Quick Reference

Tuesday, April 17, 2007

CCNA Exam Topic : Troubleshooting 2

Continue of Troubleshooting CCNA actual exam questions.

Question 17:
Refer to the exhibit. All switch ports are assigned to the correct VLANs, but none of the hosts connected to SwitchA can communicate with hosts in the same VLAN connected to SwitchB. Based on the output shown, what is the most likely problem?

A. The access link needs to be configured in multiple VLANs.
B. The link between the switches is configured in the wrong VLAN.
C. The link between the switches needs to be configured as a trunk.
D. VTP is not configured to carry VLAN information between the switches.
E. Switch IP addresses must be configured in order for traffic to be forwarded between the switches.

Answer: C

For VLAN information to travel from one switch to another within the same VLAN we need to configure the link port between switches as trunk ports.
Switchport mode trunk

Question 18:
Refer to the exhibit. The network administrator normally establishes a Telnet session with the switch from host A. However, host A is unavailable. The administrator's attempt to telnet to the switch from host B fails, but pings to the other two hosts are successful. What is the issue?
A. Host B and the switch need to be in the same subnet.
B. The switch interface connected to the router is down.
C. Host B needs to be assigned an IP address in VLAN 1.
D. The switch needs an appropriate default gateway assigned.
E. The switch interfaces need the appropriate IP addresses assigned.

Answer: D

Ping was successful form host B to other hosts because of intervlan routing configured on router. But to manage switch via telnet the VLAN32 on the switch needs to be configured interface vlan32 along with ip address and its appropriate default-gateway address.
Since VLAN1 interface is already configure on switch Host A was able to telnet switch.

Question 19:
Refer to the exhibit. Configuration of both switches has been completed. During testing, the network administrator notices that users on SwitchA can not connect with users in the same VLAN on SwitchB. What should be done to solve this problem?

A. Ensure that the IP address of SwitchA is on the same network as the IP address of SwitchB.
B. Ensure that the same interface number is used to connect both switches.
C. Ensure that the ports connecting the two switches are configured to trunk.
D. Ensure that SwitchA and SwitchB are connected with a straight-through cable.

Answer: C

For VLAN information to communicate from one switch to another within the same VLAN we need to configure the link port (Fa0/3 switchA and fa0/4 switchB) between switches as trunk ports.

Switchport mode trunk

Question 20:
Refer to the exhibit. The switches have been configured with static VLANs as shown. During testing, the network administrator notices that VLAN 20 on SwitchA has no connectivity with VLAN 30 on SwitchB. What should the network administrator do?

A. Configure the interconnected ports on SwitchA and SwitchB into access mode.
B. Connect the two switches with a straight-through cable.
C. Add a Layer 3 device to connect VLAN 20 and VLAN 30.
D. Configure the management VLAN with IP addresses.
E. Ensure that the VTP passwords match on both switches.

Answer: C

To enable connectivity between two different VLAN we need to add a layer 3 device and configure interVLAN routing on it.

Question 21:
Refer to the exhibit. The two connected ports on the switch are not turning orange or green. What would be the most effective steps to troubleshoot this physical layer problem? (Choose three.)

A. Ensure that the Ethernet encapsulations match on the interconnected router and switch ports.
B. Ensure that cables A and B are straight-through cables.
C. Ensure cable A is plugged into a trunk port.
D. Ensure the switch has power.
E. Reboot all of the devices.
F. Reseat all cables.

Answer: BDF


Question 22:
Refer to the exhibit. A network administrator needs to add a new VLAN, named VLAN3, to the network shown. Unfortunately, there is not another FastEthernet interface on R1 to connect to the new VLAN3. Which approach is the most cost effective solution for this problem?
A. Purchase a new FastEthernet module and install it on R1.
B. Replace R1 with a new router that has at least three FastEthernet interfaces.
C. Configure a second switch to support VLAN3 with a VLAN trunk between SW1 and the new switch.
D. Configure a single VLAN trunk between R1 and SW1 and configure a subinterface on the R1 interface for
each VLAN.
E. Connect another router to a serial interface of R1. Use a FastEthernet interface on the new router for VLAN3..

Answer: D

Create sub interfaces on R1 for each VLAN this way we can save physical ports and be more cost effective , make the port connecting the R1 from switch has trunk port to carry all VLAN information.

Question 23:
Refer to the exhibit. S0/0 on R1 is configured as a multipoint interface to communicate with R2 and R3 in this hub-and-spoke Frame Relay topology. While testing this configuration, a technician notes that pings are successful from hosts on the network to hosts on both the and networks. However, pings between hosts on the and networks are not successful. What could explain this connectivity problem?
A. The ip subnet-zero command has been issued on the R1 router.
B. The RIP v2 dynamic routing protocol cannot be used across a Frame Relay network.
C. Split horizon is preventing R2 from learning about the R3 networks and R3 from learning about the R2 networks.
D. The and networks are overlapping networks that can be seen by R1, but not between R2 and R3.
E. The network used on the Frame Relay links is creating a discontiguous network between the R2 and R3 router subnetworks.

Answer: C

Split horizon by default does not allow routing updates to go in and out of the same interface.

Question 24:
While troubleshooting a connectivity problem, a network administrator notices that a port status LED on a Cisco Catalyst series switch is alternating green and amber. Which condition could this indicate?

A. The port is experiencing errors.
B. The port is administratively disabled.
C. The port is blocked by spanning tree.
D. The port has an active link with normal traffic activity.

Answer: A

Port Status
Off No link.
Solid green Link operational (with no link activity).
Flashing green Link operational (with activity). .
Alternating green and amber Link fault. Error frames can affect connectivity, and errors such as excessive collisions, CRC errors, and alignment and jabber errors are monitored for a link-fault indication.
Solid amber Port is not forwarding. For example, this could be because the port was disabled by management, suspended due to an address violation, or suspended by Spanning-Tree Protocol due to the presence of network loops.

Question 25:
Refer to the exhibit. Users on WS1 and WS2 are unable to reach the SR1 and SR2 servers to gain the files needed. A ping from the workstations WS1 and WS2 to the gateway address is successful. Which IOS command should the IT administrator issue on RTA to troubleshoot the problem?

A. show ip route
B. configure terminal
C. show startup-config
D. show ip interface FastEthernet0/0

Answer: A

show ip route command displays the routing table which provides the information about networks the router has routes.

Question 26:
Refer to the exhibit. HostA cannot ping HostB. Assuming routing is properly configured, what could be the cause of this problem?A. HostA is not on the same subnet as its default gateway.
B. The address of SwitchA is a subnet address.
C. The Fa0/0 interface on RouterA is on a subnet that can't be used.
D. The serial interfaces of the routers are not on the same subnet.
E. The Fa0/0 interface on RouterB is using a broadcast address.

Answer: D

For IP address /27 host range are -
And for IP address /27 host range are – Because both serial interfaces IPs are configured for different subnet the routing is not possible between both routers.

Question 27:
The system LED is amber on a Cisco Catalyst 2950 series switch. What does this indicate?
A. The system is malfunctioning.
B. The system is not powered up.
C. The system is powered up and operational.
D. The system is forwarding traffic.
E. The system is sensing excessive collisions.

Answer: A


See question number 24.

Question 28:
Refer to the exhibit. Serial0/0 does not respond to a ping request from a host on the FastEthernet0/0 LAN.How can this problem be corrected?

A. Enable the Serial 0/0 interface.
B. Correct the IP address for Serial 0/0.
C. Correct the IP address for FastEthernet 0/0.
D. Change the encapsulation type on Serial 0/0.
E. Enable autoconfiguration on the Serial 0/0 interface.

Answer: A

Need to run the command no shutdown to enable the serial 0/0 from administratively down to up state.

Question 29:

Refer to the exhibit. Connectivity cannot be made to the Internet. As part of the troubleshooting process, the user issued the ipconfig command, which generated the output shown in the exhibit. What step should the user take next in the troubleshooting process?

C:\Documents and Settings\host>ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection

IP Address. . . . . . . . . . . . :

Subnet Mask . . . . . . . . . . . :

Default Gateway . . . . . . . . . :
C:\Documents and Settings\host>ping
Pinging with 32 bytes of data:

Request timeout, Request timeout, request timeout.

A. Replace the NIC.
B. Reload the NIC driver.
C. Check the IP host address.
D. Check the default gateway address.
E. Check connectivity to the DNS server.

Answer: D


Verify the default-gateway address and check is it powered ON.

Question 30:
Refer to the exhibit. The Bigtime router is unable to authenticate to the Littletime router. What is the cause of the problem?
A. The usernames are incorrectly configured on the two routers.
B. The passwords do not match on the two routers.
C. CHAP authentication cannot be used on a serial interface.
D. The routers cannot be connected from interface S0/0 to interface S0/0.
E. With CHAP authentication, one router must authenticate to another router. The routers cannot be configured to authenticate to each other.

Answer: B


Configure the usernames and passwords. To do so, issue the username username password password command, where username is the hostname of the peer (neighbor). Ensure that:
· Passwords are identical at both ends.
The router name and password are exactly the same, because they are case-sensitive.

Question 31:
Refer to the exhibit. A technician is testing connection problems in the internetwork. What is the problem indicated by the output from HostA?

A. The routing on Router2 is not functioning properly.
B. An access list is applied to an interface of Router3.
C. The Fa0/24 interface of Switch1 is down.
D. The gateway address of HostA is incorrect or not configured.

Answer: D

Please comment if you have any doubts on troubleshooting Questions ...


Wealth said...

i want to believe the answer to question 31 is A i.e routing is not working properly. your answer is wrong in the sense that the gateway was pinged and their was reply.

a3tips said...

Hi wealth,

The output also shows tracert result for a host

Destination Host Unreachable
This error message means that no local or remote route exists for a destination host at the sending host or at a router. Troubleshoot the local host or the router's routing table.
Check this link

For our question 31 the problem must be on host or the router (router 1)

Since the answer D :The gateway address of HostA is incorrect or not configured.

Yes we can ping the gateway even if defualt gateway is not configured on host because both are on same network.
For routing to different network we need default gateway configured or correctly on host.


Wealth said...

thanks i can see your point. you're right. thanks

Mamoun said...

Dear a3tips,
Your blog is great... in Q25, Troubleshooting2, what are those IP addresses attached to serial links and ethernet links?
I know an IP is related to a port or interface, but not a cable or connection... I'm confused.

a3tips said...

Hi mamoun,
The IP address on Q25 actually represent the serial link ,fastethernet interfaces and hosts configured addresses.

You find the network address on the links and last octet address (.1) on the interfaces for understanding the question graphically.


Anonymous said...

Question 18: I think this one is really unfortunate...

The confusion here comes from the question, it says that host B can ping other two hosts. So if B can ping A, which is in the same VLAN 1 as given switch IP address, I don't see the reason why it wouldn't be able to telnet to the same VLAN 1 IP address??!!

As I said, I think the question is contradicting.

Look at it this way: B wants to telnet to an IP address that's not in it's subnet, so it broadcasts ARP request which hits Router subinterface Vlan32. Since all Vlans on the exhibit are on the same interface and directly connected, router will know where to direct the packet and replies with it's own MAC address. So host B sends a frame to the router. Frame contains an IP packet for Vlan1 IP address. As layer 3 device, router will find the Vlan1 IP address in it's route table (directly connected) and pass it onto the subinterface via trunk to VLAN1 and hit the destination. Please explain why it wouldn't happen this way?

Again, thanks for help and keep the good work.

If I pass, I'll make a donation. I think everybody should, as much as they can afford.


a3tips said...

Hi Alex,

Your query:
The confusion here comes from the question, it says that host B can ping other two hosts. So if B can ping A, which is in the same VLAN 1 as given switch IP address, I don't see the reason why it wouldn't be able to telnet to the same VLAN 1 IP address??!!

Q18 further to my explanation yes your correct in your query explanation but only still at network layer(layer 3) that is reaching the destination ip address (Switch).

Since telnet works at layer 7 (application layer) so as to manage a switch it needs interface vlan 32 and default-gateway configured on switch.

Hope this helps..


Anonymous said...

Should not question 26 have the ip address range in the answer description for ip be a range of to instead of as stated?

a3tips said...


Yes you are correct
the range for ip is to instead of


Anonymous said...

Hi Alex,

Your query:
The confusion here comes from the question, it says that host B can ping other two hosts. So if B can ping A, which is in the same VLAN 1 as given switch IP address, I don't see the reason why it wouldn't be able to telnet to the same VLAN 1 IP address??!!

Host A and Host B are not on the same VLAN, Host A is in VLAN 1 while Host B is in VLAN 32.


Anonymous said...

Option D of Question no. 31 is incorrect as if we are able to ping default gateway thet means it is correctly configured
So correct ans is A

a3tips said...

check above comments section for q31 clarification..


Anonymous said...


I just want to add.

On Q.26.

When you configure fa0/0 first, before Serial 0/0:

Serial interface of RouterA is /27 overlaps fa0/0 interface, /27.

Network Address:
Usable Address: -
Broadcast Address:

But what if Serial 0/0 being configured first?

C could be the answer.

C. The Fa0/0 interface on RouterA is on a subnet that can't be used.
Router will notify you with this:
% overlaps with FastEthernet0/0
Which is indeed subnet of Serial interface.

But, Its best to choose D. Because of the impact of changing subnets on fastethernet interface.