If that is the case then you are dealing with code issues. As Chuck
points out, in this scenario, both routers will either promote
themselves to DR while alone, or both will see the link as inactive (no
keepalives) In either case, reintroduction to the segment will stimulate
a new DR election. I can't see how this could be any more logical.
What do you find illogical. Also, I'm not sure what role R2 plays in
this scenario?
Pete
On 17 Sep 2001 11:04:38 -0400, Elmer Deloso wrote:
> I understand this principle, but there is no logic with the scenario
> On convergence as outlined in BSCN as follows....
>
> R2
> R5 ---- R4 ---- R3 ------------R1
>
> Here, R2 has serial links to R1 and R3. Let's say R3=DR and R1=BDR.
> BSCN states that if the Ethernet link is disconnected between
> R1 and R3, then R1 would sense that the DR went "down" and proceed
> To promoting itself as the new DR.
> I must admit I haven't tested this exact scenario yet, but I've seen
> Similar cases where the two routers in question would get stuck in
> Exstart/Exchange forever, and this particular behavior I've succeeded
> In reproducing on a test lab.
>
> Elmer
>
>
>
> -----Original Message-----
> From: Peter Van Oene [mailto:[EMAIL PROTECTED]]
> Sent: Monday, September 17, 2001 9:42 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Need clarification on BDR promotion to DR [7:20163]
>
> So far as the multiaccess segment is concerned, when you remove the DR from
> the segment, the DR is down. The only way a DR can do its job is if it has
> access to the segment in question. In this case, promoting the BDR makes
> sense since the BDR is the only other router on the segment which has
> adjacencies with all other routers and has sufficient information on where
> the DR left off to be able to take over quickly. When the old DR comes
> back, it will not become the BDR unless it is the only other router
eligible
> on the segment since a BDR election would have already taken place to
> replace the promoted BDR.
>
> Does that help?
>
> Pete
>
> *********** REPLY SEPARATOR ***********
>
> On 9/17/2001 at 8:55 AM Elmer Deloso wrote:
>
> >Hi, all.
> >I'm trying to understand the PURPOSE and LOGIC behind OSPF BDR
> >Promotion to DR. Let's say R1 is DR and R2 is BDR connected via Ethernet
> >Link. If I disconnect the cable, this would mean the BDR will promote
> >itself
> >To DR status, even though the DR never went "down". So when I reconnect
the
> >Link the DR will just "abdicate" the role? I just don't see the logic
here.
> >So now the DR will become the BDR, and if we repeat the process of
> >disconnecting
> >The link, the original scenario is restored. I've read OSPF on CCO and
> >Doyle
> >but
> >Have not come across the explanation of why OSPF was designed to behave
> >this
> >Way. Any enlightenment on this is welcome.
> >
> >Elmer
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=20230&t=20163
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