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EtherChannel Questions 3

November 22nd, 2019 in SWITCH 300-115 Go to comments

Question 1

Explanation

From the outputs of the “show etherchannel summary” commands we learn that Switch1 is configuring EtherChannel with LACP while Switch2 is configuring with EtherChannel “on” mode -> the EtherChannel bundle does not go up.

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Explanation

You can determine if your port has been error disabled if you issue the “show interfaces” command.

cat6knative#show interfaces gigabitethernet 4/1 status
Port Name   Status       Vlan Duplex Speed Type
Gi4/1       err-disabled 100  full   1000  1000BaseSX

Reference: https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/69980-errdisable-recovery.html

Therefore we can check these attributes: VLAN, Duplex and Status. “Status” here can be considered the “port mode” (errdisabled mode) so in fact there are three correct answers in this case. But we should choose “VLAN” and “Duplex” which are obviously correct.

Question 8

Question 9

Explanation

By default, when an LACP channel is configured, the LACP channel mode is passive.

Reference: http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/19642-126.html

Question 10

Explanation

From the output above, we see the “Protocol” field is empty (with a “-” sign). Therefore we can conclude it does not run any EtherChannel protocol (mode “on”). This EtherChannel is up with “(SU)” keywords (“S” means “Layer 2” and “U” means “up”) -> This is an Layer 2 EtherChannel mode “on”.

Comments
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  1. QA
    July 10th, 2019

    Q6: From the switch foundation guide:

    If most of the traffic is IP, it makes sense to load balance according to IP addresses or port numbers. For non-IP traffic, the hash uses MAC addresses to calculate the path.

    So probably C is the ‘best’ answer as client/servers are involved e.g. for web, file, email based services and all IP based

    http://www.ciscopress.com/articles/article.asp?p=2348266&seqNum=3

  2. xor gates…
    September 15th, 2019

    XOR, or exclusive or, means 1XOR1 is not 1, it’s 0. hence the “exclusive” designation.

    just wanted to clear that up…

    the real answer should be src-dst mac, in my opinion (B) as it would increase the likelihood that flows from PC to SV1 would ride a different link than PC to SV2.

  3. Burìk
    November 3rd, 2019

    Q7

    “Therefore we can check these attributes: VLAN, Duplex and Status. “Status” here can be considered the “port mode” (errdisabled mode) so in fact there are three correct answers in this case. But we should choose “VLAN” and “Duplex” which are obviously correct.”

    That doesn’t sound right to me. Port status is one thing, port mode is another.

    Also:

    ——
    The compatibility check includes the following operational attributes:

    – Port mode
    – Access VLAN
    – Trunk native VLAN
    – Allowed VLAN list
    – Speed
    – 802.3x flow control setting
    – MTU

    https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/EtherChannel.html#85124
    —-

    It seems answers are A and E.

  4. AP
    November 19th, 2019

    Is this right answers ?

    Which two operational attributes can be checked for EtherChannel ports that are in err-disabled state? (Choose two)
    A. Port mode
    B. Port cost
    C. Duplex
    D. DTP
    E. VLAN

    Answer: C E

    Shouldn’t be A and C ?

  5. John2020
    January 23rd, 2020

    @certprepare

    Please help with Q6 ? is it D or A ?

    Thanks

  6. Q6 is just shit
    February 8th, 2020

    There is no context for Q6. assuming it is a L2 domain, and not L3, do they want to optimise for servers to client, or client to servers, or both. From which switch perspective, each is balancing the traffic in the opposite direction, so src and dst is effectively reversed. I would say the only sensible and general answer is B as it covers both directions.

    If they really want to know Server to client, then it is just Sw1 perspecive, you would want A, or B

    If it is Client to Servers, then it is from Switch 2 Perspective, and C or D, depending on if it is Layer 2 or Layer 3.

    In summary, Shit question, no way to know the correct answer. I wouldn’t choose any of those in production, I would use src and dst IP probably, if it was for both switches. Never know what else they will connect to in the future, and it is set system wide.

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