Even if it's going to be called HP-PVSTP :)