MST is built using RSTP as an underlying technology so you need to treat it just like RSTP for convergence issues. RSTP and thus MST integrate the legacy backbonefast feature into their engines. Backbonefast is a legacy technology that was used in PVSTP to speed up convergence time after indirect link failures. You need to understand how that works. If you need a refresher, I included a link below on RSTP
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml#inferior So, an indirect link failure in PVSTP is not the same as an indirect link failure with RSTP/MST. The difference is that because RSTP/MST employ a backbonefast-like feature, switches do not have to wait max-age after an indirect failure. I recommend you read up on backbonefast and RSTP for clarification if you need to! HTH On Wed, Jul 22, 2009 at 9:40 PM, M Jay <[email protected]> wrote: > Thanks alot joe you have provided the enough information :) > > with option one if its the indirect failure then it will take 20 seconds > (default max-age ) + 16 seconds forward delay so total of 36 seconds > > Even If I use with MST instead of PVSTP I hope the result will remain the > same.. am I right ? > SW1 > spanning-tree MST forward-time 8 > > ------------------------------ > Date: Wed, 22 Jul 2009 21:17:01 -0400 > Subject: Re: [OSL | CCIE_RS] Spanning-tree timer > From: [email protected] > To: [email protected] > CC: [email protected] > > > Option #1 assuming the question means it will wait 16 seconds AFTER max_age > has already expired. After max_age expires it is 2x forward-delay. > > Option #2 assuming the question means it will wait 16 seconds in total. > > I suppose it depends on how you interpret "...when a port fails". My best > guess is option #1, but in the real lab if I got this,I would ask the > proctor and give him the information you just gave me so he knows that you > know what you are talking about. > > Also: > > Max-Age is still 20 seconds even with RSTP/MST (verify this by doing show > span in either of those modes). There is a subtle difference. RSTP/MST can > detect a failure in 6 seconds (3x hello-time of 2 seconds) but that is a > different function than the max age. The hello BPDUs in RSTP/MST work > differently than in traditional STP and PVSTP+ because in RSTP/MST the > hellos are used between routers on each segment as sort of a "keepalive." > > On Wed, Jul 22, 2009 at 9:08 PM, M Jay <[email protected]> wrote: > > Hi > I need help in this question: > > SW1 connected with SW2 through trunk ports, when a port fails the other > port will wait for 16 second before the interface begins forwarding. > > Possible soltuions: > > SW1 > spanning-tree VLANx forward-time 8 > > Or > > Spannin-tree VLANx forward-time 5 > spanning-tree VLANx max-age 6 > > As forward-time includes listening and learning phases (5+5= 10) do I need > to include the max-age time of 6 seconds ? Does max-age time effects in > forwarding state of interface ?? > > Please assist!!!! > > Thanks > > > > > > ------------------------------ > Windows Live™ SkyDrive™: Store, access, and share your photos. See > how.<http://windowslive.com/Online/SkyDrive?ocid=TXT_TAGLM_WL_CS_SD_photos_072009> > > _______________________________________________ > 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] > > ------------------------------ > Bing™ brings you maps, menus, and reviews organized in one place. Try it > now.<http://www.bing.com/search?q=restaurants&form=MLOGEN&publ=WLHMTAG&crea=TXT_MLOGEN_Local_Local_Restaurants_1x1> > -- 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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