Scenario 52 Answers

1 Which parameter determines the router that will be selected as the DR in an OSPF network?

The router with the highest OSPF priority on a segment will become the DR for that segment. The default for the interface OSPF priority is 1. If multiple routers have the same priority, the router with the highest RID will be selected as the DR.

2 Could a router with a priority value of zero assume the role of a DR or BDR in the OSPF network shown in Figure 5-13?

No. A priority value of zero indicates an interface is not to be elected as a DR or BDR. The state of the interface with priority zero will be DROTHER.

3 How is the OSPF router ID determined on a Cisco router?

The OSPF router ID is the highest IP address on the box, or the highest loopback address, if one exists.

4 What is the role of the DR and the BDR in the OSPF network shown in Figure 5-13?

Instead of each router exchanging updates with every other router on the segment, every router will exchange the information with the DR and the BDR. The DR and the BDR will relay the information to everybody else. In mathematical terms, this cuts the information exchange from O(n x n) to O(n), where n is the number of routers on a multiaccess segment.

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