Exam 300-101 topic 2 question 503 discussion

Actual exam question from Cisco's 300-101

Question #: 503
Topic #: 2

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

Show Suggested Answer

Suggested Answer: 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 ip ospf network broadcast interface sub- command
+ Configure the neighbor 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 OSPF work 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.

by Nemanja at Feb. 13, 2020, 7:48 p.m.

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Nemanja

5 years, 4 months ago

A, B, D

upvoted 2 times

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