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ICND2 – DTP Questions

October 31st, 2017 in ICND2 200-105 Go to comments

Question 1

Explanation

Control traffic like CDP, DTP, PAgP, and VTP uses VLAN 1 to operate, even if you change the native VLAN.

Question 2

Explanation

Although some books and websites said DTP is disabled if the switch port is configured as trunk or access mode (via the command “switchport mode trunk” or “switchport mode access”) but in fact DTP is still running in these modes. Please read at http://packetlife.net/blog/2008/sep/30/disabling-dynamic-trunking-protocol-dtp/. The only way to disable DTP on a switch port is to use the “switchport nonegotiate” command. But notice this command can only be used after configuring that switch port in “trunk” or “access” mode.

Therefore this is a question with no correct answer but if we have to choose an answer, we will choose answer A. At least it is correct in theory.

Question 3

Question 4

Explanation

The Dynamic Trunking Protocol (DTP) is used to negotiate forming a trunk between two Cisco devices.

In fact this question is unclear as it does not ask about a specific switch model. The default DTP configuration for Cisco Catalyst 2960 and 3560 switches is dynamic auto while older 3550 switches run Dynamic Desirable as the default mode. So in this question we should follow the “newer” switches (which is “dynamic auto” mode).

New switches are only set to “dynamic auto” mode by default so they are safer as they do not try to form a trunk aggressively.

Therefore in this question “dynamic auto” is the best choice.

Reference: http://www.ciscopress.com/articles/article.asp?p=2181837&seqNum=8

Comments (21) Comments
  1. so??
    April 18th, 2017

    Is the answer to question 2
    trunk or access?
    (i am not able to see the questions currently)

  2. Anonymous
    June 7th, 2017

    in regards to Q 1, I thought CDP, DTP traveled on the native VLAN.
    Because if ‘Control traffic like CDP, DTP, PAgP, and VTP uses VLAN 1 to operate, even if you change the native VLAN.’ is true. When you shut VLAN 1 would you no longer see CDP neigh??

  3. Anonymous
    June 14th, 2017

    So Maria,

    Were the 9tut dumps any use to you?

  4. Pete
    June 18th, 2017

    Is question 1 not Native Vlan??

  5. @Anonymous
    July 2nd, 2017

    you can’t shutdown vlan 1 or suspend

  6. Joe
    July 8th, 2017

    But you can prune vlan 1 from a trunk; in which case I’m pretty sure cdp still works. I’ll have to research.

  7. no
    July 29th, 2017

    No, only VLAN0001 for control traffic, no matter what you do, including pruning with VTP, according to this at least:

    https://supportforums.cisco.com/discussion/10790041/shutting-down-vlan1-security-switchport-trunk-native

  8. KR
    August 9th, 2017

    For question 4, option D (Dynamic Auto) is correct for Catalyst 2960 and 3560 but option C (Dynamic desirable) is correct for older Catalyst 2950 and 3550 switches as stated in the link provided under question 4 explanation. The question states “Whats DTP’s default in a switch?”. How can option D be correct when we dont know which series switch it is?

  9. Almost there :)
    August 9th, 2017

    Anyone done the exam lately?
    I have mine next friday

  10. ICND2
    August 9th, 2017

    Hi,
    for question 2 I have found this
    https://supportforums.cisco.com/discussion/12915416/change-dynamic-auto-access-mode-will-disable-dtp-effectively

    my understanding is that the correct answer is D.

    If configured as trunk you need also the command switchport nonegotiate. Any thought on this?

  11. kksmh
    August 17th, 2017

    I had question 4 modified today on icnd2 the choices were:
    What is DTP’s default in a switch?
    A. ON
    B. OFF
    C. Desirable
    D. Auto

    Is it Auto or ON?

  12. Big Gun
    August 28th, 2017

    @kksmh

    DTP default mode?

    Older devices were auto, newer devices are desirable. Cisco changed this to make it a bit more secure. I would go with desirable as the correct answer.

  13. ConfigGuru
    September 14th, 2017

    Is anyone having troubles seeing the questions

  14. DL
    October 3rd, 2017

    Question 2’s answer is D. When you configure the interface in Access mode it stops negotiating the trunk (show interface switchport), even if some DTP packets are still being sent by the interface.

  15. Anonymous
    October 19th, 2017

    se repiten las preguntas 1 con la 5.. por que?

  16. LF
    October 19th, 2017

    se repiten las preguntas 1 con la 5.. por que?

  17. FB
    November 11th, 2017

    I would definitely go for answer D on question 2 – putting the interface into switchport mode access will stop DTP

  18. EAGLE_EYE
    November 14th, 2017

    Q2. How can you disable DTP on a switch port?

    Switchport Mode Access: This puts the interface (ACCESS PORT) into a PERMANENT NON-TRUNKING mode and negotiates to convert the link into a NON-TRUNK link. The port would be a dedicated Layer 2 access port!

    Switchport Nonegotiates: Prevents the interface from generating DTP Frames. You can use this command only when the interface switchport mode is (ACCESS/TRUNK).

  19. Johnny
    November 24th, 2017
  20. RnS Newbie
    December 1st, 2017

    Q4 and Q7 (default mode for DTP) counteract each other. Please clarify, and remove the question that reflects the wrong answer.
    For what it’s worth, my research indicates the DTP default can change based on the type of switch you are using. For a Cisco IOS switch: “By default, a Cisco Ethernet port’s default DTP mode is “dynamic desirable”, which allows the port to actively attempt to convert the link into a trunk.” — probably the best answer for current testing. (Note: For a Cisco ILS switch, the default is Auto.)

    As far as disabling DTP, I found this information:
    nonegotiate = Sets Trunking on and disables DTP. These will only become Trunks with ports in on or nonegotiate mode.
    off = This option sets Trunking and DTP capabilities off. This is usually the recommended setting for any access port since it prevents any dynamic establishments of Trunk links.

    Info found here: https://www.cisco.com/c/en/us/td/docs/net_mgmt/ciscoworks_lan_management_solution/4-2/user/guide/configuration/config/configvlan.html?dtid=osscdc000283

  21. CcNa
    December 12th, 2017

    Skunks