# Help with practice test question

Member Posts: 42 ■■□□□□□□□□
I'm having trouble understand the answers to this question

I understand that there's 1 designated port per segment, but why is port Fa0/0 on switch B the designated port, and not Fa0/0 on switch A? Both ports are on the same segment, and they are equal distance from the root bridge.

## Comments

• Mod Posts: 11,962 Mod
Wheres the question???
An expert is a man who has made all the mistakes which can be made.
• Member Posts: 42 ■■□□□□□□□□
in the image...
• Mod Posts: 11,962 Mod
I can't see the image, but I think what you are asking is which port is used as the designated port if the root path is equal on both switches. If the root path is equal the bridge id will be used next and the lower bridge id will win.
An expert is a man who has made all the mistakes which can be made.
• Member Posts: 1,693 ■■■□□□□□□□
They are counting the ports on the root bridge(B) as designated ports. Then as networker said, it's the lowest bridge ID if the costs are the same.

port fa0/0 on switchC is switchC's root port and the fa0/0 port on switchA is a root port.

Then between switch A and C, A is advertising the lower Bridge ID, therefore it is the designated bridge on the segment and port fa0/1 is also designated.
There is no place like 127.0.0.1 BUT 209.62.5.3 is my 127.0.0.1 away from 127.0.0.1!
• Mod Posts: 11,962 Mod
All ports on the root bridge become dp on all segements because they advertise the lowest root path cost (0).
An expert is a man who has made all the mistakes which can be made.
• Member Posts: 42 ■■□□□□□□□□
So the port with the lowest mac address on the segment gets chosen as the designated port if the cost if the same? Otherwise the closest is chosen?
Sounds about right to me. Thanks guys
• Mod Posts: 11,962 Mod
Not the port with the lowest MAC, the bridge ID is used. The bridge ID consits of the priority and the MAC address of the switch. It is not the "closest" that is chosen either. It is the lowest cost. A switch can be farther and have a lower cost do to higher speed links.
An expert is a man who has made all the mistakes which can be made.
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