Thank you for the inputs.
What I'm trying to understand is that with R3 as DR for the Segment
connecting R5-R4-R3-R1 and R1 as BDR, it's true that R1 Will promote itself
as DR, but what confuses me is the fact that R3/DR actually stayed up as far
as R4 and R5 are concerned.
I also missed the fact that between R1-R2 and R2-R3 there won't be Any
DR/BDR since these are point-to-point serial links. So in essence what BSCN
is saying is that the two DR's would actually "slug it out" to see who keeps
the DR role. As far as the two routers getting stuck in "Exstart/Exchange"
phase, I failed to mention that this happens after the Ethernet link gets
Reconnected. Like you said, this might be an IOS version issue. As a side
note, I also saw another case where after replacing A 2500 with a 4500 the
new router would not reach FULL state with A 7200 on the other end of a
point-to-point connection. I never Did hear from TAC if this was another IOS
version issue. Thanks again.
Elmer
-----Original Message-----
From: Peter van Oene [mailto:[EMAIL PROTECTED]]
Sent: Monday, September 17, 2001 10:06 PM
To: [EMAIL PROTECTED]
Subject: RE: Need clarification on BDR promotion to DR [7:20163]
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=20256&t=20163
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
