Yup, correct. Much more interesting is to observe what happens with the
state machine on those spokes that were, form hub's perspective, DR and BDR
:-). Look at that one.
And as Brian said - this is a broken setup, but it's an interesting to
observe the process and understand WHY. And to add to Brian's list of
places where this may be relevant today: PVLAN.
-- Marko Milivojevic - CCIE #18427 (SP R&S) Senior CCIE Instructor / Managing Partner - iPexpert :: Free Video Training: http://youtube.com/iPexpertInc :: Social: http://twitter.com/@icemarkom | http://fb.me/ccie18427 :: iPexpert: http://www.ipexpert.com/Communities | +1-810-326-1444 On Sat, Feb 22, 2014 at 8:56 AM, Tony Singh <mothafungla_at_gmail.com> wrote: > > Marko > > if we make the HUB priority 0 then each spoke would see the following in > the election debugs... > > Spoke 1 > *Mar 1 05:15:25.278: OSPF: Elect BDR 0.0.0.0 > *Mar 1 05:15:25.278: OSPF: Elect DR 2.2.2.2 > *Mar 1 05:15:25.278: DR: 2.2.2.2 (Id) BDR: none > > Spoke 2 > *Mar 1 05:15:26.774: OSPF: Elect BDR 0.0.0.0 > *Mar 1 05:15:26.774: OSPF: Elect DR 3.3.3.3 > *Mar 1 05:15:26.774: DR: 3.3.3.3 (Id) BDR: none > > where in fact the HUB see's > > R1#show ip ospf neighbor > > Neighbor ID Pri State Dead Time Address Interface > 2.2.2.2 200 FULL/DR 00:00:33 172.168.18.2 Serial1/0 > 3.3.3.3 100 2WAY/DROTHER 00:00:35 172.168.18.3 Serial1/0 > > > so each spoke declares themselves as DR but the HUB elects one DR in > precedence of of priority/highest router-id > > the non DR/BDR spoke from HUBS perspective goes into a EXSTART and keeps > re-transmitting his DBD packet but stays in a DOWN state > > If the HUB remains as DR or BDR then we can get full LSA LSDB replication > from each spoke in this design = NBMA ip ospf network broadcast > > Let me know if that's not right.. > > BR > > Tony > > > > On 22 February 2014 01:47, Marko Milivojevic <markom_at_ipexpert.com> wrote: > >> Things do get a bit more tricky in hub and spoke configurations when all >> routers don't see all the hellos. Try setting up hub-and-spoke making sure >> hub is NOIT the DR. See what the result will be. Now, ignore for a second >> the fact your routing will be broken, but observe DR/BDR status on the 3 >> devices. It's really entertaining! >> >> -- >> Marko Milivojevic - CCIE #18427 (SP R&S) >> Senior CCIE Instructor / Managing Partner - iPexpert >> :: Free Video Training: http://youtube.com/iPexpertInc >> :: Social: http://twitter.com/@icemarkom | http://fb.me/ccie18427 >> :: iPexpert: http://www.ipexpert.com/Communities | +1-810-326-1444 >> >> >> >> On Fri, Feb 21, 2014 at 5:41 PM, vishal bhugra <vishal.bhugra_at_gmail.com >> >wrote: >> >> > Thanks Marko and Brian >> > >> > Now I understood the complete election process >> > >> > >> > On Fri, Feb 21, 2014 at 4:28 PM, Marko Milivojevic <markom_at_ipexpert.com >> >wrote: >> > >> >> >> >> During the WAIT state (dead-interval duration), all routers will be >> >> sending hellos with DR/BDR set to 0.0.0.0. However, all routers can see >> >> each other's hellos and since noone is claiming DR/BDR they will hold >> the >> >> election - basically. each router will decide what's going to be the >> >> topology based on hellos they've observed. One that is at that time >> >> considered the best will claim DR and the second best will claim BDR. >> >> That's how they will populate the fields once they leave the WAIT >> state. >> >> >> >> -- >> >> Marko Milivojevic - CCIE #18427 (SP R&S) >> >> Senior CCIE Instructor / Managing Partner - iPexpert >> >> :: Free Video Training: http://youtube.com/iPexpertInc >> >> :: Social: http://twitter.com/@icemarkom | http://fb.me/ccie18427 >> >> :: iPexpert: http://www.ipexpert.com/Communities | +1-810-326-1444 >> >> >> >> >> >> >> >> On Fri, Feb 21, 2014 at 3:58 PM, vishal bhugra < >> vishal.bhugra_at_gmail.com>wrote: >> >> >> >>> Hello Brian >> >>> >> >>> Thanks for your kind answer. >> >>> >> >>> If I configure 5 routers on broadcast network, all with same priority. >> >>> They >> >>> all are new in the segment and now the election start. Now my >> questions >> >>> are:- >> >>> >> >>> 1) Do all of them put their Router ID in DR field of Hello? and >> highest >> >>> RID >> >>> will become the DR and lower one will be the BDR ? >> >>> >> >>> OR >> >>> >> >>> 2) Will some one put his router ID in BDR field ? and if yes how will >> he >> >>> decide that it has to put the RID in BDR field of Hello packet and >> not >> >>> the >> >>> DR. >> >>> >> >>> >> >>> >> >>> >> >>> On Fri, Feb 21, 2014 at 2:28 PM, Brian McGahan <bmcgahan_at_ine.com> >> wrote: >> >>> >> >>> > In general the first router to join the segment becomes DR and the >> >>> second >> >>> > router to join becomes BDR. If DR fails the BDR is promoted to DR >> and >> >>> there >> >>> > is a new election for BDR. There are some odd corner cases where >> this >> >>> wont >> >>> > happen though. >> >>> > >> >>> > When the router joins the segment it listens for WAIT timer to >> expire. >> >>> If >> >>> > during this interval it receives a hello from another router on the >> >>> > segment, it will accept the DR information in the packet and start >> to >> >>> send >> >>> > hellos. If however no one is heard during WAIT, the router elects >> >>> itself DR >> >>> > and inserts this in its own hello. >> >>> > >> >>> > This mean that if for some reason communication is broken during >> WAIT >> >>> > interval, two routers can elect themselves as both DR, in which case >> >>> there >> >>> > *will* be a preemptive election once they both hear each others >> hellos. >> >>> > >> >>> > For example this could happen if your OSPF DEAD/WAIT interval is >> lower >> >>> > than your STP Forward Delay, WAIT would expire before the router can >> >>> > receive packets and it would elect itself as DR. >> >>> > >> >>> > This is not the normal case though. For more info see >> >>> > https://tools.ietf.org/html/rfc2328#page-75 >> >>> > >> >>> > >> >>> > Brian McGahan, 4 x CCIE #8593 (R&S/SP/SC/DC), CCDE #2013::13 >> >>> > bmcgahan_at_INE.com >> >>> > >> >>> > Internetwork Expert, Inc. >> >>> > http://www.INE.com <http://www.ine.com/> >> >>> >> >>> > >> >>> > On Feb 21, 2014, at 6:01 AM, "Carlos G Mendioroz" <tron_at_huapi.ba.ar >> > >> >>> > wrote: >> >>> > >> >>> > I don't know where are you reading this, but I thought that there is >> >>> > only BDR election process. Once you are BDR, then you can jump to >> DR if >> >>> > the current DR fails. >> >>> > >> >>> > So that is why, I guess. You don't opt, you have no choice :) >> >>> > -Carlos >> >>> > >> >>> > vishal bhugra @ 20/02/2014 20:28 -0300 dixit: >> >>> > >> >>> > Hello Experts >> >>> > >> >>> > >> >>> > While going through the DR and BDR election process. I gone through >> a >> >>> line >> >>> > >> >>> > wherein during the process of election the router will segregate the >> >>> list >> >>> > >> >>> > of routers who have mentioned themselves as BDR and those who have >> >>> > >> >>> > mentioned themselves as DR. >> >>> > >> >>> > >> >>> > After segregation out of the list of BDR, the elected BDR will be >> with >> >>> the >> >>> > >> >>> > highest priority and if not then highest Router ID. >> >>> > >> >>> > >> >>> > Now my question is .. Why would a router will opt himself for BDR >> and >> >>> not >> >>> > >> >>> > for DR. Or we can say how a router will come to conclusion that it >> has >> >>> to >> >>> > >> >>> > go for be a BDR not the DR. >> >>> > >> >>> > >> >>> > >> >>> > -- >> >>> > Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina >> >>> > >> >>> > >> >>> > Blogs and organic groups at http://www.ccie.net >> >>> > >> >>> > >> _______________________________________________________________________ >> >>> > Subscription information may be found at: >> >>> > http://www.groupstudy.com/list/CCIELab.html >> >>> > >> >>> > >> >>> > >> >>> > >> >>> > >> >>> > >> >>> > >> >>> > >> >>> >> >>> >> >>> -- >> >>> Thanks®ards >> >>> >> >>> Vishal >> >>> +91 8587900305 >> >>> >> >>> Best way to predict the future ..... is to create it >> >>> _______________________________________________ >> >>> Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos >> :: >> >>> >> >>> iPexpert on YouTube: www.youtube.com/ipexpertinc >> >>> >> >> >> >> >> > >> > >> > -- >> > Thanks®ards >> > >> > Vishal >> > +91 8587900305 >> > >> > Best way to predict the future ..... is to create it >> > >> _______________________________________________ >> Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: >> >> iPexpert on YouTube: www.youtube.com/ipexpertinc Blogs and organic groups at http://www.ccie.netReceived on Sat Feb 22 2014 - 21:14:20 ART
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