pg 525 forwarding port

[aneksadh]

figure 10.12 pg 525

switch C is the root bridge
f0/1 of switch A and fio/2 of switch D and gi0/1 of switch B are the root ports

i understood till here

but then why do we need to make f0/2 of switch A the designated port, this will allow it to send/receive frames from this port but we already got the best path to switch C
switch B wont send any broadcasts via link GI0/2 so the stretch between switch A and B will have no traffic at all, right ??

pls can somebody be so kind to clarify this ?

thanks
anek

[Ltat42a]

The way I looked at that, Gi0/2 on Switch B is blocked to prevent loops. A B & D all need a root port back to C, A is using the Fa link, B&D are using the Gi links because of their lower cost.

[aneksadh]

The way I looked at that, Gi0/2 on Switch B is blocked to prevent loops. A B & D all need a root port back to C, A is using the Fa link, B&D are using the Gi links because of their lower cost.


but why do we need a forwarding port on the link between switch a & b as mentioned in the book

i understand the root ports of a,b,d

rgds
anek

[Ltat42a]

I'm guessing that if any of the other links go down (between A & C, B & D, or D & C) there is still a path back to C.