rstp & rapid-pvst compatibility

[subhojithalder198]

Hi,

We connected 2 no 3750 Switch via Fiber cable, 1 switch is running rstp , another one is running RPVST

Is there any performance problem/Broadcast issue can happen

How to check whether any problem / performace issue  is presently not happening

Br/Subhojit               

[Peter Paluch]

Hi,

If you have interconnected two Catalyst 3750 switches, I do not see how one of them can run only RSTP and the other Rapid-PVST. On Cisco switches, there is only PVST or Rapid-PVST - Catalysts have no option of running a global RSTP for all VLANs.

Can you better explain your issue?

Best regards,

Peter

[subhojithalder198]

HI,

Sorry for earlier input.

1 3750 switch is having PVST & another is having RPVST

Pls suggest whether any performance issue can happen/stp loop/delay in STP convergence

Br/Subhojit

[Haihua Rong]

Hello Subhojit,

RSTP is able to interoperate with legacy STP protocols. However, it is

important to note that the inherent fast convergence benefits of RSTP

are lost when it interacts with legacy STP.

For details about how both protocols interoperate, please see following

documents:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper0918

6a0080094cfa.shtml#comp802

Haihua

[daniel.dib]

You are probably running PVST+ and RVPST+ but that is semantics. Is there a reason why you can't run RPVST+ on both?

The fast convergence of RPVST+ is based on synchronizing the topology. That does not work when mixing versions. The RPVST+ switch should detect that the other switch is running PVST+ by the incoming BPDUs. It would then revert to sending 802.1D BPDUs on that interface and rely on timers instead of synchronization.

Daniel Dib
CCIE #37149

[gettofayoyiwajide]

This really makes a lot of sense thanks Daniel