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VLAN Trunking 2

September 16th, 2017 in SWITCH 300-115 Go to comments

Question 1


The 802.1q frame format is same as 802.3. The only change is the addition of 4 bytes (32 bits) fields. That additional header includes a field with which to identify the VLAN number. Because inserting this header changes the frame, 802.1Q encapsulation forces a recalculation of the original FCS field in the Ethernet trailer.

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9


The “switchport mode trunk” is the most important command to identify if a port is configured in access or trunk mode. In this case because of the “switchport mode trunk” command, the “switchport access vlan 700” does not have any effect.

There is no “switchport trunk native vlan …” command so it is using the default native VLAN, which is 1.

  1. mikeSWE
    July 19th, 2017

    @certprepare URGENT exam in 2 days!!!

    I have dumps that have different answers on q5 (AC) q11 (D) and q12 (DF)

    Those are the correct answers in my dump brand new dump btw.

    Can someone please confirm if the answer here on these questions are the correct answers?

  2. BoZZ
    August 13th, 2017

    Question 6 – answer should be A and C. Trunks never add or remove tags. Access and voice vlan config does.

    Question 11 – answer B is correct, “tag native” causes all vlans to get tagged, even from native vlan which is not tagged by default.
    https:// supportforums.cisco.com /discussion/11823136/native-vlan-tagging

    Question 12 – C and D are correct.
    “the main enhancement introduced by MST is that several VLANs can be mapped to a single spanning tree instance.”
    https:// http://www.cisco.com /c/en/us/support/docs/lan-switching/spanning-tree-protocol/24248-147.html#mst_region

  3. BoZZ
    August 14th, 2017

    Question 13 – Answer is C. “show interface trunk” shows trunk ports after the trunk is established (not when port is made a trunk port), which is possible when other side is also configured correctly.

  4. Peter Pan
    August 20th, 2017

    Q5. Which 2 are the correct answers ?

    All 3 seem correct.

  5. Anonymous
    September 9th, 2017

    Would love some updates on this page for the previous users questions.

  6. f
    October 2nd, 2017

    whats is the difrent between q4 and q8 ?

    • remove VLAN 100 from the allowed VLAN lis:
    o switchport trunk allowed vlan remove vlan 100
    o switchport trunk allowed vlan 1-80,99,101-250

    • two commands are used to remove VLAN 55 from the trunk port:
    o switchport trunk allowed vlan remove 55
    o switchport trunk allowed vlan except 55

    can some one explain please ?

  7. Anonymous
    October 12th, 2017

    Here is the complete command with options.

    Switch(config-if)# switchport trunk allowed vlan { vlan-list | all |
    { add | except | remove } vlan-list }

    You can tailor the list of allowed VLANs on the trunk by using the switchport trunk
    allowed vlan command with one of the following:
    ■ vlan-list: An explicit list of VLAN numbers, separated by commas or dashes.

    ■ all: All active VLANs (1 to 4094) will be allowed.

    ■ add vlan-list : A list of VLAN numbers will be added to the already configured list;
    this is a shortcut to keep from typing a long list of numbers.

    ■ except vlan-list : All VLANs (1 to 4094) will be allowed, except for the VLAN numbers
    listed; this is a shortcut to keep from typing a long list of numbers.

    ■ remove vlan-list : A list of VLAN numbers will be removed from the already configured
    list; this is a shortcut to keep from typing a long list of numbers.

  8. Anonymous
    October 12th, 2017

    c3550#configure terminal
    Enter configuration commands, one per line. End with CNTL/Z.
    c3550(config)#int fa0/2
    c3550(config-if)#switchport trunk encapsulation dot1q
    c3550(config-if)#switchport mode trunk
    c3550(config-if)#switchport trunk allowed vlan remove 5-10,12
    c3550(config-if)#switchport trunk allowed vlan add 7
    c3550#show interfaces fastEthernet 0/2 trunk

    Port Mode Encapsulation Status Native vlan
    Fa0/2 on 802.1q trunking 1

    Port Vlans allowed on trunk
    Fa0/2 1-4,7,11,13-4094

    Port Vlans allowed and active in management domain
    Fa0/2 1

    Port Vlans in spanning tree forwarding state and not pruned
    Fa0/2 1

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