New answer for the edited question:
Is it ok to have the NSSA router act as the DR for the link between
the ABR and itself? Or should it only be the ABR router that is in
Area 0 that acts as the BR for the link between the NSSA router and
In such a situation, there are several possibilities:
- Everything at the default: It doesn't matter which device is the DR and which is the BDR because each router will form a full
adjacency with the other router.
- One router with the priority set to
0 (never be DR or BDR): It doesn't matter which device is the DR because each router will form a
full adjacency with the other router.
- The broadcast interfaces configured as OSPF point-to-point interfaces: There will be no DR/BDR, and each router will form a full adjacency with the other
In any scenario, each of the two routers on the network will need to form a full adjacency with the other router on the link. In such a case, it would be normal to configure the interfaces on the routers to set the OSPF network type to be point-to-point using the
ip ospf network point-to-point interface command because there is no real need for a DR/BDR.
The idea behind using a DR/BDR is for links where there are multiple OSPF routers to prevent the need for each router on the link from having to form a full adjacency with every other router on the link. That can quickly get out of hand (exponentially). By using a DR, then every router only needs to create one full adjacency with the DR (and one with a BDR, if there is a BDR, which is not a requirement). That can drastically cut back on the number of adjacencies (router resources) and OSPF control traffic required on a broadcast link.
If there are only two routers on a link, then it makes sense to set the OSPF network type to point-to-point to let them simply form full adjacencies with each other, which is going to happen in any scenario. In any of the scenarios, the router resources used for adjacencies will be the same, and eliminating the need for DR/BDR makes sense because that is one less thing for a router to do.
You can even use an OSPF point-to-point network on smaller prefixes, e.g.
/24, if there are only two OSPF router in the network.
Original answer for the original question:
Your question is moot because there will be no DR/BDR for point-to-point or point-to-multipoint links. There will be no DR in your scenario.
OSPF Design Guide
Adjacencies on Point-to-Point Interfaces
OSPF will always form an adjacency with the neighbor on the other side
of a point-to-point interface such as point-to-point serial lines.
There is no concept of DR or BDR. The state of the serial interfaces
is point to point.
An OSPF point-to-multipoint interface is defined as a numbered
point-to-point interface having one or more neighbors. This concept
takes the previously discussed point-to-point concept one step
further. Administrators do not have to worry about having multiple
subnets for each point-to-point link. The cloud is configured as one
subnet. This should work well for people who are migrating into the
point-to-point concept with no change in IP addressing on the cloud.
Also, they would not have to worry about DRs and neighbor statements.
OSPF point-to-multipoint works by exchanging additional link-state
updates that contain a number of information elements that describe
connectivity to the neighboring routers.
Below are the OSPF network types, including the Cisco extensions. Please note the multipoint links (what you ask about in the question) do not elect DR/BDR, which is what makes your question moot.
OSPF elects DR/BDR on broadcast or non-broadcast links:
Perhaps you will believe RFC 2328, OSPF Version 2 (emphasis is mine):
C.6 Point-to-MultiPoint network parameters
On Point-to-MultiPoint networks, it may be necessary to configure the
set of neighbors that are directly reachable over the
Point-to-MultiPoint network. Each neighbor is identified by its IP
address on the Point-to-MultiPoint network. Designated Routers are
not elected on Point-to-MultiPoint networks, so the Designated
Router eligibility of configured neighbors is undefined.
Alternatively, neighbors on Point-to-MultiPoint networks may be
dynamically discovered by lower-level protocols such as Inverse ARP