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

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
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>
>
> 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
>> >
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>> >
>> >
>> >
>> >
>> >
>> >
>> >
>>
>>
>> --
>> Thanks&regards
>>
>> Vishal
>> +91 8587900305
>>
>> Best way to predict the future ..... is to create it
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>
>

-- 
Thanks&regards
Vishal
+91 8587900305
Best way to predict the future ..... is to create it
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