Chapter 8 OSPF

Question 1

OSPF uses the protocol number ___________ for its inter-router communication.

Answer 1

89

Question 2

OSPF uses ___________ packet types for inter-router communication.

Answer 2

5

Question 3

What destination addresses does OSPF use, when feasible? (Choose two.)

Answer 3

IP address 224.0.0.5

MAC address 01:00:5E:00:00:05

Question 4

True or false: OSPF is only enabled on a router interface by using the command
network ip-address wildcard-mask area area-id under the OSPF router process.

Answer 4

False

Question 5

True or false: The OSPF process ID must match for routers to establish a neighbor
adjacency.

Answer 5

False

Question 6

True or false: A default route advertised with the command default information originate
in OSPF will always appear as an OSPF inter-area route.

Answer 6

False

Question 7

True or false: The router with the highest IP address is the designated router when
using a serial point-to-point link.

Answer 7

False

Question 8

OSPF automatically assigns a link cost to an interface based on a reference bandwidth
of ___________.

Answer 8

100 Mbps

Question 9

What command is configured to prevent a router from becoming the designated router
for a network segment?

Answer 9

The interface command ip ospf priority 0

Question 10

What is the advertised network for the loopback interface with IP address
10.123.4.1/30?

Answer 10

10.123.4.1/32

Question 11

hello packets

Answer 11

hello packets
Packets that are sent out at periodic interval to detect neighbors for establishing adjacency and ensuring that neighbors are still available.

Question 12

backup designated router (BDR)

Answer 12

A backup pseudonode that maintains the network segment’s state to replace the DR in the event of its failure.

Question 13

dead interval

Answer 13

dead interval
The amount of time required for a hello packet to be received for the neighbor to be deemed healthy. Upon receipt, the value resets and decrements toward zero.

Question 14

designated router (DR)

Answer 14

Context of OSPF: A pseudonode to manage the adjacency state with other routers on the broadcast network segment. Context of PIM: A PIM-SM router that is elected in a LAN segment when multiple PIM-SM routers exist to prevent the sending of duplicate multicast traffic into the LAN or the RP.

Question 15

interface priority

Answer 15

interface priority
The reference value for an interface to determine preference for being elected as the designated router.

Question 16

passive interface

Answer 16

An interface that has been enabled with a routing protocol to advertise its associated interfaces into its RIB but that does not establish neighborship with other routers associated to that interface.

Question 17

router ID (RID)

Answer 17

A 32-bit number that uniquely identifies the router in a routing domain

Question 18

shortest path tree (SPT)

Answer 18

shortest path tree (SPT)
A router’s view of the topology to reach all destinations in the topology, where the router is the top of the tree, and all of the destinations are the branches of the tree. In the context of multicast, the SPT provides a multicast distribution tree where the source is the root of the tree and branches form a distribution tree through the network all the way down to the receivers. When this tree is built, it uses the shortest path through the network from the source to the leaves of the tree.