What is a reason for an OSPF router to display a designated router ID of 0.0.0.0?
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A. B. C. D.C
The correct answer is D, "The interface type is broadcast."
OSPF uses a designated router (DR) and backup designated router (BDR) to reduce the amount of traffic generated by OSPF updates. The DR and BDR are elected for each broadcast network segment, and they are responsible for forwarding OSPF updates to other routers on the same segment. In contrast, point-to-point networks, such as point-to-point leased lines or tunnels, do not require a DR and BDR, as there are only two routers on the segment.
When a router interface is configured as a broadcast network segment, it sends a Hello packet to discover other routers on the same segment. The Hello packet contains information such as the router's OSPF router ID, the subnet mask, and the router priority. If the router does not receive a Hello packet from any other router on the same segment within a certain interval, it becomes the DR. If there is already a DR on the segment, the router with the highest priority becomes the BDR.
If a router's interface is configured as a broadcast network segment but it does not receive a Hello packet from any other router on the same segment, it may display a DR ID of 0.0.0.0. This occurs because the router has not yet discovered any other routers on the same segment and has not been elected as the DR or BDR. Once the router receives a Hello packet from another router on the same segment, it will participate in the DR/BDR election process and either become the DR or BDR, or remain a regular router.
In summary, the reason for an OSPF router to display a DR ID of 0.0.0.0 is that the interface type is configured as a broadcast network segment, but the router has not yet discovered any other routers on the same segment and has not been elected as the DR or BDR.