OSPF Review Questions

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6. Write the command that will enable OSPF process 101 on a router.

6. router ospf 101

7. Write the command that will display details of all OSPF routing processes enabled on a router.

7. show ip ospf

8. Write the command that will display interface-specific OSPF information.

8. show ip ospf interface

9. Write the command that will display all OSPF neighbors.

9. show ip ospf neighbor

10. Write the command that will display all different OSPF route types that are currently
known by the router.

10. show ip ospf database

3. Which of the following describe the process identifier that is used to run OSPF on a router?
(Choose two.)
A. It is locally significant.
B. It is globally significant.
C. It is needed to identify a unique instance of an OSPF database.
D. It is an optional parameter required only if multiple OSPF processes are running on
the router.
E. All routes in the same OSPF area must have the same Process ID if they are to exchange
routing information.

3. A, C. The Process ID for OSPF on a router is only locally significant and you can use the
same number on each router, or each router can have a different number—it just doesn't
matter. The numbers you can use are from 1 to 65,535. Don't get this confused with area
numbers, which can be from 0 to 4.2 billion.

6. You get a call from a network administrator who tells you that he typed the following into
his router:
Router(config)#router ospf 1
Router(config-router)#network 10.0.0.0 255.0.0.0 area 0
He tells you he still can't see any routes in the routing table. What configuration error did the
administrator make?
A. The wildcard mask is incorrect.
B. The OSPF area is wrong.
C. The OSPF Process ID is incorrect.
D. The AS configuration is wrong.

6. A. The administrator typed in the wrong wildcard mask configuration. The wildcard should
have been 0.0.0.255

7. Which of the following protocols support VLSM, summarization, and discontiguous networking?
(Choose three.)
A. RIPv1
B. IGRP
C. EIGRP
D. OSPF
E. BGP
F. RIPv2

7. C, D, F. RIPv1 and IGRP are true distance-vector routing protocols and can't do much,
really—except build and maintain routing tables and use a lot of bandwidth! RIPv2, EIGRP,
and OSPF build and maintain routing tables, but they also provide classless routing, which
allows for VLSM, summarization, and discontiguous networking.

8. Which of the following are true regarding OSPF areas? (Choose three.)
A. You must have separate loopback interfaces configured in each area.
B. The numbers you can assign an area go up to 65,535.
C. The backbone area is also called area 0.
D. If your design is hierarchical, then you don't need multiple areas.
E. All areas must connect to area 0.
F. If you have only one area, it must be called area 1.

8. C, D, E. Loopback interfaces are created on a router, and the highest IP address on a loopback
(logical) interface becomes the RID of the router but has nothing to do with areas and is optional,
so option A is wrong. The numbers you can create an area with are from 0 to 4,294,967,295—
option B is wrong. The backbone area is called area 0, so option C is correct. All areas must connect
to area 0, so option E is correct. If you have only one area, it must be called area 0, so option
F is incorrect. This leaves option D, which must be correct; it doesn't make much sense, but it is
the best answer.

10. A network administrator needs to configure a router with a distance-vector protocol that
allows classless routing. Which of the following satisfies those requirements?
A. IGRP
B. OSPF
C. RIPv1
D. EIGRP
E. IS-IS

10. D. In this question, we're calling EIGRP just plain old distance vector. EIGRP is an "advanced"
distance-vector routing protocol, sometimes called a hybrid routing protocol because it uses the
characteristics of both distance-vector and link-state routing protocols.

12. For some reason, you cannot establish an adjacency relationship on a common Ethernet link
between two routers. Looking at the output below, what is the cause of the problem?
RouterA#
Ethernet0/0 is up, line protocol is up
Internet Address 172.16.1.2/16, Area 0
Process ID 2, Router ID 172.126.1.1, Network Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 172.16.1.2, interface address 172.16.1.1
No backup designated router on this network
Timer intervals configured, Hello 5, Dead 20, Wait 20, Retransmit 5
RouterB#
Ethernet0/0 is up, line protocol is up
Internet Address 172.16.1.1/16, Area 0
Process ID 2, Router ID 172.126.1.1, Network Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 172.16.1.1, interface address 172.16.1.2
No backup designated router on this network
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
A. The OSPF area is not configured properly.
B. The priority on RouterA should be set higher.
C. The cost on RouterA should be set higher.
D. The Hello and Dead timers are not configured properly.
E. A backup designated router needs to be added to the network.
F. The OSPF Process ID numbers must match.

12. D. The Hello and Dead timers must be set the same on two routers on the same link or they
will not form an adjacency (relationship). The default timers for OSPF are 10 seconds for the
Hello timer and 40 seconds for the Dead timer.

14. Which type of OSPF network will elect a backup designated router? (Choose two.)
A. Broadcast multi-access
B. Non-broadcast multi-access
C. Point-to-point
D. Broadcast multipoint

14. A, B. DR and BDR are elected on broadcast and non-broadcast multi-access networks. Frame
Relay is a non-broadcast multi-access (NBMA) network by default. No DR is assigned on any
type of point-to-point link. No DR/BDR is assigned on the NBMA point-to-multipoint due to
the hub/spoke topology.

15. Which two of the following commands will place network 10.2.3.0/24 into area 0? (Choose two.)
A. router eigrp 10
B. router ospf 10
C. router rip
D. network 10.0.0.0
E. network 10.2.3.0 255.255.255.0 area 0
F. network 10.2.3.0 0.0.0.255 area0
G. network 10.2.3.0 0.0.0.255 area 0

15. B, G. To enable OSPF, you must first start OSPF using a Process ID. The number is irrelevant;
just choose a number from 1 to 65,535 and you're good to go. After you start the OSPF process,
you must configure any network that you want advertised via OSPF using wildcards and
the area command. Answer F is wrong because there must be a space after the parameter area
and before you list the area number.

17. What are three reasons for creating OSPF in a hierarchical design? (Choose three.)
A. To decrease routing overhead
B. To speed up convergence
C. To confine network instability to single areas of the network
D. To make configuring OSPF easier

17. A, B, C. OSPF is created in a hierarchical design, not a flat design like RIP. This decreases
routing overhead, speeds up convergence, and confines network instability to a single area
of the network.

18. What is the administrative distance of OSPF?
A. 90
B. 100
C. 110
D. 120

18. C. The administrative distance (AD) is a very important parameter in a routing protocol. The lower
the AD, the more trusted the route. If you have IGRP and OSPF running, by default IGRP routes
would be placed in the routing table because IGRP has a lower AD of 100. OSPF has an AD of 110.
RIPv1 and RIPv2 both have an AD of 120, and EIGRP is the lowest, at 90.

20. If routers in a single area are configured with the same priority value, what value does a router
use for the OSPF Router ID in the absence of a loopback interface?
A. The lowest IP address of any physical interface
B. The highest IP address of any physical interface
C. The lowest IP address of any logical interface
D. The highest IP address of any logical interface

20. B. At the moment of OSPF process startup, the highest IP address on any active interface will
be the Router ID (RID) of the router. If you have a loopback interface configured (logical
interface), then that will override the interface IP address and become the RID of the router
automatically.

QUESTION NO: 237
A router receives information about network 192.168.10.0/24 from multiple sources. What will the
router consider the most reliable information about the path to that network?
A. a static route to network 192.168.10.0/24 with a local serial interface configured as the next hop
B. a default route with a next hop address of 192.168.10.1
C. a static route to network 192.168.10.0/24
D. a RIP update for network 192.168.10.0/24
E. an OSPF update for network 192.168.0.0/16
F. a directly connected interface with an address of 192.168.10.254/24

Answer: F
Explanation:
Administrative distance refers to the reliability of one routing protocol. Each routing protocol is
specified a reliability level from high to low depending on the administrative distance. For the
routing information of two different routing protocols to the same destination, the router will make
decision on the basis of the administrative distance.

QUESTION NO: 300
A routing protocol is required that supports:
1) routing update authentication
2) an addressing scheme that conserves IP addresses
3) multiple vendors
4) a network with over 50 routers
Which routing protocol fulfills these requirements?
A. RIPv2
B. RIPv1
C. OSPF
D. EIGRP

Answer: C
Explanation:
EIGRP is CISCO private agreement, which will not support non-CISCO devices; RIPv1 and RIPv2
are distance vector protocol, supporting up to 15 hop, and 16 hop is inaccessible. RIPv1 does not
support routing update verification. Although the convergence rate of OSPF is slower than EIGRP,
but OSPF has better expansibility. And OSPF supports multi-vendor devices, and is applicable to
large networks.

QUESTION NO: 304
A router learns about a remote network from EIGRP, OSPF, and a static route. Assuming all
routing protocols are using their default administrative distance, which route will the router use to
forward data to the remote network?
A. The router will use the static route.
B. The router will use the OSPF route.
C. The router will load balance and use all three routes.
D. The router will use the EIGRP route.

Answer: A
Explanation:
When a router learns about the same network via multiple sources, the router will choose the
source with the lowest administrative distance (AD). By default, the AD for these routing protocols
are:
Connected Interface has 0 AD
Static Route : 1
EIGRP : 90
OSPF : 110
So, the static route will be chosen since it has the lowest AD.

QUESTION NO: 306
When designing OSPF networks; what is the purpose of using a hierarchical design?(Choose
three)
A. To reduce the complexity of router configuration
B. To confine network instability to single areas of the network
C. To reduce routing overhead
D. To speed up convergence

Answer: B,C,D
Explanation:
The reason for regional structure division in OSPF network is: In a small network, the structure of
router is not complicated, it is easy to identify routes to different destinations. However, in large
networks, the link structure is complex, the number of the potential paths for different destinations
is large. Therefore, the SPF algorithm which compares all possible routes is very complex and
requires a very long time.
Link State Routing Protocol often divides network into area structures to reduce the amount of
SPF algorithm. The number of routers within the area and diffusing LSA is less, which means that
the link-state database is small. The result is that the amount of SPF algorithm is smaller and the
time needed is shorter .
An OSPF network designed in a hierarchical fashion with different areas is used because a small
change in the topology of a single area won't force every router to run the SPF algorithm.
Changes in one area are limited to that area only, not to every router within the entire network.
Confining the topology changes to one area reduces the overhead and speeds the convergence of
the network.
Reference: CCNA Self-Study CCNA ICND exam certification Guide (Cisco Press, ISBN 1-58720-
083-X) Page 194
Incorrect Answers:
A: This choice is incorrect because a hierarchical design actually adds complexity to the router
configuration.

QUESTION NO: 308
A router has learned three possible routes that could be used to reach a destination network. One
route is from EIGRP and has a composite metr of 20514560. Another route is from OSPF with a
metric of 782. The last is from RIPv2 and has a metric of 4. Which route or routes will the router
install in the routing table?
A. the OSPF route
B. the EIGRP route
C. the RIPv2 route
D. all three routes
E. the OSPF and RIPv2 routes

Answer: B

QUESTION NO: 313
Which routing protocol by default uses bandwidth and delay as metrics?
A. EIGRP
B. RIP
C. BGP
D. OSPF

Answer: A
Explanation:
This question tests the metrics of various routing protocols.
RIP uses hop-count as metrics; BGP uses complicated path attributes as metrics; OSPF uses
bandwidth as metrics; and EIGRP uses bandwidth and delay as metrics by default.

QUESTION NO: 315
Which routing protocols will support the following IP addressing scheme? (Choose three.)
Network 1 - 192.168.10.0 /26
Network 2 - 192.168.10.64 /27
Network 3 - 192.168.10.96 /27
Network 4 - 192.168.10.128 /30
Network 5 - 192.168.10.132 /30
A. RIP version 1
B. RIP version 2
C. IGRP
D. EIGRP
E. OSPF

Answer: B,D,E

QUESTION NO: 317
Which of the following describe the process identifier that is used to run OSPF on a router?
(Choose two.)
A. It is locally significant.
B. It is needed to identify a unique instance of an OSPF database.
C. All routers in the same OSPF area must have the same process ID if they are to exchange
routing information.
D. It is globally significant.
E. It is an optional parameter required only if multiple OSPF processes are running on the router.

Answer: A,B

QUESTION NO: 319
Which one of the following OSPF network types needs to select a BDR?
A. point-to-multipoint and multiaccess
B. nonbroadcast and broadcast multipoint
C. point-to-point and point-to-multipoint
D. point-to-point and multi-access
E. nonbroadcast and broadcast multiaccess

Answer: E
Explanation:
When selecting DR and BDR in the NBMA network, OSPF will use the unicast mode. By adjusting the hello/dead timers you can make non-compatible OSPF network types appear as neighbors via the "show ip ospf neighbor" but they won't become "adjacent" with each other. OSPF network types that use a DR (broadcast and non-broadcast) can neighbor with each other and function properly. Likewise OSPF network types (point-to-point and point-to-multipoint) that
do not use a DR can neighbor with each other and function properly. But if you mix DR types with non-DR types they will not function properly (i.e. not fully adjacent). You should see in the OSPF database "Adv Router is not-reachable" messages when you've mixed DR and non-DR types. OSPF has different Network Types Point-to-Point Point-to-Multipoint Broadcast Multi-Access Non-Broadcast Multi-Access OSPF will elect a DR and a BDR on Broadcast Multi-Access and Non-broadcast Access.

QUESTION NO: 328
On point-to-point networks, OSPF hello packets are addressed to which address?
A. 172.16.0.1
B. 254.255.255.255
C. 224.0.0.5
D. 127.0.0.1
E. 223.0.0.1
F. 192.168.0.5

Answer: C
Explanation:
The multicast IP address 224.0.0.5 is known as 'AllSPFRouters.' All routers running OSPF should
be prepared to receive packets sent to this address since hello packets are always sent to this
destination. Also, certain OSPF protocol packets are sent to this address during the flooding
procedure.
Incorrect Answers:
A: This is the IP address reserved for the internal loopback on PC hosts. All windows based PC's
will use this internal IP address, assuming that the TCP/IP stack is correctly installed. B, D. These
addresses are part of the range of addresses reserved for internal use, as defined in RFC 1918.

QUESTION NO: 329
OSPF routing uses the concept of areas. What are the characteristics of OSPF areas? (Choose
Three.)
A. Each OSPF area requires a loopback interface to be configured.
B. Areas may be assigned any number from 0 to 65535.
C. Area 0 is called the backbone area.
D. Hierarchical OSPF networks do not require multiple areas.
E. Multiple OSPF areas must connect to area 0.
F. Single area OSPF networks must be configured in area 1.

Answer: B,C,E

QUESTION NO: 331
Which items are correct about the routing protocol OSPF? (Choose three.)
A. It supports VLSM.
B. It increases routing overhead on the network.
C. It confines network instability to one area of the network.
D. It allows extensive control of routing updates.

Answer: A,C,D

QUESTION NO: 333
What are three characteristics of the OSPF routing protocol? (Choose three.)
A. It converges quickly.
B. OSPF is a classful routing protocol.
C. It uses cost to determine the best route.
D. It uses the DUAL algorithm to determine the best route.
E. OSPF routers send the complete routing table to all directly attached routers.
F. OSPF routers discover neighbors before exchanging routing information.

AnAnswer: A,C,F

When designing OSPF networks; what is the purpose of using a hierarchical design? (Select all choices that apply)
A. To reduce the complexity of router configuration
B. To speed up convergence
C. To confine network instability to single areas of the network
D. To reduce routing overhead
E. To lower costs by replacing routers
F. To decrease latency

Answer: B, C, D
Explanation:
An OSPF network designed in a hierarchical fashion with different areas is used because
a small change in the topology of a single area won't force every router to run the SPF
algorithm. Changes in one area are limited to that area only, not to every router within
the entire network. Confining the topology changes to one area reduces the overhead and
speeds the convergence of the network.
Reference: CCNA Self-Study CCNA ICND exam certification Guide (Cisco Press,
ISBN 1-58720-083-X) Page 194
Incorrect Answers:
A. This choice is incorrect because a hierarchical design actually adds complexity to the
router configuration.
E. This is incorrect because a hierarchical design will not eliminate the need for routers.
In fact, segmenting the network into multiple areas may actually require the use of
additional routers.
F. The use of a hierarchical design will in no way reduce the latency involved. If
additional routers are implemented in order to segment the network into additional areas,
then the latency involved may actually increase.

You are a network administrator and you need to implement a routing protocol on
your network that provides:
* Scalability
* VLSM support
* Minimal overhead
* Support for connecting networks using routers of multiple vendors
Which of the following routing protocol would best serve your needs?
A. VTP
B. RIP version 1
C. EIGRP
D. OSPF
E. IGRP

F. CDP
Answer: D
Explanation:
Since one of the requirements is that the routing protocol must support other vendors, our
only choices are RIP and OSPF. Since RIP version 1 does not support VLSM, OSPF is
the only choice.
Incorrect Answers:
A. VTP is the VLAN Trunking Protocol. This is not a routing protocol.
B. RIP version one does not support VLSM. Note that RIPv2 does support VLSM, and
would be a valid choice.
C, E: EIGRP and IGRP are Cisco proprietary routing protocols, and are not supported by
other vendors.
F. CDP is the Cisco Discovery Protocol, which is used to exchange information between
Cisco devices. It can only be used between Cisco routers and switches, and it is not a
routing protocol.

Which of the following routing protocols support the use of VLSM (Variable Length
Subnet Masking)? (Select three)
A. RIPv1
B. EIGRP
C. OSPF
D. IGRP
E. RIPv2

Answer: B, C, E
Explanation:
Static routing, OSPF, IS-IS, EIGRP, BGP, and RIP version 2 all support VLSM.
Incorrect Answers:
A, D: RIPv1 and IGRP do not support VLSM.
Reference: Sybex CCNA Study Guide edition 4, Page 123

You need to implement the use of a routing protocol that meets the following
requirements:
1. Converges quickly
2. Supports VLSM, CIDR, IP, and IPX.
3. Uses minimal bandwidth for routing updates.
Which one of the following routing protocols would be the best choice?
A. RIPv1
B. RIPv2
C. IGRP
D. OSPF
E. EIGRP

Explanation:
EIGRP would be the best choice as it provides support for VLSM and CIDR, has faster
convergence times than other protocols, is scalable, and supports IP, IPX, and AppleTalk.
EIGRP is a Cisco proprietary routing protocol, so it will not work with other vendors.
However, the requirements of the question made no mention of the use of non-Cisco
routers, so it will not be an issue in this case.
Incorrect Answers:
A, C: Both of these routing protocols do not support VLSM.
B. While RIPv2 supports VLSM, it provides no support for IPX. The IPX RIP protocol is
similar in function to RIP version 1. Both versions of RIP also consume more bandwidth
than EIGRP.
D. OSPF does not support IPX.

Which of the following routing protocols will support this IP addressing scheme?
(Choose all that apply).
A. RIP version 1
B. RIP version 2
C. IGRP
D. EIGRP
E. OSPF
F. BGP

Answer: B, D, E
Explanation:
Because this network is using IP subnets with variable length subnet masks, only routing
protocols that support VLSM will fit this particular case. The routing protocols that
support VLSM are RIP v2, EIGRP and OSPF.
Incorrect Answers:
A, C: RIP version 1 and IGRP do not support VLSM information within the routing
updates.
F. BGP is used for inter-AS routing, such as the Internet. It is not normally used as an
Interior routing protocol.

Router CK1 learns about a remote network from EIGRP, OSPF, and a static route.
Assuming all routing protocols are using their default administrative distance,
which route will CK1 use to forward data to the remote network?
A. The router will use the static route.
B. The router will use the OSPF route.
C. The route will use the EIGRP route.
D. The router will load balance and use all three routes.
E. None of the above

Answer: A
Explanation:
When a router learns about the same network via multiple sources, the router will choose
the source with the lowest administrative distance (AD). By default, the AD for these
routing protocols are:
Connected Interface has 0 AD
Static Route : 1
EIGRP : 90
OSPF : 110
So, the static route will be chosen since it has the lowest AD.

A Certkiller router learns two routes to a remote network, one route via OSPF and
one route via RIPv2. The network administrator wants the router to install the
route learned via RIPv2 into its routing table. What should the network
administrator configure to ensure that the router will use the route learned via RIPv2?
A. Nothing. The router will automatically use routes learned via RIP over routes learned
via OSPF.
B. The network administrator should configure the routers along the OSPF path with
lower priority numbers.
C. The network administrator should configure the router interface on the OSPF path to
be a passive interface.
D. The network administrator should configure an administrative distance for RIP that is
lower than the administrative distance of OSPF.
E. If two paths exist to a remote network, the only way to force the router to prefer one
path over the other is to configure the preferred path as a static route.

Answer: D
Explanation:
When multiple routing protocols are configured for the same networks, the router will
use the path with the lowest Administrative Distance (AD). By default, OSPF has and
AD of 110 and RIP has an AD of 120. In order to ensure that the router prefers the route
learned via RIP over OSPF, the AD of the RIP route must be reduced to a value less than
110.

You have been tasked with choosing a routing protocol that would best fit the needs
of the Certkiller network. Which routing protocol uses bandwidth and delay as
metrics, by default?
A. EIGRP
B. OSPF
C. BGP
D. RIPv1
E. RIPv2
F. None of the above

Answer: A

Non-contiguous networks can pose a problem for network reachability in certain
circumstances. Which of the following routing protocols have means of minimizing
the risk? (Select three choices)
A. RIP v1
B. RIP v2
C. EIGRP
D. IGRP
E. OSPF
F. VLSM

Answer: B, C, E
Explanation:
OSPF, RIP version 2, and EIGRP all provide support for discontiguous networks. This is
provided by the fact that subnet mask information is advertised along with the routes, and
these protocols all support Variable Length Subnet Masks (VLSM).
Incorrect Answers:
A. Whenever RIP version 1 advertises a network across a different major net boundary,
RIP summarizes the advertised network at the major net boundary. RIP version 2 is an
updated version of RIP, and one of the main features that it was able to provide over
RIPv1 is support for VLSM information.
D. IGRP does not support VLSM. Like RIP version 2, EIGRP is the updated version of
IGRP, which provides support for VLSM.
F. VLSM is the feature that is required to support non-contiguous networks, but VLSM is
not itself a routing protocol

Which of the following routing protocols are less likely prone to problems in non
contiguous networks? (Select all valid responses)
A. IGRP
B. ICMP
C. OSPF
D. RIP v1
E. RIP v2
F. EIGRP

Answer: C, E, F
Explanation:
OSPF, RIP v2, and EIGRP all support VLSM information, which will eliminate the
problems that can arise from non contiguous networks.
Incorrect Answers:
A, D. IGRP and RIP version 1 are distance vector routing protocols that do not support
VLSM information, so they are prone to problems that can arise from discontiguous
network schemes.
B. ICMP (Internet Control Message Protocol) is not a routing protocol. It is used
primarily for the management and monitoring of networks.

Which of the following statements describe the characteristic of link state routing
protocols? (Choose all that apply.)
A. The exchange of an advertisement is triggered by a change in the network.
B. All routers exchange routing tables with each other in a multipoint network.
C. Packets are routed based upon the shortest path to the destination.
D. Paths are chosen depending on the cost efficiency factor.
E. Every router in an OSPF area is capable of representing the entire network topology.
F. Only the designated router in an OSPF area can represent the entire network topology.

Answer: A, C, E
Explanation:
The predominant link state routing protocols are OSPF and IS-IS. The following
describes the features and functionality of OSPF:
Open Shortest Path First
* Each router discovers its neighbors on each interface. The list of neighbors is kept in a
neighbor table.
* Each router uses a reliable protocol to exchange topology information with its
neighbors.
* Each router places the learned topology information into its topology database.
* Each router runs the SPF algorithm against its own topology database.
* Each router runs the SPF algorithm against its own topology database to calculate the
best routes to each subnet in the database.
* Each router places the best roué to each subnet into the IP routing table.
The following list points out some of the key features of OSPF:
* Converges very quickly - from the point of recognizing a failure, it often can converge
in less than 10 seconds.
* Supports VLSM.
* Uses short Hello messages on a short regular interval, with the absence of hello
messages indicating that a neighbor is no longer reachable.
* Sends partial updates when link status changes and floods full updates every 30
minutes. The flooding, however, does not happened all at once, so the overhead s
minimal.
* Uses cost for the metric.
Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press,
ISBN 1-58720-094-5) Page 417

A large corporation that frequently integrates networks from newly acquired
businesses has just decided to use OSPF as the corporate routing protocol instead of
EIGRP. What two benefits will the change from EIGRP to OSPF provide to the
corporation? (Choose two)
A. The ability to automatically summarize networks
B. The ability to redistribute default and static routes
C. The ability to use VLSM
D. The ability to support multi-vendor routers
E. The ability to create a hierarchical design using areas

Answer: D, E
Explanation:
Open Shortest Path First (OSPF) is a routing protocol developed for Internet Protocol
(IP) networks by the Interior Gateway Protocol (IGP) working group of the Internet
Engineering Task Force (IETF). Unlike, EIGRP, OSPF is standards based which is
supported by multiple router vendors.
Unlike RIP and EIGRP, OSPF can operate within a hierarchy. The largest entity within
the hierarchy is the autonomous system (AS), which is a collection of networks under a
common administration that share a common routing strategy. OSPF is an intra-AS
(interior gateway) routing protocol, although it is capable of receiving routes from and
sending routes to other AS's.
An AS can be divided into a number of areas, which are groups of contiguous networks
and attached hosts. Routers with multiple interfaces can participate in multiple areas.
These routers, which are called Area Border Routers, maintain separate topological
databases for each area.

Certkiller 1 is a Backup Designated Router on the Certkiller OSPF network. On
which types of network will OSPF elect a BDR?
A. Nonbroadcast and broadcast multi-access
B. Point-To-Multipoint and multi-access
C. Point-To-Point and Point-To-multipoint
D. Point-To-Point and multi-access
E. NonBroadcast and Broadcast multipoint
F. None of the above

Answer: A
Explanation:DR and BDR are elected on broadcast and nonbroadcast multi-access networks.

Which of the following OSPF commands, when used together, will put the network
192.168.10.0/24 into OSPF area 0? (Select all valid responses)
A. Router(config-router)# network 192.168.10.0 0.0.0.255 0
B. Router(config-router)# network 192.168.10.0 0.0.0.255 area 0
C. Router(config-router)# network 192.168.10.0 255.255.255.0 area 0
D. Router(config)# router ospf 0
E. Router(config)# router ospf 1

Answer: B, E
Explanation:
B. The network command specifies the IP address (192.168.10.0) followed by the
wildcard mask (not the subnet mask), and the area that is to be associated with the OSPF
address range (in this case, area 0). The wildcard mask indicates in binary how much of
the IP address much be matched with 0s indicating that the bits must match and 1
indicating that they may vary. Thus 0.0.0.255 or
00000000.00000000.00000000.11111111 indicates that any bit in the last octet can vary
while all bits in the first 3 octets must match the network address (in other words,
192.168.10.xx)
E. The router ospf command enables OSPF routing and enters router configuration mode.
This command takes a <process-id> argument which identifies the OSPF process.
Incorrect Answers:
A. This command is correct, except for the fact that the keyword "area" is missing and
needs to be inserted.
C. For OSPF, the inverse mask must be used, not the regular subnet mask.
D. OSPF can not use process ID 0, and the goal of this question is to put a specific
network in area 0, not the entire routing process

Under which circumstance, i.e. network type, would an OSPF router establish a
neighbor adjacency, even though the DR/BDR election process was not performed?
A. Point-to-point
B. Broadcast multicast
C. Nonbroadcast multicast
D. Backbone area 0
E. Virtual Link

Answer: A
Explanation: If there's a point to point connection, there's no need for a designated
router or a backup designated router election. By definition, only two routers exist on a point to point connection.
Incorrect Answers:
B, C. In these network types, the potential for more than two routers on the segment
exist, so the Designated Router and Backup Designated Routers are elected.
D. This is not a network type. Area 0 is the backbone of any OSPF network.
E. Virtual Links are used in OSPF to link an area to area 0. Every area must be directly
connected to area 0 at some point, and virtual links are used for areas that do not meet
this requirement.

On the assumption that every OSPF router in a particular area is configured with
the same priority value; which secondary value would be used as a router ID when
there is no loopback interface set?
A. The IP address of the first Fast Ethernet interface.
B. The IP address of the console management interface.
C. The highest IP address among its active interfaces.
D. The lowest IP address among its active interfaces.
E. There will be no router ID until a loopback interface is configured.

Answer: C
Explanation: Ordinarily the loopback interface would be selected as the router ID.
In the event that no loopback interface is configured, the router ID will be the first
active interface that comes up on the router. If that particular interface has more
then one IP address, then the highest address will be selected as the Router ID.
Incorrect Answers:
B. Putting an IP address on the management console is a concept that is configured on a
Catalyst switch, not a router.

On the topic of OSPF routing; which of the following are the traits of an OSPF
area? (Select all that apply)
A. Each OSPF area requires a loopback interface to be configured.
B. Areas may be assigned any number from 0 to 65535.
C. Area 0 is called the backbone area.
D. Hierarchical OSPF networks do not require multiple areas.
E. Multiple OSPF areas must connect to area 0.
F. Single area OSPF networks must be configured in area 1.
G. None of the above

Answer: C, E
Explanation:
OPSF uses areas in a hierarchical fashion, and the backbone area is always area 0. All
other areas have at least one connection to area 0.
Incorrect Answers:
A. Loopback interfaces are often used in OSPF networks, so that the router ID can be
configured. However, this is not a requirement.
B. The area-id can be an integer between 0 and 4294967295.
F. Single area OSPF networks do not have to be configured with the backbone area 0.
Although area 1 can indeed be used, it is not required that area 1 is used. Single area
OSPF networks can be any integer from 0-4294967295.

If the bandwidth of an OSPF interface on a Certkiller router is configured with the
"bandwidth 64" command, what would be the calculated cost of the link?
A. 1
B. 64
C. 1562
D. 64000
E. 1500
F. None of the above

Answer: C
Explanation: The question states that OSPF interface has been configured with the
bandwidth 64command. Cisco IOS always interprets the values for the bandwidth
command as being in kbps, so the bandwidth is configured as 64 kbps. The metric
for any OSPF defaults to 100,000,000/bandwidth. So, in this example:
100,000,000 / 64000 = 1562.5

Certkiller is using OSPF as the routing protocol in their network. What are some of
the characteristics of this routing protocol? (Select all valid answer choices)
A. It confines network instability to a single area of network.
B. It increases the routing overhead of the network
C. It supports VLSM
D. It routes between Autonomous Systems.
E. It allows extensive control of routing updates

Answer: A, C, E
Explanation:
The following describes some of the features and functionality of the OSPF protocol:
Open Shortest Path First
* Each router discovers its neighbors on each interface. The list of neighbors is kept in a
neighbor table.
* Each router uses a reliable protocol to exchange topology information with its
neighbors.
* Each router places the learned topology information into its topology database.
* Each router runs the SPF algorithm against its own topology database.
* Each router runs the SPF algorithm against its own topology database to calculate the
best routes to each subnet in the database.
* Each router places the best roué to each subnet into the IP routing table.
The following list points out some of the key features of OSPF:
* Converges very quickly - from the point of recognizing a failure, it often can converge
in less than 10 seconds.
* Supports VLSM.
* Uses short Hello messages on a short regular interval, with the absence of hello
messages indicating that a neighbor is no longer reachable.
* Sends partial updates when link status changes and floods full updates every 30
minutes. The flooding, however, does not happened all at once, so the overhead s
minimal.
* Uses cost for the metric.
Incorrect Answers:
B. This is incorrect because the hierarchical design characteristics of OSPF actually
reduce the overhead on larger networks.
D. This is not true as OSPF doesn't route between Autonomous Systems. OSPF is an
IGP. Routing between autonomous systems is reserved for EGP protocols such as BGP.

Which of the following are true statements regarding the characteristics of OSPF
areas? (Select all that apply)
A. All OSPF networks require the use of multiple areas
B. Multiple OSPF areas must connect to area 0
C. Single area OSPF networks must be configured in area 1
D. Areas can be assigned any number from 0 to 63535
E. Area 0 is called the backbone area
F. Each OSPF area need to be configured with a loopback interface

Answer: B, E
Explanation:
OSPF divides its routing domain into areas. Area 0, the backbone, is required. This divides interior routing into two levels. If traffic must travel between two areas, the
packets are first routed to the backbone. This may cause non-optimal routes, since
interarea routing is not done until the packet reaches the backbone. Once there, it is
routed to the destination area, which is then responsible for final delivery. This layering permits addresses to be consolidated by area, reducing the size of the link state databases.
All areas must be connected to area 0, either directly or through the use of virtual links.
Incorrect Answers:
A. OSPF network can only consist of a single area.
C. Single area networks can use any area number. If more than one area is configured in
the network, then at least one of the areas must be area 0.
D. The area-id can be an integer between 0 and 4294967295.
F. While loopback interfaces are commonly used in OSPF networks, it is not a requirement.

On what kinds of networks does the OSPF protocol elect a backup designated
router? (Select all that apply)
A. Point-to-point
B. Point to multipoint
C. Broadcast
D. Non-broadcast multi-access
E. None of the above

Answer: C, D
Explanation:
The DR and BDR election process is performed on broadcast and non-broadcast
multi-access networks.
Incorrect Answers:
A, B: There is no DR or BDR on point to point and point to multipoint links. On a point to point link, only two routers exist so there is no need for a DR or BDR.

Certkiller uses OSPF in their WAN. The OSPF Hello protocol performs which of the
following tasks in this network? (Choose two)
A. It maintains neighbor relationships.
B. It broadcasts hello packets throughout the internetwork to discover all routers that are
running OSPF.
C. It uses timers to elect the router with the fastest links as the designated router.
D. It negotiates correctness parameters between neighboring interfaces.
E. It detects unreachable neighbors in 90 second intervals.
F. It provides dynamic neighbor discovery.
G. It is only used once when the router boots up

Answer: A, F

CK1 and CK2 are OSPF routers on a point-point link. On this point-to-point
network, OSPF hello packets are addressed to which address?
A. 192.168.0.5
B. 254.255.255.255
C. 223.0.0.1
D. 172.16.0.1
E. 224.0.0.5
F. 127.0.0.1
G. None of the above

e
Explanation:
The multicast IP address 224.0.0.5 is known as 'AllSPFRouters.' All routers running
OSPF should be prepared to receive packets sent to this address since hello packets are
always sent to this destination. Also, certain OSPF protocol packets are sent to this
address during the flooding procedure.
Incorrect Answers:
A. This is the IP address reserved for the internal loopback on PC hosts. All windows
based PC's will use this internal IP address, assuming that the TCP/IP stack is correctly
installed.
B, D. These addresses are part of the range of addresses reserved for internal use, as
defined in RFC 1918.

Which of the following statements below best describe the process identifier that is
used to run OSPF on a Certkiller router? (Choose two)
A. It is an optional parameter required only if multiple OSPF processes are running on
the router.
B. It is locally significant.
C. It is needed to identify a unique instance of an OSPF database.
D. All routers in the same OSPF area must have the same process ID if they are to
exchange routing information.
E. It is globally significant.
F. It is shared among all OSPF routers

Answer: B, C
Explanation:
The OSPF process ID is locally significant, and is only used by the local router to
discriminate between multiple OSPF processes. In any given OSPF network, the process
ID's do not need to match between neighboring routers. This is in contrast to other
routing protocols, such as EIGRP.
Additional info:
router ospf process-id
no router ospf process-id
process-id
Internally used identification parameter for an OSPF routing process. It is locally
assigned and can be any positive integer. A unique value is assigned for each OSPF
routing process.

Which one of the following privileged EXEC mode IOS show commands will display
the state of the OSPF DR/BDR (designated router / backup designated router)
election process?
A. CK1 # show ip ospf interface
B. CK1 # show ip ospf priority
C. CK1 # show ospf neighbor detail
D. CK1 # show ospf processes
E. CK1 # show ospf neighbor state
F. None of the above

Answer: A
Explanation:
This command will display the router ID of both the DR and the BDR on the network
segment that the particular interface is connected to.
Example:
Router1#show ip ospf interface ethernet 0Ethernet0 is up, line protocol is upInternet Address
10.10.10.1/24, Area 0Process ID 1, Router ID 192.168.45.1, Network Type BROADCAST, Cost:
10 Transmit Delay is 1 sec, State BDR, Priority 1Designated Router (ID) 172.16.10.1, Interface
address 10.10.10.2 Backup Designated router (ID) 192.168.45.1, Interface address 10.10.10.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:06
Index 1/1, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 2, maximum is 2
Last flood scan time is 0 msec, maximum is 4 msec Neighbor Count is 1, Adjacent neighbor
count is 1Adjacent with neighbor 172.16.10.1 (Designated Router) Suppress hello for 0
neighbor(s)

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