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ICND2 – EtherChannel Questions

October 29th, 2017 in ICND2 200-105 Go to comments

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Question 1

[am4show have=’p2;’]Refer to the exhibit. While troubleshooting a switch, you executed the “show interface port-channel 1 etherchannel” command and it returned this output. Which information is provided by the Load value?

Etherchannel_show_interface_port-channel.jpg

A. the percentage of use of the link
B. the preference of the link
C. the session count of the link
D. the number source-destination pairs on the link

 

Answer: D[/am4show]

Explanation

The way EtherChannel load balancing works is that the switch assigns a hash result from 0-7 based on the configured hash method ( load balancing algorithm ) for the type of traffic. This hash result is commonly called as Result Bundle Hash (RBH).

Now we need to convert Load value from Hexadecimal to Binary numbers. Therefore:
+ Gi1/1: 36 (Hex) = ‭00110110‬ (Bin) -> Bits 1, 2, 4, 5 are chosen (read from right to left, start from 0)
+ Gi1/2: 84 (Hex) = ‭10000100‬ (Bin) -> Bits 2, 7 are chosen
+ Gi1/3: 16 (Hex) = ‭00010110‬ (Bin) -> Bits 1, 2, 4 are chosen

Therefore if the RBH is 5, it will choose Gi1/1. If RBH is 4, it will choose Gi1/1 and Gi1/3 interfaces. If RBH is 2 it will choose all three above interfaces. And the bit sharing ratio is 3:3:2 (from “No of bits” column) hence two links has higher probability of getting utilized as compared to the third link.

Question 2

[am4show have=’p2;’]Which two actions must you take to configure a PAgP EtherChannel between two switches, S1 and S2? (Choose two)

A. Configure the channel-group 1 mode auto command on S1.
B. Configure the channel-group 1 mode desirable command on S2.
C. Configure the channel-group 1 mode active command on S2.
D. Configure the channel-group 1 mode on command on S2.
E. Configure the channel-group 1 mode active command on S1.

 

Answer: A B[/am4show]

Explanation

In PAgP we only have two modes: auto and desirable.

Comments (11) Comments
  1. zahir
    August 10th, 2017

    need more questions please.

  2. Kenno
    November 10th, 2017

    Thanks Archie, that’s bloody wonderful. I’ll never forget you or your upload 🙂

  3. MN
    February 22nd, 2018

    [spam_suspect]@9tut
    Math for Question 1 is not right! value should read from right to left as 76543210
    Therefore: it should be:
    + Gi1/1: 36 (Hex 3 and 6) = ‭0011 0110‬ (Bin) -> Bits 1, 2, 4, 5 are chosen
    + Gi1/2: 84 (Hex 8 and 4) = ‭1000 0100‬ (Bin) -> Bits 2, 7 are chosen
    + Gi1/3: 16 (Hex 1 and 6) = ‭0001 0110‬ (Bin) -> Bits 1, 2, 4 are chosen

    more detail
    http://packetpushers.net/understand-etherchannel-load-balancing-catalyst-switches/

  4. MN
    February 22nd, 2018

    @9tut
    Math for Question 1 is not right! value should read from right to left as 76543210
    Therefore: it should be:
    + Gi1/1: 36 (Hex 3 and 6) = ‭0011 0110‬ (Bin) -> Bits 1, 2, 4, 5 are chosen
    + Gi1/2: 84 (Hex 8 and 4) = ‭1000 0100‬ (Bin) -> Bits 2, 7 are chosen
    + Gi1/3: 16 (Hex 1 and 6) = ‭0001 0110‬ (Bin) -> Bits 1, 2, 4 are chosen

    more detail
    packetpushers.net/understand-etherchannel-load-balancing-catalyst-switches/

  5. 9tut
    February 23rd, 2018

    @MN: Thanks for your information, we have just updated the explanation of this question!

  6. Biggerstaff
    March 30th, 2018

    Good stuff!

  7. Satchmo
    July 16th, 2018

    Yes, more questions, thanks.

  8. Rick Springfield
    August 1st, 2018

    Q2 “In PAgP we only have two modes: auto and desirable.” PAgP has Auto, Desirable and On. On/On works, Desirable/Auto & Desirable/Desirable works – A & B are correct.

  9. marknie
    December 8th, 2018

    Thanx MN. Entire thing was fuzzy at first, making distinction between 2 to the 0 power is 1 vs. 0 is the first bit, you know? thanks

  10. albertopassedicnd2
    November 9th, 2019

    I passed ICND2 on November 4th with 854! There are 54 questions, 4 drag and drop 2 labs for me EIGRP and GRE, BGP, ACL, IP SLA, RSTP, HSRP, PPPOE Questions! I have all the labs, and the majority of the questions, I have two courses and a lot of labs from CISCO and UDEMY to be prepare write alberthdr AT hotmail point com

  11. Anonymous
    November 12th, 2019

    Scam!
    He will beg for money! Files incomplete!