Re: [OSL | CCIE_RS] OSPF DR and BDR election

100 percent correct.

On Mon, Feb 24, 2014 at 1:29 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar>wrote:

> Now that everyone seems to have setled on an understanding of the
> election process, I would like to restate that there is no DR election,
> just BDR.
>
> If you follow the RFC, the only way to become DR is by having been
> elected (or autonominated) BDR first. If I'm mistaken, I would like to
> know.
>
> -Carlos
>
> Marko Milivojevic @ 23/02/2014 02:14 -0300 dixit:
> > 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&regards
> >>>>>>
> >>>>>> 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&regards
> >>>>
> >>>> 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
> >
> >
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> >
> > _______________________________________________________________________
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> >
> >
> >
> >
> >
> >
> >
>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
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Received on Mon Feb 24 2014 - 14:07:09 ART