STP Configuration Between Cisco and HP

[Mansoor Hafeez]

Hi

We are in a progress where we have to connect the HP Switches to the Cisco Switches on the Distribution Layer.

On Distribution Layer the Spanning Tree Protocol we are running is PVRSTP+. Now as per our recent studies, we have figured out that the HP Switches does not support/interoperate with Cisco PVRSTP+. Now we have number of options to overcome this issue.

1. Downgrade from PVRSTP+ to MSTP or RSTP.

2. Switch off the spanning tree on HP Switches as well as VLANs on Cisco those will be extended to HP Switches.

The question is does anyone has experience where both Vendors are running together with the setup which I have currently running i.e. Cisco PVRSTP+ as Primary Root? If yes than if possible configuraiton can be shared?

Thanks in advance

Mansoor Hafeez

[cadet alain]

Hi,

on Cisco switches you have 3 spanning-tree modes:

-PVST+

-RPVST+

-MSTP

bu not pure RSTP and I don't think going from RPVST+ to MSTP would be considered a downgrade.

I wouldn't get rid of spanning-tree because you could run into problem later if you stick to L2 design but you could choose a L3 design if the switches support.

Regards.

Alain.

[Mansoor Hafeez]

Hello Alain

Thanks for the answer. The problem is we cant go with Layer 3 between Cisco and HP although they both supported Layer 3.

The Spanning Tree must need to be adapted. As far as I have learned, hp supports MSTP and RSTP. If I downgrade the RPVST+ with RSPT than I believe interoperability will not be an issue.

But again if anyone is running the setup which I have currently running, his experience will be highly appreciable.

Mansoor

[Antonio Knox]

I don't see how running L3 on the 3560 would pose an interoperability issue with the HP switch.  Turning on L3 will not affect how the switch communicates with the HP switch on L2.  It's added added functionality, it won't interfere with your current L2 solution whether you choose RSTP or MSTP.

[Mansoor Hafeez]

I already have tested that running together RPVST+ on Cisco with RSTP or MSTP on HP will disrupt/block the traffic unless or until you switch off the Spanning Tree on HP.

As I mentioned earlier, Layer 3 is not possible to use between HP and Cisco. I only have to adopt some solution belonging to Layer 2.

Mansoor Hafeez

[Antonio Knox]

I'm not debating that RPVST+ works on HP (it won't because RPVST+ is Cisco proprietary).  What I'm saying is that running L3 on the 3560 won't break layer 2.  I recommend you go with the standard protocols at L2 when connecting between multiple vendors.  RSTP and MSTP are your only choices if that is all that HP switch supports.

I would recommend RSTP as MSTP can be a hassle to manage depending on your network setup.

Message was edited by: Antonio Knox

[Mansoor Hafeez]

Now the question is if I will change the mode from RPVST+ to RSTP on Cisco, what will happened to the switches those are running the RPVST+ mode in the network. Do i need to change the mode there as well or chaning on Primary Root will be enough?

I believe changing the mode will also disrupt the traffic for some time.

Mansoor Hafeez

[cadet alain]

AFAIK  Cisco switches support RPVST+ and not pure RSTP so I think the only solution you got is MSTP.

Regards.

Alain.

[will.cullen]

There is this command available on the HP switches

spanning-tree priority xx force-version rstp-operation or STP-compatible, the value xx can be upto 15 which equals a priority of 61440 ( 15 x 4096).

[lamav]

Mansoor, I recently wrote a detailed white paper, which included testing and debugs, regarding how 3rd party switches interoperate with Cisco's PVST+ - rapid or otherwise - when running the open standard of STP (802.1d-2004, which incorporates 802.1w RSTP). Although the 3rd party switch used in my testing was a Dell Power Connect 6200, the findings of the test apply to any switch that runs the 802.1w version of RSTP.

Moreover, I wouldn't categorize a migration from rapid-PVST+ to MSTP as a "downgrade." I actually would consider it an upgrade that results in less traffic and switch resources being unnecessarily utilized.

Attached is the document or you can go to the Documents tab on CSC and see it there.

Hope this helps...

Victor Lama

[Mansoor Hafeez]

Thanks a lot for the document. It really helps me understand the interoperability between devices.

Now if I change the mode from Rapid-PVST+ to MSTP, than what will happen to the devices which are currently configured as either RPVST+ or RSTP.

Will they be still able to connect to the Primary Root?

Mansoor Hafeez