Solved: Maxage time when selecting root port

news2010a · ‎08-15-2009

Folks, I understand that Maxage is the time a given switch will wait to hear BDPU's before it decides to elect root port. That said, I would answer e) for the question below. The correct answer according to the book is b). I can't understand why the Maxage time in this case is on the root bridge though. If the root bridge may even be down in this scenario why not consider the Maxage at the non-root switch?

1) Assume that a non-root

802.1d switch has ceased

to receive Hello BPDus.

Which SP setting determines

how long a non-root switch

waits before trying to choose

a new Root Port?

a) Hello time setting on the root

b) Maxage timer setting on the root

c) Forwrd Delay timer setting on the Root

d) Hello timer setting on the non-root switch

e) Maxage timer setting on the non-root switch

Jon Marshall · ‎08-15-2009

Marlon

The answer is b) because the timers that are used by all switches are the root bridge timers and not the local switch timers.

So prior to the loss of the BPDUs all switches would have received BPDUs from the root bridge and used the timers that the root bridge announced. If the root bridge goes down the timers learnt from the root bridge are still used.

Jon

View solution in original post

Jon Marshall · ‎08-15-2009

Marlon

The answer is b) because the timers that are used by all switches are the root bridge timers and not the local switch timers.

So prior to the loss of the BPDUs all switches would have received BPDUs from the root bridge and used the timers that the root bridge announced. If the root bridge goes down the timers learnt from the root bridge are still used.

Jon

news2010a · ‎08-15-2009

Oh!! Thanks.