VTP Questions

Here you will find answers to VTP Questions

Note: If you are not sure about VTP, please read my VTP tutorial and the VTP Flash tutorial by Cisco.

Question 1

Switch R1 and R2 both belong to the Company VTP domain. What’s true about the switch operation in VTP domains? (Choose two)

A. A switch can only reside in one management domain
B. A switch is listening to VTP advertisements from their own domain only
C. A switch is listening to VTP advertisements from multi domains
D. A switch can reside in one or more domains
E. VTP is no longer supported on Catalyst switches

Answer: A B

Explanation

A VTP domain (also called a VLAN management domain) is made up of one or more network devices that share the same VTP domain name and that are interconnected with trunks. A network device can be configured to be in one and only one VTP domain -> A is correct.

If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name and the VTP configuration revision number. The switch ignores advertisements with a different management domain name or an earlier configuration revision number -> B is correct.

(Reference: http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/vtp.html)

Note: Just for your information, if a switch has not belonged to any VTP domain yet and it receives a VTP advertisement with a VTP domain (whose password is not set), it will join that domain automatically.

Question 2

How does VTP pruning enhance network bandwidth?

A. by restricting unicast traffic to across VTP domains
B. by reducing unnecessary flooding of traffic to inactive VLANs
C. by limiting the spreading of VLAN information
D. by disabling periodic VTP updates

Answer: B

Explanation

VTP Pruning makes more efficient use of trunk bandwidth by forwarding broadcast and unknown unicast frames on a VLAN only if the switch on the receiving end of the trunk has ports in that VLAN.

The following example shows the operation of a VTP domain without and with VTP Pruning.

Without VTP Pruning:

VTP domain without VTP Pruning

When PC A sends a broadcast frame on VLAN 10, it travels across all trunk links in the VTP domain. Switches Server, Sw2, and Sw3 all receive broadcast frames from PC A. But only Sw3 has user on VLAN 10 and it is a waste of bandwidth on Sw2. Moreover, that broadcast traffic also consumes processor time on Sw2. The link between switches Server and Sw2 does not carry any VLAN 10 traffic so it can be “pruned”.

VTP domain with VTP Pruning

-> B is correct.

Question 3

VTP devices in a network track the VTP revision number. What is a VTP configuration revision number?

A. A number for identifying changes to the network switch.
B. A number for identifying changes to the network router.
C. A number for identifying changes to the network topology.

Answer: C

Question 4

VTP switches use advertisements to exchange information with each other. Which of the following advertisement types are associated with VTP? (Choose three)

A. Domain advertisements
B. Advertisement requests from clients
C. Subset advertisements
D. Summary advertisements

Answer: B C D

Explanation

All VTP packets contain these fields in the header:

* VTP protocol version: 1, 2, or 3
* VTP message types:
1) Summary advertisements (inform adjacent Catalysts of the current VTP domain name and the configuration revision number)
2) Subset advertisement (is sent following the summary advertisement and contains a list of VLAN information)
3) Advertisement requests (is needed in the case it is reset, the VTP domain name has been changed or it has received a VTP summary advertisement with a higher configuration revision than it own).

(For more information about these VTP types, please read: http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml)

4) VTP join messages (similar to the Advertisement request messages but with a different Message Type field value and a few more parameters, including VTP domain name, and a VLAN bit string. If the bit is set, flooded traffic for that VLAN should be received on that trunk. Each trunk port maintains a state variable per VLAN – Joined/Pruned. If the state is Joined, the trunk port is allowed to send broadcast and flooded unicast traffic on this VLAN. If the state is Pruned, the trunk port will not send the broadcast or flooded unicast traffic on this VLAN. VTP join messages are sent when the VTP Client first joins a VTP domain to inform the VTP Servers about its existence in that VTP domain).
* Management domain length
* Management domain name

Question 5

The lack of which two prevents VTP information from propagating between switches? (Choose two)

A. A root VTP server
B. A trunk port
C. VTP priority
D. VLAN 1

Answer: B D

Explanation

VTP advertisements only travel through trunk ports -> B is correct.

VLAN 1 is a special VLAN selected by design to carry specific information such as CDP (Cisco Discovery Protocol), VTP, PAgP and DTP. This is always the case and cannot be changed. Cisco recommends not to use VLAN 1 as a standard VLAN to carry network data -> D is correct.

Question 6

Which two DTP modes will permit trunking between directly connected switches? (Choose two)

A. dynamic desirable (VTP domain A) to dynamic desirable (VTP domain A)
B. dynamic desirable (VTP domain A) to dynamic desirable (VTP domain B)
C. dynamic auto (VTP domain A) to dynamic auto (VTP domain A)
D. dynamic auto (VTP domain A) to dynamic auto (VTP domain B)
E. dynamic auto (VTP domain A) to nonegotiate (VTP domain A)
F. nonegotiate (VTP domain A) to nonegotiate (VTP domain B)

Answer: A F

Explanation

Below is the switchport modes for easy reference:

Mode	Function
Dynamic Auto	Creates the trunk based on the DTP request from the neighboring switch.
Dynamic Desirable	Communicates to the neighboring switch via DTP that the interface would like to become a trunk if the neighboring switch interface is able to become a trunk.
Trunk	Automatically enables trunking regardless of the state of the neighboring switch and regardless of any DTP requests sent from the neighboring switch.
Access	Trunking is not allowed on this port regardless of the state of the neighboring switch interface and regardless of any DTP requests sent from the neighboring switch.
Nonegotiate	Forces the port to permanently trunk but prevents the interface from generating DTP frames. This command can be used only when the interface switchport mode is access or trunk. You must manually configure the neighboring interface as a trunk interface to establish a trunk link.

Note: If an interface is set to switchport mode dynamic desirable, it will actively attempt to convert the link into trunking mode. If the peer port is configured as switchport mode trunk, dynamic desirable, or dynamic auto mode, trunking is negotiated successfully -> A is correct.

B is not correct because 2 dynamic desirable mode in 2 different VTP domains cannot create a trunk link.

Dynamic auto waits to receive DTP from the neighbor so if 2 interfaces are set to this mode, none of them will receive DTP frames -> C and D are not correct.

A port in Nonegotiate mode can be set to access or trunk port mode but it will not send DTP. Dynamic auto also does not send DTP -> a trunk link cannot be created -> E is not correct.

Also, when setting ports to nonegotiate, that port will not send DTP. We can set both interfaces to trunk link -> a trunk link can be created between two different VTP domains -> F is correct.

Question 7

The Company switches are configured to use VTP. What’s true about the VLAN trunking protocol (VTP)? (Choose two)

A. VTP messages will not be forwarded over nontrunk links.
B. VTP domain names need to be identical. However, case doesn’t matter.
C. A VTP enabled device which receives multiple advertisements will ignore advertisements with higher configuration revision numbers.
D. A device in “transparent” VTP v.1 mode will not forward VTP messages.
E. VTP pruning allows switches to prune VLANs that do not have any active ports associated with them.

Answer: A D

Explanation

Answer A is obviously correct as VTP advertisements only travel through trunk ports.

VTP domain names are case-sensitive. That means the domain “certprepare” is different from “Certprepare”. There is no exception -> B is not correct.

A VTP enabled device which receives multiple advertisements will update (not ignore) advertisements with higher configuration revision numbers, provided that it has the same VTP domain name and password -> C is not correct.

Answer D is not clear. In VTP Version 1, a VTP transparent switch inspects VTP messages for the domain name and version and forwards a message only if the version and domain name match. Because VTP Version 2 supports only one domain, it forwards VTP messages in transparent mode without inspecting the version and domain name. So in this case we don’t have enough information to conclude about answer D.

Answer E is not clear too. VTP will prune VLANs on trunks connected to switches that do not have ports associated with the VLANs. I am not sure what Cisco wants to say in answer E.

But if we consider answer E to be incorrect then the best answers should be A and D.

(Reference: http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_50_se/configuration/guide/swvtp.html#wp1035121)

Question 8

The Company switches have all been upgraded to use VTP version 2. What are two benefits provided in VTP Version 2 that are not available in VTP Version 1? (Choose two)

A. VTP version 2 supports Token Ring VLANs.
B. VTP version 2 allows VLAN consistency checks.
C. VTP version 2 saves VLAN configuration memory.
D. VTP version 2 reduces the amount of configuration necessary.
E. The VTP version 2 allows active redundant links when used with spanning tree.

Answer: A B

Explanation

The major difference is that VTP V2 introduces support for Token Ring VLANs. If you use Token Ring VLANs, you must enable VTP V2 -> A is correct.

In VTP version 2, VLAN consistency checks (such as VLAN names and values) are performed only when you enter new information through the command-line interface (CLI) or Simple Network Management Protocol (SNMP). Consistency checks are not performed when new information is obtained from a VTP message or when information is read from NVRAM. If the digest on a received VTP message is correct, its information is accepted without consistency checks -> B is correct.

(Reference: http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml)

Question 9

Switch R1 is configured to use the VLAN Trunking Protocol (VTP). What does R1 advertise in its VTP domain?

A. The VLAN ID of all known VLANs, the management domain name, and the total number of trunk links on the switch.
B. The VLAN ID of all known VLANs, a 1-bit canonical format (CF1 Indicator), and the switch configuration revision number.
C. The management domain name, the switch configuration revision number, the known VLANs, and their specific parameters.
D. A 2-byte TPID with a fixed value of 0×8100 for the management domain number, the switch configuration revision number, the known VLANs, and their specific parameters.

Answer: C

Explanation

VTP advertises its management domain name, the switch configuration revision number, the known VLANs, and their specific parameters -> C is correct.

Note: IEEE 802.1Q VLAN (not VTP) tag uses the tag protocol identifier (TPID) field to identify the protocol type. The Default TPID value in IEEE 802.1Q, is 0×8100 -> D is not correct.

Question 10

Which two statements correctly describe VTP? (Choose two.)

A. Transparent mode always has a configuration revision number of 0.
B. Transparent mode cannot modify a VLAN database.
C. Client mode cannot forward received VTP advertisements.
D. Client mode synchronizes its VLAN database from VTP advertisements.
E. Server mode can synchronize across VTP domains.

Answer: A D