09-25-2013 03:25 AM - edited 03-04-2019 09:08 PM
Dear All,
Please look at the attached picture. Switch 2 upper port is Gb1/1, which is blocked and the lower one is the Gb1/2, which is the root port. I dont't understand why not the upper port become to the root port... Because both of the mentioned port path cost is the same (16), and as I know in this situation the port with the lowest mac address win the election, which is the upper one (the upper port Gb1/1: 0060:4779:E401 while the Gb1/2: 0060:4779:E402)
Could you help me? Thank you
Solved! Go to Solution.
09-25-2013 04:09 AM
Hi,
SPT follows the following order to selecte root port. port number is the last.
1, lowest total paht cost
2, lowest neighboring switchID
3, lowest port priority
4, lowest port number
HTH,
Lei Tian
09-25-2013 04:09 AM
Hi,
SPT follows the following order to selecte root port. port number is the last.
1, lowest total paht cost
2, lowest neighboring switchID
3, lowest port priority
4, lowest port number
HTH,
Lei Tian
09-25-2013 04:30 AM
Oh, I see,
Thank you very much
09-25-2013 04:37 AM
Hi,
nicely explained here:
http://ciscoiseasy.blogspot.cz/2010/10/lesson-20-spanning-tree-protocol.html
Best regards,
Milan
09-26-2013 05:01 AM
Thank you very much, very useful!
09-26-2013 08:24 AM
Just a quick follow up Mary,
on step 3 when you go to Port Priority as the poster above specified, there are two different settings with this.
Port Priority = 128.(interface number) usually
So for instance, if you have ports fa0/1 and fa0/10, they should be like this.
128.1 and 128.10
If you ever need to modify STP that far, you will need to understand those differences.
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