05-25-2015 04:54 AM - edited 03-08-2019 12:10 AM
Hello,
I have two switches running as root for 2 instances in MSTP, each one is root for a different instance:
vlans | root | |
MST1 | 6 30 | A (2960X) |
MST2 | 2 49 50 168 | B (3750G) |
and then another switch model 3750G (called Switch) connected to both roots via 2 dot1q trunks, one to each root.
So, the situation which I expected was to have trunk ports as:
root port for the vlans in MST1 for the port connected to A
root port for the vlans in MST2 for the port connected to B
Switch | Trunks for Switch to Root | vlans to be root port | ||
Switch | Gi1/0/23 | Root A | gi2/0/47 | 6 30 |
Switch | Gi1/0/24 | Root B | gi1/0/21 | 2 49 50 168 |
However, what I find is that both roots find themselves as root for every instance and not Root A root for MST1 and Root B as root for MST2.
For example, the roots for Root A is always itself:
Primary#sh spanning-tree root
Root Hello Max Fwd
MST Instance Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
MST0 4096 1ce8.5d36.8c80 0 2 20 15
MST1 4097 1ce8.5d36.8c80 0 2 20 15
MST2 28674 1ce8.5d36.8c80 0 2 20 15
And for Root B, it finds itself for MST1-2 but not for MST0:
Secondary#sh spanning-tree root
Root Hello Max Fwd
MST Instance Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
MST0 4096 1ce8.5d36.8c80 20000 2 20 15 Gi1/0/22
MST1 28673 001b.2ad9.8300 0 2 20 15
MST2 24578 001b.2ad9.8300 0 2 20 15
Is this normal? Why both roots don't recognize themselves in MST1-2?
I attach spanning-tree summary for both roots and configs for 3 switches (A y B, and Switch which is not root).
Thank you very much in advance. Please, any comments or questions will be grateful.
Solved! Go to Solution.
05-25-2015 06:25 AM
Hi,
Your switches are not in the same MSTP region. Your SwitchA uses revision 1 while the other switches lack this command and use revision 0 as a result (this is confirmed by their output of the show spanning-tree mst configuration command). For switches to be in the same MST region, they must match in all configurable parameters, that is, region name, revision number, and VLAN-to-instance mappings.
To solve your problem, either add the revision 1 command to your remaining two switches, or remove this command from SwitchA's configuration.
Best regards,
Peter
05-25-2015 06:25 AM
Hi,
Your switches are not in the same MSTP region. Your SwitchA uses revision 1 while the other switches lack this command and use revision 0 as a result (this is confirmed by their output of the show spanning-tree mst configuration command). For switches to be in the same MST region, they must match in all configurable parameters, that is, region name, revision number, and VLAN-to-instance mappings.
To solve your problem, either add the revision 1 command to your remaining two switches, or remove this command from SwitchA's configuration.
Best regards,
Peter
05-25-2015 07:59 AM
Hi Peter,
Yes, I changed revision number to 1 and now it makes sense.
Now I see everything running ok. I suppose when combining Cisco with HP is better to go to MSTP than stay with rapid-pvst and the somehow compatible protocol of HP. This is the reason to try MSTP.
Any advise in migration from rapid-pvst to MSTP?
Thank you very much!!
05-25-2015 09:26 AM
Hi,
You are welcome.
When combining switched from multiple vendors, MSTP is the proper way to go even though maintaining it may be a little more cumbersome.
When migrating from Rapid-PVST to MSTP, well, there have been quite a few thread on that here already. The key takeaways:
Best regards,
Peter
05-26-2015 08:36 AM
Hi Peter, you have been very kind. Thank you for your long reply....
I am very grateful. The best for you!
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