Cisco CCNA EIGRP OSPF RIPv2 Questions

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Question:

Refer to the exhibit. After adding R3 router on the network, no routing updates are being exchanged between R3 and the new location. All other interconnectivity and Internet access for the existing locations of the company are working properly.
The task is to identify the fault(s) and correct the router configuration to provide full connectivity between the routers.

Access to the router CLI can be gained by clicking on the appropriate host. All passwords on all routers are Cisco.

IP addresses are listed in the chart below.



Answer and Explanation:

Its advised that you should read the question properly so as to understand what you are asked to do. Firstly, in this case;  verify the configuration of the newly added router since it does not function properly. Use the show running-config command from the command line interface of R3 router, (it's also recommended to use this command on other routers on the network)



From the output above, we can verify that the Eigrp autonomous number (AS) of 22 configuration on router 3 is wrong. On other routers it is 212. If the AS numbers on routers in a network are mismatched, this will hinder the routers on that network from forming adjacency.

To resolve this problem, you re-configure router R3 using the following command:


R3>enable (remember to enter cisco as the password here)
R3#configure terminal
R3(config)#no router eigrp 22  (this will erase the initial configuration)
R3(config)#router eigrp 212
R3(config-router)#network 192.168.60.0
R3(config-router)#network 192.168.77.0
R3(config-router)#no auto-summary
R3(config-router)#end
R3#copy running-configstartup-config (remember to use this command after every configuration)

Verify the configuration on R1 router with the show running-config command:



You will notice that R3 network  is missing in the configuration . R3 network address need to be added for it to be linkable. Use the following command:

R1>enable (remember to enter cisco as password here)
R1#configure terminal
R1(config)#router eigrp 212
R1(config-router)#network 192.168.77.0
R1(config-router)#end
R1#copy running-config startup-config
After configuration, use the ping command from R3 to verify connectivity.

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Question:

To configure the router (R2-RC) click on the console host icon that is connected to a router by a serial console cable (shown in the diagram as a dashed black line)

Central Florida Widgets recently installed a new router in their office. Complete the network installation by performing the initial router configurations and configuring RIPV2 routing using the router command line interface (CLI) on the R2-RC.

Router configuration:

Name of the router is R2-RC
Enable-secret password is cisco1
The password to access user EXEC mode using the console is cisco2
The password to allow telnet access to the router is cisco3
IPV4 addresses must be configured as follows:


Ethernet network 209.165.202.128/27- router has last assignable host address in subnet
Serial network is 192.0.2.16/28- router has last assignable host address in the subnet. Interfaces should be enabled.
Router protocol is RIPV2   



Solution:

1. Configure router name:

Router>enable
Router#configure terminal
Router(config)#hostname R2-RC

2. Configure secret password:

R2-RC(config)# enable secret cisco1

3) Configure console Password:

R2-RC(config)#line console 0
R2-RC(config-line)#password cisco2
R2-RC(config-line)#login
R2-RC(config-line)#exit

4) Configure Telnet password:

R2-RC(config)#line vty 0 4
R2-RC(config-line)#password cisco3
R2-RC(config-line)#login
R2-RC(config-line)#exit

5) Assign IP address for Ethernet interface(Fa0/0):
Know or cram this table below; you might be given an opportunity to write it down before the exam:



Bit Value                    128     64     32     16     8     4         2        1

BitsBorrowed              1       2        3       4      5      6        7       8

Subnetmask              128    192    224  240   248   252     254   255
SubnetPrefix /CIDR   /25    /26   /27     /28   /29    /30


Normal 0 false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4

The Ethernet network 209.165.202.128/27: looking at the table above, you can see that the /27 has a bit value of 32 (increment) and mask should be 224 or /27

That means:

Network address: 209.165.202.128

Subnet mask: 255.255.255.224
Broadcast address: 209.165.202.159 (because 128 + 32 - 1 = 159)

Therefore, according to the question; the last assignable host address in this subnet should be: 209.165.202.158. Assign it to fa0/0 using these commands:
R2-RC(config)# interface fa0/0
R2-RC(config-if)#ip address 209.165.202.158 255.255.255.224
R2-RC(config-if)#no shutdown
R2-RC(config-if)#exit

6) Assign IP address for Serial interface(S0/0/0): (follow the same above)

Serial network 192.0.2.16 /28

Looking at the table above, you can see that the /28 has a bit value of 16 (increment) and mask should be 240 or /28

That means:

Serial network 192.0.2.16
Subnet mask: 255.255.255.240

Broadcast address:192.0.2.31 (because 16 + 16 - 1 = 31)

According to the question the last assignable host address in this subnet is 192.0.2.30. Assign it to s0/0/0 interface using the following command:

R2-RC(config)# interface s0/0/0
R2-RC(config-if)#ip address 192.0.2.30 255.255.255.240
R2-RC(config-if)#no shutdown
R2-RC(config-if)#exit

7) Configure RIP v2 routing protocol using the following command:

R2-RC(config)#router rip
R2-RC(config-router)#version 2
R2-RC(config-router)#network 209.165.202.128
R2-RC(config-router)#network 192.0.2.16
R2-RC(config-router)#end
R2-RC#copy running-configstartup-config  (don't forget this bit)

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Question 1

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 routers in the same OSPF area must have the same process ID if they are to exchange routing information.



Answer: A C

Question 2

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). What is the default administrative distance of the OSPF routing protocol?

A. 90
B. 100
C. 110
D. 20
E. 130
F. 170



Answer: C

Question 3

Which statements describe the routing protocol OSPF? (Choose three)

A. It supports VLSM.
B. It is used to route between autonomous systems.
C. It confines network instability to one area of the network.
D. It increases routing overhead on the network.
E. It allows extensive control of routing updates.
F. It is simpler to configure than RIPv2.



Answer: A C E

Explanation

Answer A and C are obviously correct. For answer E, it allows extensive control of routing updates via Link-State Advertisement (LSA). Administrators can filter these LSAs to meet their requirements easily.

Question 4

R1 is unable to establish an OSPF neighbor relationship with R3. What are possible reasons for this problem? (Choose two)



A. All of the routers need to be configured for backbone Area 1.
B. R1 and R2 are the DR and BDR, so OSPF will not establish neighbor adjacency with R3.
C. A static route has been configured from R1 to R3 and prevents the neighbor adjacency from being established.
D. The hello and dead interval timers are not set to the same values on R1 and R3.
E. EIGRP is also configured on these routers with a lower administrative distance.
F. R1 and R3 are configured in different areas.



Answer: D F

Explanation

A is not correct because the backbone area of OSPF is always Area 0.
B is not correct because R1 or R3 must be the DR or BDR -> it has to establish neighbor adjacency with the other.
C is not correct because OSPF neighbor relationship is not established based on static routing. It uses multicast address 224.0.0.5 to establish OSPF neighbor relationship.
E is not correct because configure EIGRP on these routers (with a lower administrative distance) will force these routers to run EIGRP, not OSPF.

D and F are correct because these entries must match on neighboring routers:

- Hello and dead intervals
– Area ID (Area 0 in this case)
– Authentication password
– Stub area flag

Question 5

Which address are OSPF hello packets addressed to on point-to-point networks?

A. 224.0.0.5
B. 172.16.0.1
C. 192.168.0.5
D. 223.0.0.1
E. 254.255.255.255



Answer: A

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Question 6

RouterD# show ip interface brief

Given the output for this command, if the router ID has not been manually set, what router ID will OSPF use for this router?

A. 10.1.1.2
B. 10.154.154.1
C. 172.16.5.1
D. 192.168.5.3



Answer: C

Explanation

The highest IP address of all loopback interfaces will be chosen -> Loopback 0 will be chosen as the router ID.

Question 7

ROUTER# show ip route
192.168.12.0/24 is variably subnetted, 9 subnets, 3 masks C 192.168.12.64 /28 is directly connected, Loopback1
C 192.168.12.32 /28 is directly connected, Ethernet0
C 192.168.12.48 /28 is directly connected, Loopback0
O 192.168.12.236 /30 [110/128] via 192.168.12.233, 00:35:36, Serial0
C 192.168.12.232 /30 is directly connected, Serial0
O 192.168.12.245 /30 [110/782] via 192.168.12.233, 00:35:36, Serial0
O 192.168.12.240 /30 [110/128] via 192.168.12.233, 00:35:36, Serial0
O 192.168.12.253 /30 [110/782] via 192.168.12.233, 00:35:37, Serial0
O 192.168.12.249/30 [110/782] via 192.168.12.233, 00:35:37, Serial0
O 192.168.12.240/30 [110/128] via 192.168.12.233, 00:35:36, Serial0

To what does the 128 refer to in the router output above?

A. OSPF cost
B. OSPF priority
C. OSPF hop count 5
D. OSPF ID number
E. OSPF administrative distance



Answer: A

Explanation

OSPF uses a metric referred to as cost. The cost of the entire path is the sum of the costs of the outgoing interfaces along the path. Cisco uses a simple formula to calculate OSPF cost:

OSPF cost = 108 / Bandwidth (byte)

Therefore, a 100 Mbps FastEthernet interface will have the cost of 108 / 100,000,000 (bytes) = 1

Note: Cost for interfaces with bandwidth equal or larger than 10^8 bps is normalized to 1 so a 1Gbps interface will also have OSPF cost of 1.

For "O 192.168.12.240 /30 [110/128] via 192.168.12.233, 00:35:36, Serial0″ line, the first number in the brackets is the administrative distance of the information source; the second number is the metric for the route -> In this case the second number is the OSPF cost.

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Question 8

The internetwork infrastructure of company XYZ 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. Corp-1
B. Corp-2
C. Corp-3
D. Corp4
E. Branch-1
F. Branch-2



Answer: D F

Explanation

There are 2 segments on the topology above which are separated by Corp-3 router. Each segment will have a DR so we have 2 DRs.

To select which router will become DR they will compare their router-IDs. The router with highest (best) router-ID will become DR. The router-ID is chosen in the order below:

+ The highest IP address assigned to a loopback (logical) interface.

+ If a loopback interface is not defined, the highest IP address of all active router's physical interfaces will be chosen.

In this question, the IP addresses of loopback interfaces are not mentioned so we will consider IP addresses of all active router's physical interfaces. Router Corp-4 (10.1.40.40) & Branch-2 (10.2.20.20) have highest "active" IP addresses so they will become DRs.

Question 9

What information does a router running a link-state protocol use to build and maintain its topological database? (Choose two)

A. hello packets
B. SAP messages sent by other routers
C. LSAs from other routers
D. beacons received on point-to-point links
E. routing tables received from other link-state routers
F. TTL packets from designated routers



Answer: A C