I should clarify what I wrote there though ... RSTP can detect a link failure in 6 seconds (3*hello) but the maxage timer itself is still 20 seconds by default. The 6 second failure detection and the maxage are separate things. Check out this link: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml
"On a given port, if hellos are not received three consecutive times, protocol information can be immediately aged out (or if max_age expires). " I believe it has to do with the way RSTP does things. With STP bridges basically relayed BPDUs from the root down and did not really generate many. In RSTP there is a sort of "keepalive" going on between bridges using hello BPDUs. So in Rapid, if a bridge misses 3 of those hello keepalives OR if maxage expires (the old way) it knows there is a failure. On Wed, Jul 15, 2009 at 10:35 PM, Joe Astorino <[email protected]>wrote: > I agree with you, except that the hello-time is 2 seconds by default, so in > RSTP the max-age is actually 6 seconds by default (3 missed hello BPDUs). > That was one of the major changes they made with RSTP for faster convergence > time...instead of waiting 10 hellos they changed it to 3. I remember > thinking the exact same thing when I was a student going through these. > > On Wed, Jul 15, 2009 at 6:36 PM, Martin Dimkovski <[email protected]> wrote: > >> Hi, >> >> Task 3.5 in volume 1 asks to configure switches, which are running MST, to >> "determine reachability problems within 15 seconds". The proctor guide >> suggests this to mean that the MaxAge timer needs to be set to 15 seconds. >> But doesn't MST run an RSTP (802.1w) flavor, and isn't MaxAge useless there? >> >> RSTP neighbour loss is declared after 3 missed Hellos, which would be 9 >> seconds, already below the 15 seconds. >> >> Thanks, >> Martin >> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> >> > > > -- > Regards, > > Joe Astorino - CCIE #24347 R&S > Technical Instructor - IPexpert, Inc. > Cell: +1.586.212.6107 > Fax: +1.810.454.0130 > Mailto: [email protected] > -- Regards, Joe Astorino - CCIE #24347 R&S Technical Instructor - IPexpert, Inc. Cell: +1.586.212.6107 Fax: +1.810.454.0130 Mailto: [email protected]
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