Refer to the exhibit.

Based on this command output, what can we conclude about R3?

A.
R3 is an ABR.

B.
R3 is not connected to the backbone.

C.
R3 has four neighbors.

D.
R3 is the DR for area 2.

Explanation:
From the output we learned that this router is getting Type 3 LSAs (Summary Net Link States) for
both Area 0 and Area 3 -> It is an ABR between Area 0 & Area 3;
From the LSA Type 1 we learn that R3 only has 1 neighbor, which is 192.168.0.4
To find the DR for an area, we need to look at the LSA Type 2 of that area. In this case we find out
116.16.35.5 is the DR for area 2, not R3.
To help you understand more clearly about the “show ip ospf database” command, we want to
explain more about the fields in the output:

+ Link IDis the OSPF Router-ID of a router in the area for LSA Type 1 & 2 but it is can be the
Router-ID or the network address for LSA Type 3, 5 & 7.+ The ADV Routeris the ID of the router
that sent the LSA (Advertising Router) into the area+ Age: The max age of the link state+ Seq#
and Checksum: these fields are used to verify link-state integrity.
For example, from the Router Link States (Area 0.0.0.0):

The first “Link ID” 172.16.1.1 is the Router-ID of the local router R3 (because it is the same as
“OSPF Router with ID”). This “Link ID” is, of course, advertised by itself so the ADV Router has the
same value.
The second “Link ID” is the Router-ID of 192.168.0.4, which is advertised by 192.168.0.4 so it is
directly connected to R3.
Notice that these 2 routers belong to Area 0.
From the Net Link States:

We learn that the “Link ID” 116.16.34.4 is advertised from the neighbor 192.168.0.4, which is
directly connected to R3. This router (116.16.34.4) also belongs to Area 0 and it is the DR of that
segment.
The Summary Net Link States gives us information about LSA Type 3 (advertised by the ABR of
area 0. Recall that ABRs generate a Type 3 LSA for each subnet in one area, and advertises each
Type 3 LSA into the other areas)

From the output we learn that the subnet 116.16.35.0 is advertised via 172.16.1.1 and four routers
(in fact, interfaces) are advertised by 192.168.0.4. Notice that these routers (interfaces) can
belong to other areas.