Refer to the exhibit. Two routers are connected by Frame Relay and are running OSPF
between them. Each router has been configured with the appropriate network statements
under router ospf 1, but the routers are not forming an adjacency.
Which of the following three commands could be configured on each router to correct this
problem? (Choose three.)
A.
RouterC(config-if)#ip ospf network broadcast
RouterD(config-if)#ip ospf network broadcast
B.
RouterC(config-if)#ip ospf network point-to-point
RouterD(config-if)#ip ospf network point-to-point
C.
RouterC(config-router)#neighbor 10.100.100.4
RouterD(config-router)#neighbor 10.100.100.3
D.
RouterC(config-router)#neighbor 10.255.255.254
RouterD(config-router)#neighbor 10.255.255.253
Explanation:
By default, Frame Relay is classified as a non-broadcast network, meaning it doesn’t send
any broadcasts/multicasts like RIP, OSPF or EIGRP updates across the network (hello
packets of OSPF are multicast to 224.0.0.5). Hence,in NBMA network, the neighbors are
not discovered automatically; they must be configured manually. There are two ways to
simulate a broadcast model on an NBMA network:
+ Define the network type as broadcast with the “ipospf network broadcast” interface subcommand
+ Configure the neighbor <neighbor-ip-address> statements under router ospf mode
(though configuring the neighbor statement on one end is sufficient to form adjacency, it is a
good practice to have it configured on both the ends)
Besides these two ways, another way for making OSPFwork with Frame Relay is
configuring the network as a Point-to-Point network(or Point-to-Multipoint, notice that OSPF
treats Point-to-Multipoint network as a collective of point-to-point links).
Some information about Point-to-Multipoint (or Point-to-Point) network:
Note: Point-to-Multipoint networks do not maintain a DR/BDR relationship.