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VLAN Questions

November 19th, 2018 Go to comments

Note: If you are not sure about Virtual Local Area Network (VLAN), please read our Virtual Local Area Network VLAN Tutorial.

Quick summary about VLAN:

Be default all access ports belong to VLAN 1. If we want to assign a new VLAN, we have to use the command “switchport access vlan <vlan-id>” under interface mode.

VLAN Benefits:

– Logically group devices by department/function, not location so it provides more efficient use of bandwidth
– Separate broadcast domains, thus reducing their sizes and help mitigate broadcast storms
– Provide additional security because it separates sensitive data traffic from other traffic

The following commands are used to a create a VLAN (for example VLAN 10) and assign it to an interface (for example fa0/1) on a switch:

Switch(config)#vlan 10 //Create VLAN 10 first
Switch(config)#interface fa0/1
Switch(config-if)#switchport access vlan 10 //assign Fa0/1 interface to VLAN 10

To verify a VLAN or check which ports belong to which VLAN, use the “show vlan” command (or “show vlan id <vlan-id>” for a specific VLAN)

Question 1

Question 2

Question 3

Question 4

Question 5

Explanation

On an Ethernet connection, a duplex mismatch is a condition where two connected devices operate in different duplex modes, that is, one operates in half duplex while the other one operates in full duplex. Duplex mismatch can easily cause collision domain issue as the device that operates in full duplex mode turns off CSMA/CD. So it is eager to send data immediately without checking if the link is free to use -> A is correct.

An “inband path” is the path which provides path for management traffic (like CDP, VTP, PAgP…) but we are not sure why congestion on the switch inband path can cause collision domain issues. Maybe congestion on inband path prevents the JAM signal (sent when a collision occurs on the link) to be sent correctly on the link.

Question 6

Explanation

If we configure an access port as follows:

Switch(config)#interface fa0/1
Switch(config-if)#switchport mode access

Then this interface, by default, will belong to VLAN 1. Of course we can assign another VLAN to this port via the “switchport access vlan {vlan-number}” command.

Question 7

Explanation

Traffic on the native VLAN is untagged -> Answer B is not correct.

Control plane traffic (like CDP, VTP, STP…) runs on VLAN 1 by default. They are not blocked on the native VLAN -> Answer C is not correct.

If the answer says “the native VLAN should be set so that no real traffic running on it for security reasons” then it is correct but the native VLAN is not typically disabled -> Answer D is not correct.

CDP runs on VLAN 1 by default and the native VLAN is also VLAN 1 by default so answer A is the best choice here.

Question 8

Explanation

With the configuration above, when we type “do show vlan” we would not see VLAN 10 in the VLAN database because it has not been created yet. VLAN 10 is only created when we exits VLAN configuration mode (with “exit” command).

Question 9

Explanation

IEEE 802.1Q is the networking standard that supports virtual LANs (VLANs) on an Ethernet network. When a frame enters the VLAN-aware portion of the network (a trunk link, for example), a VLAN ID tag is added to represent the VLAN membership of that frame. The picture below shows how VLAN tag is added and removed while going through the network.

VLAN_tag_added_removed.jpg

Question 10

Explanation

When using VLAN the number and size of collision domains remain the same -> A is not correct.

VLANs allow to group users by function, not by location or geography -> B is correct.

VLANs help minimize the incorrect configuration of VLANs so it enhances the security of the network -> C is correct.

VLAN increases the size of broadcast domains but does not decrease the number of collision domains -> D is not correct.

VLANs increase the number of broadcast domains while decreasing the size of the broadcast domains which increase the utilization of the links. It is also a big advantage of VLAN -> E is correct.

VLANs are useful but they are more complex and need more administration -> F is not correct.

Comments (23) Comments
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  1. B
    June 1st, 2018

    9tut, you should allow Comments under each question (so users would be able to discuss) and hide the answers, explanations and comments by default.

  2. Ow_youtube
    June 22nd, 2018

    About VLAN, there is a nice video on youtube..enjoy
    https://www.youtube.com/watch?v=z9OIGwzgs54&t=78s

  3. Mo”
    June 25th, 2018

    Hi

    Can anyone tell me , why I am not seeing questions and answers but just seeing only explanations

    Thanks.

  4. blabla
    July 27th, 2018

    I think question 8 is wrong. If you type (config)#vlan 10, vlan is already created. I do not have real switch to check this but im almost sure i saw topic about that in cisco book.
    In packet tracer it works as i said.

  5. NAN
    August 9th, 2018

    I passed the exam. I only looked at the contents of it. Most of the questions are in it. It is worthy of trust.

    http: / / t.cn/RDf8DJW

  6. Anand
    August 29th, 2018

    These are the answers. where are the questions ?

  7. jay
    September 22nd, 2018

    guys how can i see the answers without questions??? how ???

  8. venki
    September 26th, 2018

    For question 5 packet tracer adds vlan 20 as soon as when u enter VLAN 20 command…but in a real router it doesn’t work… vlan added only when u exit from VLAN config mode …try it on GNS3…

  9. hoi
    September 28th, 2018

    Q5 Answer D is not correct. There are no collisions on a failing NIC.

  10. Baker
    November 3rd, 2018

    Where are the questions????

  11. zamil
    November 3rd, 2018

    Q 2

    Switch#sh vlan id 20

    VLAN Name Status Ports
    —- ——————————– ——— ——————————-
    20 VLAN0020 active Fa0/2, Fa0/8, Fa0/10, Fa0/13
    Fa0/14

  12. rian
    November 9th, 2018

    anyone can help me the purpose of NAtive VLAN?…purpose of etherchannel?
    please need your idea as soon as possiblle..Thanks advance

  13. Amir
    November 26th, 2018

    #9tut Staff
    Hey guys!
    This is the second time I’m encountering with a bug on your quizzes interface,
    Please pay attention to this problem, the correct answers are not always displayed correctly.
    Here’s an example showing the review portion of the quiz, I chose the correct answer and it still shows a different correct answer with the content:
    [IMG]http://i66.tinypic.com/fcmx44.jpg[/IMG]

  14. 9tut
    November 26th, 2018

    @Amir: Thanks for your information. We will try to fix the issue.

  15. william
    December 12th, 2018

    Can anyone share the latest CCNA dumps at bullscashonline18 att gmail dot com
    That would be really helpful!!!

    I am going to sit for exam in the last of this exam…
    i will be really thankful to guys,,,,,

  16. Haidar
    June 24th, 2019

    I can’t see the question 1-5

  17. zuhud
    August 5th, 2019

    Q5 answer is incorrect. It should be A and E. In the same VLAN the two most common causes of collision issues are duplex mismatch then overloaded segment. In fact failing NIC is also the next to look at esp if more than one collision domain experiencing problems.

    Question 5

    Which two circumstances can cause collision domain issues on VLAN domain? (Choose two)
    A. duplex mismatches on Ethernet segments in the same VLAN
    B. multiple errors on switchport interfaces
    C. congestion on the switch inband path
    D. a failing NIC in an end device
    E. an overloaded shared segment

    Answer: A C

  18. Anonymous
    August 11th, 2019

    why questions doesn’t appear?

  19. Abdiel
    September 23rd, 2019

    Hey BlaBla!! I just proved what you said in a real switch an actually the switch does not create the vlan untill you exit global configuration mode, true story 100% real no fake

  20. Rony
    September 26th, 2019

    Hello, can any one tell me how I can see the question or where I can ge it?

    Thanks

  21. Neil
    November 12th, 2019

    Q5. Right answers, A and D.

    If users on different collision domains (but in the same VLAN) are having the same performance issues, it still may be caused by a duplex mismatch on one or more Ethernet segments between the source and destination. The following scenario often happens: a switch is configured manually to have full-duplex on all ports in the VLAN (the default setting is “auto”), while users (network interface cards [NICs]) connected to the ports are performing an auto-negotiation procedure. This results in duplex mismatch on all ports and, therefore, bad performance on each port (collision domain).
    Another case to be considered is a particular NIC performance problem. If a NIC with a performance problem is connected to a shared segment, then it may appear that a whole segment is experiencing slowness, especially if the NIC belongs to a server that also serves other segments or VLANs. Keep this case in mind because it may mislead you as you troubleshoot.

    https://www.cisco.com/c/en/us/support/docs/lan-switching/virtual-lans-vlan-trunking-protocol-vlans-vtp/23637-slow-int-vlan-connect.html

  22. Toni
    November 17th, 2019

    Hi @9tut, would you please comment the above – about Q5.
    Thank you

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