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EtherChannel Questions

May 16th, 2017 Go to comments

If you are not sure about EtherChannel, please read our EtherChannel tutorial.

Question 1


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 3, 4, 6, 7 are chosen
+ Gi1/2: 84 (Hex) = ‭10000100‬ (Bin) -> Bits 1, 6 are chosen
+ Gi1/3: 16 (Hex) = ‭00010110‬ (Bin) -> Bits 4, 6, 7 are chosen

Therefore if the RBH is 3, it will choose Gi1/1. If RBH is 4, it will choose Gi1/1 and Gi1/3 interfaces. If RBH is 6 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


EtherChannel misconfiguration occurs when the channel parameters do not match on both sides of the EtherChannel, resulting in the following message:

%PM-SP-4-ERR_DISABLE: channel-misconfig error detected on Po3, putting E1/3 in err-disable state

Therefore from the output above we can see that when miconfigured, the physical (member) interface is put into err-disable state.

But this question asks above “the status of port-channel” (not the physical member interface) so answer “Disabled” is a better choice.

Question 3


All interfaces in an EtherChannel must be configured identically to form an EtherChannel. Specific settings that must be identical include:
+ Speed settings
+ Duplex settings
+ STP settings
+ VLAN membership (for access ports)
+ Native VLAN (for trunk ports)
+ Allowed VLANs (for trunk ports)
+ Trunking Encapsulation (ISL or 802.1Q, for trunk ports)

Question 4


LACP is the IEEE Standard (IEEE 802.3ad) and is the most common dynamic Etherchannel protocol, whereas PAgP is a Cisco proprietary protocol and works only between supported vendors and Cisco devices.

Question 5


There are two PAgP modes:

Auto Responds to PAgP messages but does not aggressively negotiate a PAgP EtherChannel. A channel is formed only if the port on the other end is set to Desirable. This is the default mode.
Desirable Port actively negotiates channeling status with the interface on the other end of the link. A channel is formed if the other side is Auto or Desirable.

The table below lists if an EtherChannel will be formed or not for PAgP:

PAgP Desirable Auto
Desirable Yes Yes
Auto Yes No
Comments (15) Comments
  1. Tomorrow Exam
    April 10th, 2017

    What is the status of port-channel if LACP is misconfigured?

    A. Forwarding
    B. Enabled
    C. Disabled
    D. Errdisabled

    Hi can you please explain why C is the answer and not D

  2. Abdullah
    April 10th, 2017

    @Tomorrow Exam the answer is C which is Disabled

  3. Dude
    April 13th, 2017

    @9Tut what is the correct answer for 4th question is it Disabled state or Errordisabled state.

  4. jabs
    May 8th, 2017

    Torrow exams, the Errdisabled is a port-security violation state, which you will get when you configure port security with security violation on a switchport.. The etherchannel port will be disabled if the parameters of LACP configuration are not met at both ends.. Exam when bot end of the link are configure with passive, the LACP link is disabled.. so we have port status in LACP as diasbled, Passive, Active en on. where on-on will active the link, Active-passive will activate the link .

  5. San
    May 24th, 2017

    Can someone explain this

    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?

    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

  6. Anonymous
    June 3rd, 2017

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  7. ram
    June 8th, 2017

    i cant see the questions

  8. Anonymous
    July 17th, 2017

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  9. Anonymous
    July 30th, 2017

    when troubleshooting ethernet connectivity issues how can you verify that an ip address is known to a router? Plz any one can answer

  10. Anonymous
    July 30th, 2017

    what is the matric for the route from R1 to ? Plz any one can answer me

  11. Anonymous
    July 30th, 2017

    when running ospf what would cause router A note to form an adjacency with router B? Need ans plzz

  12. Anonymous
    July 30th, 2017

    which configuration can be used with pat to allow multiple inside address? Any one can give me ans

  13. Preeti
    September 21st, 2017

    New Ques. which command enable neighbor discovery in multi vendor environment?
    A. lldp transmit
    B. lldp receive
    C. cdp run
    D. lldp run
    Ans. D

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    October 6th, 2017

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  15. moatasem
    October 10th, 2017

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