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VLAN Trunking 3

November 24th, 2018 in SWITCH 300-115 Go to comments

Question 1

Explanation

The “vlan dot1q tag native” command maintains the tagging on the native VLAN and drop untagged traffic -> B is correct.

Reference: http://www.cisco.com/web/techdoc/dc/reference/cli/nxos/commands/l2/vlan_dot1Q_tag_native.html

Question 2

Explanation

Interface Gi5/1 is using 802.1q trunking which is an open standard protocol -> A is not correct while D is correct.

From the output we see the native VLAN of Gi5/1 interface is VLAN 1 so all untagged traffic should belong to VLAN 1 (using the default setting) -> B is not correct.

In this question we can only guess that “The device is configured with the default MST region” (also referred to as IST or Internal Spanning Tree). The “show interface trunk” command does not display any information about MST.

Answer E may be correct as interface Gi6/2 is in forwarding state for VLAN 36 so it may be the root port for VLAN 36.

So in conclusion there are two possibly correct answers but we have to choose one. We believe answer C is better than E so we choose it the best answer left.

Note: Answer F is not correct because VLAN 600 is the native VLAN on Gi6/2 does not mean untagged traffic is tagged with this VLAN. It only means “all untagged traffic belongs to VLAN 600”.

Question 3

Question 4

Explanation

From the summary in the book of “Cisco Press’ SWITCH Foundation Learning Guide”:

DTP_modes.png

We see an access port is formed when:

+ Both ports are in “Dynamic Auto”
+ One port in “Dynamic Auto” and the other port in “Access”
+ One port in “Dynamic Desirable” and the other port in “Access”
+ Both ports are in “Access”

Note: If you want to know what the result if one of the port is in “Nonegotiate” mode then this is the table you want:

DTP_modes_include_non_negotiate.jpg

Question 5

Question 6

Explanation

Although Gi0/10 has been configured as trunk it it did not appear in the “show interfaces trunk” command so the most suitable reason is it is down (not administratively down but down for another reason).

Question 7

Explanation

By entering the command “switch port trunk allowed vlan 2,3,4”, vlan 5 would be removed from allowed VLAN list. Both Workstations A & B are on VLAN 5 so they cannot communicate any more.

Note: If we want to add vlan 2 to 4 to the allowed VLAN list then we should use the “switchport trunk allowed vlan add 2,3,4”.

Question 8

Question 9

Question 10

Comments
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  1. Q3 clarification – Z-A-M
    June 12th, 2019

    Hello, does anyone have any further clarification on question 3 and the answer statements. It’s not really clear and we can interpret them in many ways … :(

  2. Q3 clarification – Z-A-M
    June 12th, 2019

    OK, i think the answer A should be “the link is down” so it take sense.

  3. Dmytro
    September 8th, 2019

    I think Q6 right answer is D.

  4. Q2
    September 16th, 2019

    any news on Q2
    are we still unsure of the answers?

  5. Dmytro
    September 25th, 2019

    About Q2, I think that right answers are:
    D. Interface Gi5/1 is using an industry standard trunking protocol
    F. On interface Gi6/2, all untagged traffic is tagged with VLAN 600

    F, because I think they mean exactly that untagged traffic is all traffic fron vlan 600.
    I don’t understand how we can check variants C or E, we don’t have any information about spanning-tree configuration.

  6. Q3 and Q6
    December 3rd, 2019

    What is the difference between Q3 and Q6. How can they be different answers?!?

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