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Switch Questions

January 24th, 2021 Go to comments

Quick review of switch function:

In brief, the basic switching function at Layer 2 adheres to these rules for determining forwarding responsibility:
+ If the destination MAC address is found in the CAM table, the switch sends the frame out the port that is associated with that destination MAC address in the CAM table. This process is called forwarding.
+ If the associated port to send the frame out is the same port that the frame originally came in on, there is no need to send the frame back out that same port, and the frame is ignored. This process is called filtering.
+ If the destination MAC address is not in the CAM table (that is, unknown unicast), the switch sends the frame out all other ports that are in the same VLAN as the received frame. This is called flooding. It does not flood the frame out the same port on which the frame was received.
+ If the destination MAC address of the received frame is the broadcast address (FFFF.FFFF.FFFF), the frame is sent out all ports that are in the same VLAN as the received frame. This is also called flooding. The only exception is the frame is not sent out the same port on which the frame was received.

Reference: http://www.ciscopress.com/articles/article.asp?p=2348264

Question 1

Question 2

Explanation

The down/down state indicates a Layer 1 problem -> “Protocol mismatch” answer is a Layer 2 problem so it is not correct.

Duplex should be matched on both side but it is not a must -> Therefore “duplex mismatch” is not a correct answer.

The most common Layer 1 problems are faulty or incorrect cabling or hardware failure but none of them is in the answer choices.

If the port is error-disabled, we will see it in down/down state so this answer is correct.

SW#sh int f1/0/1
FastEthernet1/0/1 is down, line protocol is down (err-disabled)

There are only two answers left, which are “speed mismatch” and “interface is shut down”. According to the table below (from the old and retired ICND1 100-101 Official Cert Guide), speed mismatch is also a cause of down/down state.

interface_status.jpg

Note:
+ Speed must match between two ends. We tested speed mismatch on real device but we only received “up/down” state.
+ If “interface is shut down” then we will see the “administratively down/down”, not “down/down” state. But the “down/down” state would be seen on the far end interface.

Question 3

Question 4

Explanation

The MAC addresses in the CAM table are the source MAC addresses only. Therefore it only learns MAC address from ingress traffic.

Comments (16) Comments
  1. Anonymous
    January 23rd, 2021

    @9tut,
    Can you explain answer C (C. moves packets within a VLAN) of Question 3, please?
    I thought VLANs are at layer3 and the question is referring at layer 2 switch!! Thanks a lot.

  2. Anonymous
    February 1st, 2021

    VLANS are on L2 like the Ethernet protocol and these protocols are:

    https://www.manageengine.com/network-monitoring/layer-2-protocols.html

  3. micheale
    February 10th, 2021

    anyone who have …….readable book for CCNA 200-301

  4. HIRO
    July 1st, 2021

    The SW1 interface g0/1 is in the down/down state. Which two configurations are valid reasons for the interface conditions? (Choose two)
    A. There is a duplex mismatch
    B. There is a speed mismatch
    C. There is a protocol mismatch
    D. The interface is shut down
    E. The interface is error-disabled

    I think about the problem
    answer is B and E

  5. Alfie
    July 26th, 2021

    Question 2
    B and E are the right answers

  6. 9tut
    July 26th, 2021

    @HIRO, @Alfie: Yes, thanks for your detection! We reviewed Q2 and corrected them.

  7. ZA93
    July 29th, 2021

    Hi, regarding Question 2 :
    The SW1 interface g0/1 is in the down/down state. Which two configurations are valid reasons for the interface conditions? (Choose two)
    A. There is a duplex mismatch
    B. There is a speed mismatch
    C. There is a protocol mismatch
    D. The interface is shut down
    E. The interface is error-disabled

    we can understand it better on the CLI :

    Router#show ip int br
    Interface IP-Address OK? Method Status Protocol
    GigabitEthernet0/0/0 10.2.2.2 YES manual up up
    GigabitEthernet0/0/1 unassigned YES unset administratively down down
    GigabitEthernet0/0/2 unassigned YES unset administratively down down
    Vlan1 unassigned YES unset administratively down down
    Router#

  8. Jason
    February 14th, 2022

    Thanks,

  9. Shah Mohammad Niazy
    February 15th, 2022

    how to wipe the switch in easy way?

  10. bobo
    April 19th, 2022

    Shah Mohammad Niazy – you do a “write erase” (takes out config file)then make sure your in flash directory and do a “delete vlan.dat” (takes out vlan database/CAM)

  11. Anonymous
    November 1st, 2022

    I am not able to see the question, I have paid for the premium service, could you please fix this issue as soon as posible

  12. 9tut
    November 1st, 2022

    @Anonymous: If your problem still exists, please send an email to support@9tut.com.

  13. Arsalan
    December 21st, 2022

    Hi guys! Please tell me, If i’m from Russia can I get Cisco certificate?

  14. Anonymous
    March 23rd, 2023

    Hi guys! I’m from somalia how can I learn cisco for my language?

  15. D
    January 25th, 2024

    @9tut what does mean by speed mismatch in Question 2?? Does it mean port speed??

  16. 9tut
    January 26th, 2024

    @D: Speed means 10Mbps, 100Mbps or 1000Mbps. You can find the speed of the interface with the “show interfaces” (for example: “Full duplex, 100Mb/s”) or “show interface {interface} status”.

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