I just got through labing it with three routers in a ring. It doesn't matter who's advertising, it's all about the metric. The invalid, hold and flush timers all get reset at each hello. They all run simultaneously. If a hello for the same route is heard, with an equal or better metric at any time, it is used immediately and all timers are reset. But if a hello for the same route is heard, with a worse metric, and 180 seconds has not passed, it is ignored and no timers reset. Once the 180 seconds has passed, both invalid and hold down timers expire together, the route is pulled from the routing table and a hello for the route with a worse metric will no be accepted. If such a hello is heard, all timers are reset again. If no hellos come in within 60 seconds, the flush timer expires and the route is pulled from the RIP database.
So there you have it. All timers start, run and reset simultaneously. The timers can be reset by any metric after 180 seconds. But before 180 seconds, only a hello with an equal or better metric can reset the timers. Hence, a hello with a worse metric is ignored until the invalid and hold down timers expire. The flush timer doesn't expire until 60 seconds after the other timers expire, which is 240 seconds after the last hello. The flush timer only affects the contents of the RIP database. On Tue, Jan 24, 2012 at 1:45 PM, Mills, Derek < [email protected]> wrote: > It is my understanding the timers actually all reference the same starting > point, not comulatively stacking on top of each other. > > For instance using the default timers of 30 180 180 240: > > |----------|---------|---------|----------|-----------------------| > 0 30 60 90 180 240 > Update send send send no update Rx > Rx update update update Mark invalid > Mark hold-down Flush > > > > > > DEREK > > -----Original Message----- > From: [email protected] [mailto: > [email protected]] On Behalf Of Donald Robb > Sent: Monday, January 23, 2012 1:28 AM > To: 'Bob McCouch'; 'Kim Pedersen' > Cc: [email protected]; [email protected] > Subject: Re: [OSL | CCIE_RS] Correct Understanding the RIP timers! > > Does anyone have an example case where the route *remains* in hold down for > more than 60 seconds after the invalid timer has expired? > > When the router sends out the poision route to its neighbors, it will stay > in holddown until it the router receives the poisoned route back from its > peers, it will not leave the holddown state until it does. > You can see this pretty easily if you set the holddown timer to something > like 10 seconds and watch the debugs. > > Cheers, > Donald Robb > Productive Networks / Network Consultant > ______________________________________________________________ > CCIE Written, CCIP, CCSP, CCDP, CCNP, CCNA: Voice, JNCIP, SCP, MCSA 2003, > Security+, CCSE.R65, PACE > Experts-Exchange: Guru - R&S > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Bob McCouch > Sent: January-22-12 10:05 PM > To: Kim Pedersen > Cc: [email protected]; [email protected] > Subject: Re: [OSL | CCIE_RS] Correct Understanding the RIP timers! > > I see the same. I just did this with the following: > > R1---R3---R2 (happened to match an existing .net file better for me). > > I originated 8.8.8.8/32 into RIP from R1 with an outbound offset so I > could > make the same route from R2 show up both better and worse than R1's version > of the route. I swapped offset lists on R2 to change the option it was > offering to R3, and used an outbound distribute list on R1 to block the > route from that side to simulate failure. I also altered R1's offset list > for a few tests to make the route get advertised from the original source > with same, better, and worse metrics. > > Update period is 30 seconds. > Invalid timer is 180 seconds. > Flush timer is 240 seconds. > The router indicates it's entering hold down after the invalid timer has > expired and claims it's 180 seconds of hold down. > > Here's what I'm observing: > > Will accept worse metric from alternate source during update interval: No > (obvious) > > Will accept better metric from alternate source during update interval: Yes > (obvious) > > > Will accept worse metric from alternate source during invalid interval > (between 30-180 sec): No (obvious) > > Will accept better metric from alternate source during invalid interval > (between > 30-180 sec): Yes (obvious) > > > Will accept worse metric from alternate source during holddown (btwn > 180-240 sec): No > > Will accept better metric from alternate source during holddown (btwn > 180-240 > sec): No > > Will accept worse metric from original source during holddown (btwn 180-240 > sec): No > > Will accept better metric from original source during holddown (btwn > 180-240 > sec): No > > Will accept any metric from any source after flush at approx 240 sec: YES > > > Once the invalid timer expires, the router starts sending out poisoned > updates to all neighbors. From that point unit the flush timer fires (60 > seconds later), the router will effectively accept no updates on that > route. > That includes better or worse metrics, either from alternate sources or > from > the router the "lost" route originally came from. After the flush occurs > and > the route is completely removed from the route table, the next update that > comes in for that route is accepted. So practically speaking, the holddown > time seems to be 60 seconds, not 180. > > I also tried setting the offset from R1 to 15 so the route arrived at R3 as > inaccessible (simulating a failure further upstream and the adjacent router > hitting the invalid expiration), and R3 immediately flushed the route from > the table upon hearing of the inaccessible route, and then accepted the > next > route advertisement from the alternate path. > > So it seems to me that the hold down interval is really just a short > moratorium on accepting any updates to a route from the period after it's > been declared invalid until the garbage collection comes around and flushes > the route. From a standpoint of loop prevention (with respect to counting > to > infinity) I can see that it gives a little window for everyone in the > network to agree the route is gone and flush it, and whatever path is still > being advertised at the end of that must really be an alternate route, but > I > just don't see where the 180 second claim comes from. > > Does anyone have an example case where the route *remains* in hold down for > more than 60 seconds after the invalid timer has expired? > > > > On Sun, Jan 22, 2012 at 4:49 AM, Kim Pedersen <[email protected]> wrote: > > > Hi, > > > > In my testing, when a route is in hold-down, you can't even get the > > router to accept the same route from anywhere else even though it has > > a _better_ metric. > > > > Fx.: > > > > R1 <-> R2 <-> R3 > > > > 100.100.100.100/32 is advertised from R1 to R2 with a metric of 4. > > > > I stand by on R3 to insert the 100.100.100.100/32 with a standard > > metric of 1 > > > > I then apply a distribute list on R1 toward R2, causing the route to > > go into hold-down after a while. > > > > After the hold-down occurs, i insert the 100.100.100.100/32 network on > > R3, and view the rip debug on R2. > > It will _not_ insert this route even though it has a better metric. > > > > After it goes out of hold-down, it will insert this route. > > > > > > Sincerely, > > Kim Pedersen > > > > On Jan 22, 2012, at 10:23 AM, CCIE KID wrote: > > > > > The Invalid / Holdown starts at 180 seconds .. I have a doubt in it, > > > > > > THere is a route learned from RIP and u haven't got any updates for > > > 60 seconds , then the route goes into Invalid state for 180 ( so ie > > > from the > > > 60 seconds so Invalid TImer is actually 120 seconds ) and it doesnt > > update > > > for that 180 seconds if it gets any metric with a worse metric.. And > > > it waits for another 60 seconds to flush it. > > > > > > Am i getting it right this time :) > > > > > > > > > > > > > > > > > > On Sun, Jan 22, 2012 at 2:31 PM, Donald Robb > > > <[email protected]> > > wrote: > > > > > >> It's not actually a 180 second period, the entire flush process > > >> will > > take > > >> 240 seconds.**** > > >> > > >> The invalid/holddown portion begins at 180 seconds and ends when > > >> the > > route > > >> is flushed at 240 seconds or if it is taken out of hold down.**** > > >> > > >> ** ** > > >> > > >> During the invalid/holddown 60 second period (by default) before > > >> the route is flushed the router won't believe any updates for the > > >> route > > unless > > >> it is a better metric.**** > > >> > > >> ** ** > > >> > > >> Cheers,**** > > >> > > >> Donald Robb**** > > >> > > >> Productive Networks / Network Consultant**** > > >> > > >> ______________________________________________________________**** > > >> > > >> CCIE Written, CCIP, CCSP, CCDP, CCNP, CCNA: Voice, JNCIP, SCP, MCSA > > 2003, > > >> Security+, CCSE.R65, PACE**** > > >> > > >> Experts-Exchange: Guru - R&S**** > > >> > > >> ** ** > > >> > > >> *From:* CCIE KID [mailto:[email protected]] > > >> *Sent:* January-22-12 1:35 AM > > >> *To:* Donald Robb > > >> *Cc:* Matthew P. Smith; [email protected]; > > >> [email protected] > > >> > > >> *Subject:* Re: [OSL | CCIE_RS] Correct Understanding the RIP > > >> timers!**** > > >> > > >> ** ** > > >> > > >> Donald, > > >> > > >> I got ur point man. So RIP wont accept any routes which are the > > >> worser metric than anyone..in the 180 sec period ... After 180 > > >> seconds if it > > again > > >> gets the worse update, it would update it. > > >> > > >> In that 180 second, all the stale information woul get flushed out > > >> in > > that > > >> time. so after that 180 sec it wont get that particular update and > > correct > > >> information will be passed. > > >> > > >> **** > > >> > > >> On Sun, Jan 22, 2012 at 1:39 PM, Donald Robb > > >> <[email protected]> > > >> wrote:**** > > >> > > >> The holddown timer is more or less a sanity check to the invalid > > >> timer, > > it > > >> guards against the router learning the same route from another > > >> update > > that > > >> has same or worse metric so the features complement each other. > > >> If you think about it that way, it make sense that would run at the > > >> same time as the invalid period. > > >> > > >> Hope that helps clear things up**** > > >> > > >> > > >> Cheers, > > >> Donald Robb > > >> Productive Networks / Network Consultant > > >> ______________________________________________________________ > > >> CCIE Written, CCIP, CCSP, CCDP, CCNP, CCNA: Voice, JNCIP, SCP, MCSA > > 2003, > > >> Security+, CCSE.R65, PACE > > >> Experts-Exchange: Guru - R&S > > >> > > >> -----Original Message----- > > >> From: [email protected]**** > > >> > > >> [mailto:[email protected]] On Behalf Of CCIE KID > > >> Sent: January-22-12 12:51 AM > > >> To: Matthew P. Smith > > >> Cc: [email protected]; > > >> [email protected] > > >> Subject: Re: [OSL | CCIE_RS] Correct Understanding the RIP timers! > > >> > > >> Hi > > >> > > >> > > >> Both the Holdown and Invalid run parallely. As far as i understood > > >> the logic. > > >> > > >> In Invalid Time period, if there is any other update for the same > > >> route > > is > > >> updated ( The metric can be worse or same ) can be updated > > >> > > >> But in Hold Time period, If there is any other worse update or the > > >> same metric update reaches, it would discard it, > > >> > > >> So my question is how can these two timers can run parallely, How > > >> can > > thsi > > >> solves the purpose > > >> > > >> Because both the timers have contrasting software feature, Because > > >> the trigger is different, > > >> > > >> In Invalid the trigger is to update even the worst metric, But in > > >> Hold > > Time > > >> the trigger is not to update the worst metric, > > >> > > >> How this can be parallel. Is there any demarcation point for this.. > > >> > > >> I may be wrong. > > >> Can any expert correct me. > > >> > > >> On Sun, Jan 22, 2012 at 3:02 AM, Matthew P. Smith > > >> <[email protected]>wrote: > > >> > > >>> Though debugs are good, you can test this just by shutting down > > >>> the interface while watching the clock. > > >>> > > >>> When I did this, the route got pulled from the routing table 3 > > >>> minutes after the last hello(invalid timer). > > >>> > > >>> The route got pulled from the rip database after another 60 > > >>> seconds(flush timer). Keep in mind that according to Cisco, the > > >>> flush timer is 4 minutes, not 60 seconds) > > >>> > > >>> The hold down timer lasts for 3 minutes and begins after the route > > >>> goes invalid. If an advertisement for the invalid route is heard > > >>> before the hold down timer expires, it will be ignored under > > >>> certain > > >> circumstances. > > >>> > > >>> BUT I'm not 100% sure if this works. Will an update identified by > > >>> the hold down timer update the flush timer? Or what if the update > > >>> comes in through a different interface or from a different router > > >>> ID. Would the advertisement still be subject to the flush and/or hold > down timers? > > >>> > > >>> I guess I need to lab this out again. > > >>> But this time from different router IDs and incoming interfaces. > > >>> And before and after the flush timer expires. > > >>> Only 4 more tests to put this to bed :) > > >>> > > >>> On Jan 20, 2012, at 5:58 PM, Bob McCouch <[email protected]> wrote: > > >>> > > >>>> The output from my lab below was from 'debug ip rip database' and > > >>>> 'debug ip routing'. > > >>>> > > >>>> Bob > > >>>> -- > > >>>> Sent from my iPhone, please excuse any typos. > > >>>> > > >>>> On Jan 20, 2012, at 1:15 PM, "[email protected]" > > >>>> <[email protected]> wrote: > > >>>> > > >>>>> Hello > > >>>>> > > >>>>> What is the output of debup ip rip ? > > >>>>> -----Original Message----- > > >>>>> From: Rostam Sohrab <[email protected]> > > >>>>> Sender: [email protected] > > >>>>> Date: Fri, 20 Jan 2012 09:31:35 > > >>>>> To: Bob McCouch<[email protected]> > > >>>>> Cc: [email protected]<[email protected]> > > >>>>> Subject: Re: [OSL | CCIE_RS] Correct Understanding the RIP timers! > > >>>>> > > >>>>> Thanks to Bob & Donald! > > >>>>> > > >>>>> Those were certainly superb explanations making the > > >>>>> understanding > > >>> pretty clear for me! > > >>>>> > > >>>>> -RS > > >>>>> > > >>>>> > > >>>>> ________________________________ > > >>>>> From: Bob McCouch <[email protected]> > > >>>>> To: Rostam Sohrab <[email protected]> > > >>>>> Cc: "[email protected]" <[email protected]> > > >>>>> Sent: Friday, 20 January 2012 8:51 AM > > >>>>> Subject: Re: [OSL | CCIE_RS] Correct Understanding the RIP timers! > > >>>>> > > >>>>> > > >>>>> Best way to see this is to lab it up. I set up a very simple > > >>>>> network > > >>> with R1 and R2 connected via ethernet. I advertised a loopback > > >>> from R2 into RIP, and then on R2 set the ethernet interface > > >>> passive to stop routing updates without giving IOS any hints by > > >>> dropping the interface. Here's what > > >>> happened: > > >>>>> > > >>>>> R1#sh ip ro | b Gate > > >>>>> Gateway of last resort is not set > > >>>>> > > >>>>> 10.0.0.0/24 is subnetted, 2 subnets > > >>>>> R 10.1.0.0 [120/1] via 10.1.124.2, 00:00:12, FastEthernet0/0 > > >>>>> C 10.1.124.0 is directly connected, FastEthernet0/0 > > >>>>> > > >>>>> R1#sh clock > > >>>>> 22:03:17.475 UTC Wed Jan 19 2011 R1#!This is when I set Fa0/0 > > >>>>> passive on R2 > > >>>>> > > >>>>> R1# > > >>>>> Jan 19 22:05:56.975: RIP-DB: invalidated route of 10.1.0.0/24 > > >>>>> via > > >>> 10.1.124.2 > > >>>>> Jan 19 22:05:56.979: RT: delete route to 10.1.0.0 via > > >>>>> 10.1.124.2, rip > > >>> metric [120/1] > > >>>>> Jan 19 22:05:56.979: RT: no routes to 10.1.0.0, entering > > >>>>> holddown Jan 19 22:05:56.987: RIP-DB: Remove 10.1.0.0/24, > > >>>>> (metric > > >>>>> 4294967295) > > >>> via 10.1.124.2, FastEthernet0/0 > > >>>>> > > >>>>> R1#sh ip ro | b Gate > > >>>>> Gateway of last resort is not set > > >>>>> > > >>>>> 10.0.0.0/24 is subnetted, 2 subnets > > >>>>> R 10.1.0.0/24 is possibly down, > > >>>>> routing via 10.1.124.2, FastEthernet0/0 > > >>>>> C 10.1.124.0 is directly connected, FastEthernet0/0 > > >>>>> > > >>>>> R1# > > >>>>> Jan 19 22:06:56.991: RIP-DB: garbage collect 10.1.0.0/24 Jan 19 > > >>>>> 22:06:56.995: RT: delete subnet route to 10.1.0.0/24 > > >>>>> > > >>>>> R1#sh ip ro | b Gate > > >>>>> Gateway of last resort is not set > > >>>>> > > >>>>> 10.0.0.0/24 is subnetted, 1 subnets > > >>>>> C 10.1.124.0 is directly connected, FastEthernet0/0 > > >>>>> > > >>>>> > > >>>>> So 3 minutes after the last received update, the route was > > >>>>> marked > > >>> invalid, and 60 seconds after that the route was flushed. So all > > >>> timers are running concurrently, the update timer, the > > >>> invalid/holddown timers, and the flush timer. > > >>>>> > > >>>>> > > >>>>> Bob > > >>>>> > > >>>>> > > >>>>> On Thu, Jan 19, 2012 at 6:56 AM, Rostam Sohrab > > >>>>> <[email protected]> > > >>> wrote: > > >>>>> > > >>>>> > > >>>>>> > > >>>>>> I have a little confusion in the understanding of RIP timers. > > >>>>>> > > >>>>>> First the basics... > > >>>>>> > > >>>>>> update timer is 30 secs --> Invalid timers should be 3 times of > > >>>>>> update > > >>> i.e 90secs but the default is 180secs --> Holddown timers should > > >>> be 3 times of update i.e, 90secs but the default is 180secs --> > > >>> Flush timer, default is 240 secs. > > >>>>>> > > >>>>>> Now there are three parts to my question... > > >>>>>> > > >>>>>> The first question might sound silly but for the sake of a > > >>>>>> clear > > >>> understanding I'll write it. > > >>>>>> > > >>>>>> > > >>>>>> 1. Does the RIP updates timers work is series? i.e after one > > >>>>>> elapses > > >>> the other starts? > > >>>>>> > > >>>>>> ex: once U-30sec is over --> Invalid starts and runs for 180 > > >>>>>> secs > > >>>>>> --> > > >>> Holddown starts and runs for another 180secs --> And finally flush > > >>> timer starts and runs for 240secs. > > >>>>>> > > >>>>>> Here the total time would be 30+180+180+240=630secs until a > > >>>>>> route is > > >>> flushed out which is looking quite unreasonable! > > >>>>>> > > >>>>>> 2. Does the Invalid, Holddown & flush timers work is parallel? > > >>>>>> > > >>>>>> ex: once U-30sec is over -> Invalid, Holddown runs for 180secs > > >>>>>> along > > >>> with the flushtimer which runs for 240secs? > > >>>>>> > > >>>>>> Here the total time would be 30+240=270secs until a route is > > >>>>>> flushed > > >>> out which looks very much acceptable. > > >>>>>> > > >>>>>> > > >>>>>> 3. And why does the Invalid & Holddown timers run in parallel, > > >>>>>> if all > > >>> they do? > > >>>>>> > > >>>>>> Because at the end of these two timers (IT & HDT) it would take > > >>> another 60secs for flush timer to flush out the route, which means > > >>> that all the timers IT/HDT/FT are kicking off at the same time > > >>> immediately after update timer expires! > > >>>>>> > > >>>>>> I think I'm just complicating what is supposed to be a simple > > >>> understanding!!! > > >>>>>> > > >>>>>> -RS > > >>>>>> _______________________________________________ > > >>>>>> For more information regarding industry leading CCIE Lab > > >>>>>> training, > > >>> please visit www.ipexpert.com > > >>>>>> > > >>>>>> Are you a CCNP or CCIE and looking for a job? Check out > > >>> www.PlatinumPlacement.com > > >>>>>> > > >>>>>> http://onlinestudylist.com/mailman/listinfo/ccie_rs > > >>>>>> > > >>>>> _______________________________________________ > > >>>>> For more information regarding industry leading CCIE Lab > > >>>>> training, > > >>> please visit www.ipexpert.com > > >>>>> > > >>>>> Are you a CCNP or CCIE and looking for a job? Check out > > >>> www.PlatinumPlacement.com > > >>>>> > > >>>>> http://onlinestudylist.com/mailman/listinfo/ccie_rs > > >>>> _______________________________________________ > > >>>> For more information regarding industry leading CCIE Lab > > >>>> training, > > >>> please visit www.ipexpert.com > > >>>> > > >>>> Are you a CCNP or CCIE and looking for a job? Check out > > >>> www.PlatinumPlacement.com > > >>>> > > >>>> http://onlinestudylist.com/mailman/listinfo/ccie_rs > > >>> _______________________________________________ > > >>> For more information regarding industry leading CCIE Lab training, > > >>> please visit www.ipexpert.com > > >>> > > >>> Are you a CCNP or CCIE and looking for a job? Check out > > >>> www.PlatinumPlacement.com > > >>> > > >>> http://onlinestudylist.com/mailman/listinfo/ccie_rs > > >>> > > >> > > >> > > >> > > >> -- > > >> With Warmest Regards, > > >> > > >> CCIE KID > > >> CCIE#29992 (Security) > > >> _______________________________________________ > > >> For more information regarding industry leading CCIE Lab training, > > please > > >> visit www.ipexpert.com > > >> > > >> Are you a CCNP or CCIE and looking for a job? Check out > > >> www.PlatinumPlacement.com > > >> > > >> http://onlinestudylist.com/mailman/listinfo/ccie_rs**** > > >> > > >> > > >> > > >> > > >> -- > > >> With Warmest Regards, > > >> > > >> CCIE KID > > >> CCIE#29992 (Security) > > >> > > >> **** > > >> > > > > > > > > > > > > -- > > > With Warmest Regards, > > > > > > CCIE KID > > > CCIE#29992 (Security) > > > _______________________________________________ > > > For more information regarding industry leading CCIE Lab training, > > please visit www.ipexpert.com > > > > > > Are you a CCNP or CCIE and looking for a job? Check out > > www.PlatinumPlacement.com > > > > > > http://onlinestudylist.com/mailman/listinfo/ccie_rs > > > > > > > > // Freedom Matters > > CCIE #29189 > > http://www.packet-forwarding.net > > > > > > > > _______________________________________________ > > For more information regarding industry leading CCIE Lab training, > > please visit www.ipexpert.com > > > > Are you a CCNP or CCIE and looking for a job? Check out > > www.PlatinumPlacement.com > > > > http://onlinestudylist.com/mailman/listinfo/ccie_rs > > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > http://onlinestudylist.com/mailman/listinfo/ccie_rs > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > http://onlinestudylist.com/mailman/listinfo/ccie_rs > > > ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > Anheuser-Busch InBev Email Disclaimer www.ab-inbev.com > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > http://onlinestudylist.com/mailman/listinfo/ccie_rs > -- Matthew P. Smith [email protected] _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? 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