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New Member

forward delay time in STP

Hi all

I read that the forward delay time for listening and learning is 15 secs, is this 15 seconds each, so 30 in total, which seems more real ?

3 REPLIES
Hall of Fame Super Silver

Re: forward delay time in STP

Hello Carl,

it is 15 seconds timer used two times.

by the way for the other thread:

this 15 seconds accomodates for

7 switch hops with an hello interval of two seconds:

15 = 7*2 + 1

So in legacy 802.1D if the diameter is increased over 7 hops the timer has to be changed accordingly.

the forward timer must be greater then the time it takes a message to travel on the whole tree

Hope to help

Giuseppe

New Member

Re: forward delay time in STP

so are we talking about the listening and learning timers? if so, when you change the forward delay to 20 secs, would this be 20 for each ?

also when the bpdu is sent from the root, the other switches forward this on, so it will get forwarded every 2 secs passed on from the switch before?

also am i right in saying it is different in RSTP, as every switch generates its own BPDU ?

cheers

Carl

Hall of Fame Super Silver

Re: forward delay time in STP

Hello Carl,

your understanding is correct or at least I agree with you

Hope to help

Giuseppe

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