At 11:08 AM 1/17/01, ahmad wrote:
>Hi ,
>
>I agree with priscilla , but doesnt this master/slave relationship change
>after the slave had sent its dd packets to the master then the master
>becomes slave and sents the dd packets?
It's bidirectional communication. They both send and acknowledge DD
packets, but the designation of master versus slave doesn't change. There's
no need for it to change.
I think it's kind of cool that they throw together this ad-hoc
single-purpose connection-oriented protocol to exchange their databases and
then don't use it again.
>can you send me the report of ur sniffer priscilla cause i havent yet been
Do you have a Sniffer? I use Sniffer Pro 3.0 from Network Associates. I
also use EtherPeek 4.0. Both show database description packets quite well.
If you are really a glutton for punishment, you can look at it as text here:
http://www.priscilla.com/ospfinit.html
With some work you will be able to figure out what's going on. I had two
OSPF routers [10.0.60.2] and [10.0.60.1] connected via a shared Ethernet
network. These routers were in turn connected to other networks.
Which one becomes master and why?
Note that the routers are already aware of each other's existence but have
not become fully adjacent when the trace starts. I only saved after they
had already sent hellos to each other.
Priscilla
>able to see this besides books
>Priscilla Oppenheimer <[EMAIL PROTECTED]> wrote in message
>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > I don't think the master/slave business is related to DR and BDR. It has
>to
> > do with neighbor adjacency and establishing the protocol for exchanging
>the
> > link state database.
> >
> > After initializing, two neighbors establish bidirectional communication
>and
> > then enter the ExStart state. In this state, the routers establish a
> > master/slave relationship and determine the initial database description
> > (DD) sequence number.
> >
> > At first both neighbors will claim to be the master by sending an empty DD
> > packet with the Master/Slave (MS) bit set to one. The neighbor with the
> > lower Router ID will become the slave and will reply with a DD packet in
> > which the MS bit is zero and the DD sequence number is set to the master's
> > sequence number. This DD packet is the first one with actual data, that
>is,
> > LSA summaries.
> >
> > The routers then know who is the master and who is the slave and enter the
> > Exchange state where they synchronize their link state databases.
> >
> > When I first looked at all of this on a Sniffer I was pleasantly surprised
> > to discover how complicated it is! &;-) It's a little like a TCP 3-way
> > handshake.
> >
> > Priscilla
> >
> >
> > At 02:43 PM 1/16/01, Gopinath Pulyankote wrote:
> > >Hello all,
> > > Could someone explain what is master/slave relationship during DBD
> > >exchange. My understanding is that since DR is the Router with the
>highest
> > >priority value, it will always be the master. So why have this definition
>?
> > >Or is it only used on Point-to-Point links, which don't elect DR & BDR?
> > >TIA
> > >Gopinath
> > >
> > >
> > >
> > >_________________________________
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> >
> > ________________________
> >
> > Priscilla Oppenheimer
> > http://www.priscilla.com
> >
> > _________________________________
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>
>
>_________________________________
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