It appears that way to me. I think it takes Max Age + 2x forwarding delay.
On Thu, Mar 10, 2011 at 3:14 PM, O'Brien, Neil <[email protected]> wrote: > Hi Guys, sorry for jumping into the middle of this one but I'm curious about > this. > > So if there's an indirect link failure, do all non-portfast links have to go > through LIS and LRN again? > > > > Kind regards > > Neil > > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of marc abel > Sent: 10 March 2011 02:15 > To: [email protected] > Cc: [email protected] > Subject: Re: [OSL | CCIE_RS] Rapid Spanning Tree convergence times > > Jay thank you for that, it cleared a misconception I had. I thought portfast > only affected the port in question when it came online, as when you plugged > it in. I didn't realize that it would impact an indirect re-convergence. I > tested it and it worked just like you said, I drop one packet. > > I am doing both ether-channel and HSRP on the uplinks. I'm thinking more > about what happens if I lose one of my redundant core switches. > Also my IDF's are setup as a ring or stacked topology because I don't have > enough fiber to uplink each switch. So in a situation where I lose the middle > switch in a stack I would be relying on spanning-tree re-converging. > > One other thing I am still unclear about is that the max-age still shows 20 > seconds, in the output. Isn't it supposed to be 3 x hello? > Bah, I probably just need to re-watch the STP videos. > > Cat1#show span > > VLAN0001 > Spanning tree enabled protocol rstp > Root ID Priority 24577 > Address 5475.d029.7080 > This bridge is the root > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 24577 (priority 24576 sys-id-ext 1) > Address 5475.d029.7080 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 300 > > > > > On Wed, Mar 9, 2011 at 7:50 PM, [email protected] <[email protected]> > wrote: >> Well if yor timers are that bad for VOIP you can always use hsrp if >> you don't want to use the etherchannel option. You can tune hsrp down >> to milliseconds if you wanted to. Of course your distribution switches >> need to support an enhanced IOS image >> >> Sent from my Verizon Wireless Phone >> >> ----- Reply message ----- >> From: "Jay Taylor" <[email protected]> >> Date: Wed, Mar 9, 2011 7:57 pm >> Subject: [OSL | CCIE_RS] Rapid Spanning Tree convergence times >> To: "marc abel" <[email protected]> >> Cc: <[email protected]> >> >> >> Enable portfast on the host ports and you'll see a much quicker transition. >> Just labbed this up and with portfast enabled I lost a single ping >> during the failover. Without it enabled I lost 12. >> >> For the VoIP question - in production I'd recommend building with >> Etherchannels just so STP never needs to converge. >> >> >> On Wed, Mar 9, 2011 at 5:41 PM, marc abel <[email protected]> wrote: >> >>> I have 4 switches connected in a loop. >>> >>> Cat1-------------Cat2 >>> | | >>> | | >>> Cat3----------Cat4 >>> >>> >>> Cat 1 is the root, Cat 2 is the secondary root. All the switches are >>> set to RPVSTP and I have confirmed that show spanning-tree shows RSTP >>> as the protocol. Cat 4 shows it's interface to cat3 as it's root port >>> and the interface to Cat3 as the Alternate. I have not tuned any >>> timers. >>> >>> What should be the convergence time in this situation? >>> >>> If I run a ping from a host attached to Cat4 to a host attached to >>> Cat1 and then I shut the Cat1-Cat3 interface (on the Cat1 side) it >>> takes about 32 seconds before pings pick back up. I thought RSTP was >>> supposed to converge in about 6 seconds? >>> >>> Another question, what is the fastest recovery time we can tune down >>> to from RSTP? How do others tune this for VOIP? I know that I can get >>> sub second convergence from OSPF but not all my switches have an >>> appropriate image to run ospf. >>> >>> >>> Thanks in advance. >>> >>> Marc >>> _______________________________________________ >>> For more information regarding industry leading CCIE Lab training, >>> please visit www.ipexpert.com >>> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, >> please visit www.ipexpert.com >> >> >> >> > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
