Testking_640-802_V13

Answer: B Explanation:

This "debug ip ospf events" output shown might appear if any of the following situations occurs:

1.The IP subnet masks for routers on the same network do not match.

2.The OSPF hello interval for the router does not match that configured for a neighbor.

3.The OSPF dead interval for the router does not match that configured for a neighbor. If a router configured for OSPF routing is not seeing an OSPF neighbor on an attached network, perform the following tasks:

1.Make sure that both routers have been configured with the same IP mask, OSPF hello interval, and OSPF dead interval.

2.Make sure that both neighbors are part of the same area type.

QUESTION NO: 25

The TestKing OSPF network is displayed below:

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The internetwork infrastructure of TestKing consists of a single OSPF area as shown in the graphic. There is concern that a lack of router resources is impeding internetwork performance. As part of examining the router resources, the OSPF DRs need to be known. All the router OSPF priorities are at the default and the router IDs are shown with each router.

Which routers are likely to have been elected as DR? (Choose two)

A.Testking-1

B.Testking-2

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C.Testking-3

D.Testking-4

E.Branch-1

F.Branch-2

Answer: D, F

Explanation:

DR and BDR election is done via the Hello protocol. Hello packets are exchanged via IP multicast packets (Appendix B) on each segment. The router with the highest OSPF priority on a segment will become the DR for that segment. The same process is repeated for the BDR. In case of a tie, the router with the highest RID will win. The default for the interface OSPF priority is one. Remember that the DR and BDR concepts are per multi-access segment. Setting the OSPF priority on an interface is done using the ip ospf priority <value> interface command.

A priority value of zero indicates an interface which is not to be elected as DR or BDR. The state of the interface with priority zero will be DROTHER. The following diagram illustrates the DR election:

In the above diagram, RTA and RTB have the same interface priority but RTB has a higher RID. RTB would be DR on that segment. RTC has a higher priority than RTB. RTC is DR on that segment.

The default RID is the highest IP address that is active in the router. Based on this info, router Testking-4 and Branch-2 will most likely be elected as the DR in their respective networks.

QUESTION NO: 26

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TestKing is using OSPF in their WAN. What is the maximum number of hops OSPF allows before it deems a network unreachable?

A.15

B.16

C.99

D.255

E.Unlimited

F.None of the above

Answer: E Explanation:

OSPF is a link state protocol. Link state protocols do not use hops to mark networks as unreachable. Instead OSPF implements a steady state operation to its adjacent neighbors by sending and receiving small Hello packets periodically. When an OSPF router does not receive a Hello packet for a specified time period, it assumes that the neighbor is down. The router then runs the SPF algorithm to calculate new routes.

Reference:

TestKing 640-801 Study Guide, Section 5.2 "Steady State Operation".

Incorrect Answers:

A.This is the maximum number of hops that a RIP network could use before the route is deemed unreachable.

B.When a RIP routes receives a routing update for a route that shows a hop count of 16, the route is considered to be unreachable. RIP routers use this to prevent packets from looping through the network indefinitely, but OSPF routers do not.

QUESTION NO: 27

On the topic of the OSPF hello protocol; which of the statements below are true? (Select two answer choices)

A.The OSPF Hello protocol provides dynamic neighbor discovery.

B.The OSPF Hello protocol detects unreachable neighbors in 90 second intervals.

C.The OSPF Hello protocol maintains neighbor relationships.

D.The OSPF Hello protocol negotiates correctness parameters between neighboring interfaces.

E.The OSPF Hello protocol uses timers to elect the router with the fastest links at the designated router.

F.The OSPF Hello protocol broadcast hello packets throughout the internetwork to discover all routers that are running OSPF.

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Answer: A, C

Explanation: The Hello Packet

OSPF contains a protocol (the Hello protocol) that is used to establish and maintain relationships between neighboring nodes. These relationships are called adjacencies. Adjacencies are the basis for the exchange of routing data in OSPF.

It is through the use of this protocol, and packet type, that an OSPF node discovers the other OSPF nodes in its area. Its name is intentionally significant; the Hello protocol establishes communications between potential neighboring routers. The Hello protocol uses a special subpacket structure that is appended to the standard 24-octet OSPF header. Together, these structures form a hello packet.

All routers in an OSPF network must adhere to certain conventions that must be uniform throughout the network. These conventions include the following:

1.The network mask

2.The interval at which hello packets will be broadcast (the hello interval)

3.The amount of time that must elapse before a non responding router will be declared dead (that is, the router dead interval) by the other routers in the network

4.All routers in an OSPF network must agree to use the same value for each of these parameters; otherwise, the network might not operate properly. These parameters are exchanged using hello packets. Together, they comprise the basis for neighborly communications. They ensure that neighbor relationships (known as adjacencies) are not formed between routers in different subnets and that all members of the network agree on how frequently to stay in contact with each other.

The hello packet also includes a listing of other routers (using their unique router IDs) that the source router has recently been in contact with. This field, the Neighbor field, facilitates the neighbor discovery process. The hello packet also contains several other fields such as Designated Router and Backup Designated Router. These fields are useful in maintaining adjacencies and support the operation of the OSPF network in both periods of stability and convergence.

QUESTION NO: 28

You are an administrator and you've just configured OSPF on a router with both physical and logical interfaces. Which of the following factors determine the router ID?

A. The lowest network number of any interface.

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B.The highest network number of any interface.

C.The highest IP address of any logical interface.

D.The middle IP address of any logical interface.

E.The lowest IP address of any physical interface.

F.The highest IP address of any physical interface.

G.The lowest IP address of any logical interface.

Answer: C Explanation:

Physical interface address is used only if there are no loopback addresses.

Sybex 5th p. 308:

"Router ID The Router ID (RID) is an IP address used to identify the router. Cisco chooses the Router ID by using the highest IP address of all configured loopback interfaces. If no loopback interfaces are configured with addresses, OSPF will choose the highest IP address of all active physical interfaces."

QUESTION NO: 29

Under which network type circumstance would an OSPF router establish router adjacencies while not performing the DR/BDR election process?

A.Point-to-point

B.Broadcast

C.Non-broadcast multi-access

D.Backbone area 0

E.None of the above

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 since only two routers can exist on a point to point network segment.

Incorrect Answers:

B, C. All OSPF routers in a broadcast and non-broadcast multi-access network go through the DR and BDR election process.

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D. The backbone area is not a network type, but a collection of OSPF networks links. Area 0 is reserved as the backbone area, and routers within area 0 may or may not go through the DR/BDR election process, depending on the network type.

QUESTION NO: 30

On the topic of OSPF routing; which of the following are the traits of an OSPF area? (Select 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.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: C, D, 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. If, for some reason, any area does not have a direct connection to the backbone area 0, then an OSPF virtual link must be configured. OSPF networks do not require multiple areas, as all routers can be contained within a single area. If an OSPF network is configured as a single area, then area 0 does not need to be used.

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.

QUESTION NO: 31

Router TK1 is running OSPF. What is the default administrative distance (AD) of this protocol?

A.90

B.100

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C.110

D.120

E.170

F.None of the above

Answer: C Explanation:

The administrative distance values are configured on a single router and are not exchanged with other routers. Table lists the various sources of routing information, along with the default administrative distance.

Default Administrative Distances

QUESTION NO: 32

Router TK1 is running OSPF. On this router, what kind of packets does OSPF send to keep up connectivity with its neighboring routers?

A.SPF packets

B.hello packets

C.keepalive packets

D.dead interval packets

E.LSU packets

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F. None of the above

Answer: B Explanation:

Hello packets simply identify the subnet, the router sending the packets and a few other details. As long as a router continues to receive Hellos form existing neighbors, the attached link must still be usable, and the neighbor that sent the Hello must still be up and working.

Reference: CCNA Self-Study CCNA ICND Exam Certification Guide (Cisco Press, ISBN 1-58720-083-X) Page 192 -193

Incorrect Answers:

A, E. SPF (shortest path first) and LSU (link state update) packets are not used to maintain connectivity between neighbors.

C. Keepalive packets do not exist. Hello packets perform the functions of a keepalive packet.

QUESTION NO: 33

Part of the TestKing OSPF network is shown below:

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In the TestKing network shown above, all of the routers are operational and OSPF has converged, what will be the output from the show ip route command issued on the Border router?

A.Gateway of last resort is 10.10.10.6 of network 0.0.0.0 10.0.0.0/30 is subnetted, 1 subnets

C 10.10.10.4 is directly connected, Serial0/2 192.168.255.0/30 is subnetted, 3 subnets

C 192.168.255.20 is directly connected, Serial0/0 C 192.168.255.16 is directly connected, Serial0/1

O 192.168.255.24[110/128]via 192.168.255.22, 00:12:40, Serial0/0 O 192.168.2.0/24[110/138]via 192.168.255.22, 00:12:40, Serial0/0 S* 0.0.0.0/0[1/0] via 10.10.10.6

B.Gateway of last resort is 10.10.10.6 of network 0.0.0.0 10.0.0.0/30 is subnetted, 1 subnets

C 10.10.10.4 is directly connected, Serial0/2 192.168.255.0/30 is subnetted, 3 subnets

C 192.168.255.20 is directly connected, Serial0/0 C 192.168.255.16 is directly connected, Serial0/1

O 192.168.255.24[110/128]via 192.168.255.22, 00:12:40, Serial0/1 O 192.168.2.0/24[110/1572]via 192.168.255.18, 00:00:11, Serial0/0 S* 0.0.0.0/0[1/0] via 10.10.10.6

C.Gateway of last resort is 10.10.10.6 of network 0.0.0.0 10.0.0.0/30 is subnetted, 1 subnets

C 10.10.10.4 is directly connected, Serial0/2 192.168.255.0/30 is subnetted, 3 subnets

C 192.168.255.20 is directly connected, Serial0/0 C 192.168.255.16 is directly connected, Serial0/1

O 192.168.255.24[110/128]via 192.168.255.22, 00:12:40, Serial0/0 O 192.168.2.0[110/1572]via 192.168.255.18, 00:00:11, Serial0/1 S* 0.0.0.0/0[1/0] via 10.10.10.6

D.Gateway of last resort is 10.10.10.6 of network 0.0.0.0 10.0.0.0/30 is subnetted, 1 subnets

C 10.10.10.4 is directly connected, Serial0/2 192.168.255.0/20 is subnetted, 3 subnets

C 192.168.255.20 is directly connected, Serial0/0 C 192.168.255.16 is directly connected, Serial0/1

O 192.168.255.24[110/128]via 192.168.255.22, 00:12:40, Serial0/0 O 192.168.2.0[110/1572]via 192.168.255.18, 00:00:11, Serial0/1 [110/1572]via 192.168.255.22, 00:00:07, Serial0/0

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