From: Mike Kraus \(mikraus\) (mikraus@cisco.com)
Date: Wed Jun 13 2007 - 23:17:47 ART
Hello all!
I had thought you only need to worry about which router is the DR if
your devices are not fully meshed on multiple access medium or if there
is some requirement in the question stating that a particular device
should or should not be DR (or in a particular neighboring state). Is
that a correct understanding? Here is a scenario that makes me question
this logic.
Assume you have a network that looks something like this:
R1---R2----R4----R5
|
R3
*
R1, R2 & R3 connected by broadcast medium (ethernet).
*
Links between R1, R2 & R3 in area 0.
*
Link between R2 & R4 in area 2.
*
Virtual-link exists between R2 and R4 to extend area 0.
*
Link between R4 & R5 in are 3.
When I did some testing I didn't seem to have an reachability issues
regardless of which router is the DR (R1, R2, or R3), unless I
overlooked something. However, I had a similar question in a practice
scenario and it had indicated that the R2 router should be the DR, but
it didn't state why (and there was no stated requirement). Is there a
reason why R2 should be the DR here?
I certainly understand the ways of how to manipulate which router
becomes the DR (OSPF priority, then router-id), I just don't understand
if it would be necessary in this circumstance.
Thanks again for the help,
Mike
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