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 <[email protected]> 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 <[email protected] > >wrote: > > > Thanks Marko and Brian > > > > Now I understood the complete election process > > > > > > On Fri, Feb 21, 2014 at 4:28 PM, Marko Milivojevic <[email protected] > >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 <[email protected] > >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 <[email protected]> > 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 > >>> > [email protected] > >>> > > >>> > Internetwork Expert, Inc. > >>> > http://www.INE.com <http://www.ine.com/> > >>> > >>> > > >>> > On Feb 21, 2014, at 6:01 AM, "Carlos G Mendioroz" <[email protected]> > >>> > 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 <[email protected]> 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 > _______________________________________________ Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: iPexpert on YouTube: www.youtube.com/ipexpertinc
