Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Webcast-Catalyst9k
New Member

Different Spanning-Tree Implementation on Same VLAN

I'm trying to determine how running rstp and ieee iterations of STP in the same VLAN effect root bridge election.

It was my understanding if this mismatch occurs, the switch running rstp reverts to standard ieee.

Is that true?

I have 2 switches who think they are the root bridge for VLAN0X:

SW1

VLAN0X

Spanning tree enabled protocol rstp

Root ID Priority 32768

Address 001x.xxxx.xxxx

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

SW2:

VLAN0X

Spanning tree enabled protocol ieee

Root ID Priority 32768

Address 00dx.xxxx.xxxx

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

What are the ramifications of this situation?

Any overtly negative consequences?

Thanks!

2 REPLIES

Re: Different Spanning-Tree Implementation on Same VLAN

RSTP and STP use exactly the same rules to determine the root bridge. In fact, except for some very few fields (version type flags), the RSTP BPDUs is exactly identical to the STP BPDU. It looks like your two bridges just can't exchange BPDUs. Hard to say why without more information.

Regards,

Francois

New Member

Re: Different Spanning-Tree Implementation on Same VLAN

Thanks for your timely reply.

It seems that this situation only occured in 2 shared VLANs out of many on these 2 switches. I'll investigate further.

Regards,

Joe

98
Views
4
Helpful
2
Replies
CreatePlease to create content