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VLAN Questions

November 24th, 2019 in SWITCH 300-115 Go to comments

Question 1

Explanation

The Port Fast feature is automatically enabled when voice VLAN is configured. When you disable voice VLAN, the Port Fast feature is not automatically disabled.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12-1_19_ea1/configuration/guide/3550scg/swvoip.html

Question 2

Explanation

802.1Q VLAN frames are distinguished from ordinary Ethernet frames by the insertion of a 4-byte VLAN tag into the Ethernet header.

802.1q_header.png

Question 3

Explanation

Because the 802.1Q tunneling feature increases the frame size by 4 bytes when the metro tag is added, you must configure all switches in the service-provider network to be able to process maximum frames by increasing the switch system MTU size to at least 1504 bytes.

Question 4

Explanation

The VLAN ID field inside an 802.1q frame consists of 12 bits. Therefore we have 212 = 4096 VLAN IDs, theoretically.

802.1q_header.png

Question 5

Explanation

Each access port can be only assigned to one VLAN via the “switchport access vlan ” command.

Question 6

Explanation

This command is used to enable tagging of native VLAN frames on all 802.1Q trunk ports.

Answer A is not correct because even when the native VLAN is set to 1, all of the frames of the native VLAN are tagged.

Answer B is not correct because the control traffic still passes via the default VLAN (VLAN 1).

Answer C is not correct because all the frames are tagged with 4-byte dot1Q tag.

Answer D is not correct as “Control traffic continues to be accepted as untagged on the native VLAN on a trunked port, even when the vlan dot1q tag native command is enabled” according to this link: https://www.cisco.com/c/m/en_us/techdoc/dc/reference/cli/nxos/commands/l2/vlan-dot1q-tag-native.html

Question 7

Explanation

When you delete a VLAN, any LAN ports configured as access ports assigned to that VLAN become inactive. The ports remain associated with the VLAN (and inactive) until you assign them to a new VLAN.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/vlans.html

Question 8

Explanation

The PortFast feature is automatically enabled when voice VLAN is configured. When you disable voice VLAN, the PortFast feature is not automatically disabled.

Question 9

Question 10

Comments
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  1. Anonymous
    June 10th, 2018

    Q15:

    No VTP protocol is specified, then shouldn’t the answer be A-E?
    Others are not valid due to incorrect range.

  2. CCNA-AZ
    July 25th, 2018

    Question 6:
    I think the answer here is A (May be I am wrong as I am not a Cisco expert)

    Since Control traffic always use VLAN 1 (regardless it is native or not) and stay untagged (I can not find any resource telling that “In these circumstances Control traffic will be tagged”), “vlan dot1q tag native” command will not tag control traffic inside VLAN 1. On the other hand, if native VLAN is not vlan 1, for example, VLAN 20, then all traffic inside the VLAN 20 will be tagged. Here Control traffic will still use VLAN 1.

  3. Dany1
    July 27th, 2018

    Question 6: Answer is D. Control traffic is tagged (GOOD).
    “Control traffic continues to be ACCEPTED as untagged on the native VLAN on a trunked port, even when the vlan dot1q tag native command is enabled.”
    In that document, CISCO talk about INGRESS TRAFIC.
    On GNS3 put that scenario : two switches, SW1 without “vlan dot1q tag native” activated, SW2 with “vlan dot1q tag native” . Link between them is trunk ( ON or DTP), start WIreSHARK.
    On both switches define switchport trunk native vlan 99
    Results:
    1. SW2 will ACCEPT UNtagged trafic form VLAN 99 ( example configure spanning-tree vlan 99 priority 20579 on SW1; SW1 will become root bridge), but SEND traffic for VLAN 99, tagged
    2. SW1 will accept tagged trafic for NATIVE VLAN
    3. SW1 interface is defined switchport trunk native vlan 99 and switchport mode dynamic desirable: DTP send by SW1 is send as IEEE 802.3 Ethernet frame
    SW2 is defined switchport trunk native vlan 99(default mode dynamic auto) and send DTP frame as 802.1 Q VLAN 99. DTP Control_TR status UP
    So, in summary: reference document indicated by Anonymous talk about INCOMING, INGRESS TRAFIC. Answer D for Question 6 is perfect.

  4. Dany1
    July 27th, 2018

    For CCNA-AZ:
    1. Native VLAN means that this VLAN will be untagged when it’s used over the trunk-ports, by default this will be VLAN 1.
    If Native VLAN you changed from VLAN 1 to VLAN99, meaning that any traffic in VLAN99 will never be tagged on trunk-ports, but VLAN 1 will be tagged. VLAN 99 wil be tagged when you configure globally “vlan dot1q tag native”. Using that command at level global, will impact over all native vlans defined on all trunks in that switch (example: 10 trunks with native vlan 1,2,3,4,5,6,7,8,9,10 will be tagged frame for VLAN 1-trunk 1, VLAN2-trunk2 …). Native VLAN has local (at trunk level) significance.
    2. CDP, VTP, and PAgP updates are always forwarded on trunks with a VLAN 1 tag. This is the case even if VLAN 1 has been cleared from the trunks and is not the native VLAN
    Summary:
    if Native VLAN is XXX, control traffic send through VLAN 1 it is TAGGED with VLAN 1 tag, with or without “vlan dot1q native” command That command is handle ONLY native vlan, which is not tagged by default.

  5. Dany1
    July 27th, 2018

    Question 16:
    if the native VLAN is VLAN1 then:

    VLAN1 standard STP BPDU is sent untagged (eth.dst == 01:80:c2:00:00:00 Wireshark)
    VLAN1 PVST+ BPDU is sent untagged (eth.dst == 01:00:0c:cc:cc:cd Wireshark)
    Other VLAN’s PVST+ BPDUs are sent tagged with their appropriate VLAN (802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 10, eth.dst == 01:00:0c:cc:cc:cd )

    If the native VLAN is different from VLAN1 then:

    VLAN1 standard STP BPDU is sent untagged (eth.dst == 01:80:c2:00:00:00 Wireshark)
    VLAN1 PVST+ BPDU is sent tagged with VLAN1 (802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 1, eth.dst == 01:00:0c:cc:cc:cd )
    Other VLAN’s PVST+ BPDUs are sent tagged accordingly (the one for the native VLAN will be untagged)
    When native VLAN is tagged, every frame is tagged.
    Summary
    Answers:
    C. Normal STP VLAN 1 BPDU travel across VLAN 1 untagged ( more precisely “VLAN1 standard STP BPDU is sent untagged”)
    D. PVST+ VLAN 99 BPDU travel across VLAN 99 tagged (because of “native VLAN tagged”
    Check my answers with real switches or GNS3

  6. CCNA-AZ
    July 28th, 2018

    @Dany1

    Thanks a lot for your brief explanation.

  7. Angry Clown
    September 29th, 2018

    Hey guys, this question is bugging me…
    Question 5

    What is the maximum number of VLANs that can be assigned to an access switchport without a voice VLAN?
    A. 0
    B. 1
    C. 2
    D. 1024

    Answer: B
    Explanation
    Each access port can be only assigned to one VLAN via the “switchport access vlan ” command.

    Here it says only one vlan is allowed on an access port but on the quizes it says two which seems right, the voice vlan and data vlan. which one is the correct answer??? gggrrrr

  8. Remlin
    October 14th, 2018

    @Angry Clown

    It already states in the question with a voice vlan.

  9. Kazi
    January 24th, 2019

    Hi,
    Any body can help me the valid dump to kaziDOTshabbirDOTahmedATgmailDOTcom as I will sit for exam this week.Thanks in advance

  10. Anonymous
    March 11th, 2019

    yes

  11. Muhamad
    March 15th, 2019

    Pass on 13th march. My lab is HRSP and AAA dot1q. you should study them well.
    Few new questions, dump valid. Thanks certprepare!

    ====
    My email: muhamadawan1988(at)gmail(dot)com

  12. supportdonkey
    March 24th, 2019

    Muhamad is a fake! He just wants to sell dumps!

  13. elric
    March 30th, 2019

    Hi,
    Any body can help me the valid dump to dani_edi29 hotmail dot com as I will sit for exam this week.Thanks in advance!!

  14. NIC
    April 1st, 2019

    Did anybody get the answer for Q4? Isn´t it 32?

  15. NIC
    April 1st, 2019

    So, what is the answer for Q6?

  16. couldbe
    April 5th, 2019

    Use the vlan dot1q tag native global configuration command to configure the edge switch so that all packets going out an IEEE 802.1Q trunk, including the native VLAN, are tagged. Has to be used on IEEE 802.1Q Tunneling Port – QinQ.

  17. nahas
    April 29th, 2019

    Q7 states the after removing the vlan the interfaces go down until they are reassigned to a VLAN.
    I tried with GNS3 but I found that the port status remain up/up.
    After removing the vlan wih “no vlan x” command , I launched “show interfaces switchport” which displayed the vlan as inactive.
    “show vlan” dosen’t display anymore the vlan and the interface.
    “show ip interface brief” displays the port UP/UP.
    Does anyone know?

  18. mousti
    May 12th, 2019

    hi nahas
    this is true only in Nexus . in others platform the port in that vlan is inactive. show int X swichport>>>inactive

  19. darylchris
    May 20th, 2019

    Passed 300-115 yesterday, lab was AAA dot1q and HSRP sim and VTPv3 sim. I used IPHelper dump and its valid. My email : darylchris0511(at)gmail(dot)com

  20. Henry
    May 20th, 2019

    Q7 is weird
    The port WILL NOT go down, instead, it will just become “inactive”.
    “down” means no traffic at all. Well, I put a sniffer in the middle and I captured packets going back and forth.

  21. Henry
    June 2nd, 2019

    About Q6, choice is D is correct.
    Documents on internet don’t explain it properly. Here it is in plain English:
    When “vlan dot1q tag native” is setup on the local switch:
    – control traffic is SENT tagged (on vlan 1, you should already know this)
    – control traffic CAN BE RECEIVED tagged (the remote switch sends tagged control traffic on vlan 1) or untagged (the remote switch sends untagged control traffic on vlan 1)

  22. Super
    June 21st, 2019

    anyone have latest dumps? please send link

  23. MJxxx
    August 7th, 2019

    Q6 – D is correct.

    Very simple:
    Control traffic (=CDP, VTP, PAgP updates) is always sent via the native VLAN, which is by default VLAN 1.
    The native VLAN by default sends untagged traffic.

    You can change the native VLAN to be any other VLAN-X instead of VLAN 1, and remove VLAN1 from your trunk ports.
    You can also decide to tag the traffic on the native VLAN by setting the given command:
    “vlan dot1q tag native”

    -if you have done that, you have just tagged the control traffic which is sent over the native VLAN.

  24. Anonymous
    September 23rd, 2019

    where can i find these questions ??

  25. tom
    September 23rd, 2019

    go to SWITCH FAQs & Tips section. point 8

  26. Nick
    October 25th, 2019

    Question 7 is correct. I thought it was A at first glance. After you delete a VLAN with port assigned. Do a show interface xx switchport. Interface is inactive til it is reassigned.

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