10-01-2008 08:38 AM - edited 03-06-2019 01:42 AM
Would this be a problem...
All routers area 0
All network types broadcast
There is FR so there are Serial links set at betworktype Non-broadcast
There is a DR for the Broadcast network type
and there is a DR for the Non-broadcast type. Thus there are 2 DRs in area 0. Is this a problem. I can get around it via making the network types Point-to-Multipoint thus no second DR is elected. But do i even have to do that?
10-01-2008 08:43 AM
Michael
You seem to assume that having multiple DR in an area is a problem. That is not the case.
DR is elected per segment (per subnet) and is not per area. So it is normal to have multiple DR in area 0 and it is not a problem at all.
HTH
Rick
10-01-2008 09:29 AM
DR is elected per segment (per subnet) and is not per area.
That one statement Cleared up everything. Thank You.
10-01-2008 08:47 AM
Hello Mike,
the DR concept is link specific: on different links L3 subnets you have different DRs.
No problem in having multiple DRs in the same area.
The DR is the OSPF router responsible to represent the multi-access segment.
What really counts is that all devices connected to the same ip subnet / multiaccess segment must agree on the ip ospf network type to avoid problems.
So you have a DR on each LAN segment and a DR on each FR link that uses main interface or a point-to-mulipoint subifs.
Serial interfaces with HDLC or PPP encapsulation and FR point-to-point subif are seen as point-to-point OSPF networks and no DR is elected
So you don't need to worry about this is normal OSPF behaviour.
Hope to help
Giuseppe
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