PVST with do1q encapsulation?????

[azmath.hk]

Hi,

our switch has been configured PVST with dot1q encapsulation on trunk port....

Since PVST is incampatable with dot1q encapsulation, how this switch has been working from long time?

Please need your valuable inputs...

Khan.

[bjw]

Well, this is strange....... Any Cisco folks out there care to step in? I first thought that PVST instances where just local to this switch, like a stand-alone. I can't see redundant patch blocking on this switch. If in fact this switch is not redundant-pathed to a core/dist switch then you might've got lucky in that this switch is forwarding all vlans out all ports and that upstream PVST+ switches are taking care of loop detection/prevention external to this switch.

Maybe try a "debug spanning-tree events" session would help show if anything outside of this switch is responding to BPDUs?

Also send the output of "show spanning-tree summary"

[bjw]

Khan,

After seeing a couple of other threads and a few vague references I feel that PVST really means PVST+ on all recent platform IOSs.

If you do a

switch>conf t

switch>spanning mode ?

Command you'll see that PVST+ doesn't exist, it only references mast, pvst and rapid-pvst

This is a cosmetic anomaly and can be ignored.

[bjw]

pardon the typos, mast s/b MST

[azmath.hk]

Than you very much for your help...

Can you please tell me that in this switch. Is it possible to have PVST as a default configuration? One more thing Is it possible to run both CST and PVST in switch network? Please advivce..

Regards,

Khan

[azmath.hk]

waiting for your comments...

[bjw]

Khan,

CST = all vlans in one STP instance - I believe you need to look MST/MST regions to get to CST on the network edge.

See the 2 following docs.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfc.shtml

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a00807b075f.shtml

[azmath.hk]

the above links are very helpful....

Could you please tell me is it possible to have PVST as a default configuration in a switch especially in our case...our guys are saying that its a default STP configuration as no one has configured PVST its beeen there since we have introduced this switch in a network....Please advice...