A network administrator is configuring the routers in the graphic for OSPF. The OSPF process has
been started and the networks have been configured for Area 0 as shown in the diagram. The
network administrator has several options for configuring RouterB to ensure that it will be preferred
as the designated router (DR) for the 172.16.1.0 /24 LAN segment. What configuration tasks could
be used to establish this preference? (Choose three.)
A.
Configure the priority value of the Fa0/0 interface of RouterB to a higher value than any other
interface on the Ethernet network.
B.
Change the router id of Router B by assigning the IP address 172.16.1.130/24 to the Fa0/0
interface of RouterB.
C.
Change the priority values of the Fa0/0 interfaces of RouterA and RouterC to zero.
D.
Configure a loopback interface on RouterB with an IP address higher than any IP address on
the other routers.
E.
No further configuration is necessary.
F.
Change the priority value of the Fa0/0 interface of RouterB to zero.
Explanation:
In order to ensure that a router will become the OSPF DR for any given segment, there are a
number of options. One way is to manually configure the interface priority as described in option A
above using the “ip ospf priority” interface configuration command. The second method is
described in option C. OSPF routers will always use the loopback interface IP address as the
router ID, when configured, and the router with the highest IP address will be chosen as the DR
when the priorities are the same. The final method is to change the priority of the other routers in
the segment to zero. When the OSPF priority is set to 0, the router is ineligible to become the DR
or the BDR. Important Note: The OSPF DR/BDR election process is not pre-emptive, so any
changes to the network regarding the DR/BDR election process will only occur when the routers
are restarted.