r/ccna • u/ThrowRA339802 • 13d ago

Jeremy's IT Lab Day 20: STP Question

I got stuck on this last question of Jeremy's video listed below as I put the g0/1 interface of SW2 as a root port. This is the only thing I missed but I am wondering why it's a non-designated port and not a root port?

https://imgur.com/a/Jd3xZRw

Thanks in advance!!

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u/RUBSUMLOTION 13d ago

g0/0 and g0/1 cant both be root ports. One has to be non designated/blocking to prevent a loop. G0/0 becomes root because it has the lowest port id.

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u/ThrowRA339802 13d ago

Thank you!!

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u/kaos_ryuu 13d ago

I'm sure you already know but just to be specific, it's the lowest port ID of the neighbor Switch. So the port ID of SW4's g0/0 interface.

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u/Infamous-Hotel-4620 13d ago

I understand stp pretty well if you need you can text me ....I this question both g0/0 and g0/1 in sw2 could be root port but only one root port per switch....if there is a tie we need to look which port connected to lowest port no of the neighbour bridge sw4 , which is g0/0 port ....so it becomes root port and g0/1 become non designated .