Home > EtherChannel Questions 4

EtherChannel Questions 4

September 12th, 2017 in SWITCH 300-115 Go to comments

Question 1

Explanation

For this question please remember this:

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

LACP Active Passive
Active Yes Yes
Passive Yes No

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

PAgP Desirable Auto
Desirable Yes Yes
Auto Yes No

To form an Etherchannel both sides must use the same Etherchannel protocol (LACP or PAgP). According the two tables above we can see only “desirable” and “auto” (of PAgP) can form an Etherchannel bundle.

Note: If we want to use “on” mode, both ends must be configured in this “on” mode to create an Etherchannel bundle.

Question 2

Question 3

Explanation

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

PAgP Desirable Auto
Desirable Yes Yes
Auto Yes No

Therefore we can see if one end is in “auto”, the other end must be in “desirable” mode to form an Etherchannel.

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Explanation

This question would be clear if we have the topology so we drew it here for your reference:

EtherChannel_Load_Balance_2.jpg

Destination MAC address is not correct as this is the MAC address of the server which is always fixed too.

Same for “source and destination MAC address”, it is not suitable either. In general we cannot use any MAC address for load balancing in this topology -> only source IP address is the best choice (as each “customer” has a different source IP address).

The “source MAC address” may be a correct answer as the traffic from R1 can go via one link while R2 can go via the other link if the hashes (using XOR algorithm) on these source MAC addresses are different.

But the option “source IP address” is the best choice here as there are many source IP addresses so the chance of load-balancing is better.

Comments
  1. CertPrep Nickname
    September 14th, 2017

    New section? Has the site PDF questions file been updated too?

  2. cahh
    October 23rd, 2017

    in Q.5, I think only E is correct, as option B (which is mode passive-passive) will not negotiate, right?

  3. mori
    October 29th, 2017

    in Q.5 , it asked for “2 command sequences” on 2 switches to negotiate.so “passive” and “active” mode is correct.

  4. switchy
    October 29th, 2017

    Q1 doesn’t have an image q_q

  5. Hank
    November 15th, 2017

    Q2???
    Is it asking for two, or one answer?
    To form an Etherchannel trunk, you do not have to set the allowed vlans. Vlans 1-1005 are automatically allowed. Therefore, it should be just answer D where it is absolutely necessary to configure a trunk.

  6. bigM
    November 24th, 2017

    Q5
    C+E

  7. bigM
    November 24th, 2017

    Q5 correction
    B & E

  8. Anonymous
    December 27th, 2017

    somebody please explain q4 and q6?

  9. john_padawan
    January 3rd, 2018

    @Anonymous December 27th, 2017
    -Q4
    In this question they are asking about load-balancing method based on Layer 3, so we can narrow down the options to IP protocol (Network Layer), therefore C and D are the only one correct.

    -Q6
    This is similar but here they are asking about load-balancing method based on Layer 2, so we can narrow down the options to MAC (Data Link Layer), therefore C and D are the only one correct.

  10. lalaversa
    May 4th, 2018

    Q8. The answers A & C seem to be obvious, but it IS NOT.
    SPAN source can be applied on an etherchannel … it is the SPAN destination that can not be applied on an etherchannel and in the question this is not specified.
    Only the answer C is surely correct but I think also the answer E is correct because ALL PORTS are in half-duplex and therefore allow to correctly establish the etherchannel connection (as if ALL PORTS were in full duplex).
    Usual pitfall question to make just so much confusion but the correct answers are C & E.

  11. patta
    May 23rd, 2018

    Q5 is very tricky, they don’t ask which two options will allow to form ether channel but in which modes port channel is capable of negotiation

    some info form cisco, links at the bottom:

    Passive—Places a port into a passive negotiating state, in which the port responds to LACP packets it receives but does not initiate LACP negotiation. In this mode, the port channel group attaches the interface to the bundle.

    auto—Places an interface into a passive negotiation state, in which the interface responds to PAgP packets that the interface receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets.

    on 3750’s

    TOP(config-if-range)#channel-group 1 mode ?
    active Enable LACP unconditionally
    auto Enable PAgP only if a PAgP device is detected
    desirable Enable PAgP unconditionally
    on Enable Etherchannel only
    passive Enable LACP only if a LACP device is detected

    both ends set to pagp auto:

    Flags: D – down P – bundled in port-channel
    I – stand-alone s – suspended
    H – Hot-standby (LACP only)
    R – Layer3 S – Layer2
    U – in use f – failed to allocate aggregator

    Group Port-channel Protocol Ports
    ——+————-+———–+———————————————–
    1 Po1(SD) PAgP Gi1/0/1(I) Gi1/0/2(I)

    both ends set to lacp passive:

    Group Port-channel Protocol Ports
    ——+————-+———–+———————————————–
    1 Po1(SD) LACP Gi1/0/1(I) Gi1/0/2(I)

    to be honest I’m still confused as B D E options will make links capable of negotiating, not all of them will initiate

    A is wrong lacp-auto there’s no such thing
    C is also wrong pagp-on doesn’t use any protocol to negotiate, pagp is only used locally to make sure ports to be bundled are compatible etc

    ref:
    https://www.cisco.com/c/en/us/td/docs/ios/12_2sb/feature/guide/gigeth.html
    https://www.cisco.com/c/en/us/support/docs/switches/catalyst-4000-series-switches/23408-140.html#lacp_pagp

  12. patta
    May 23rd, 2018

    Q5 is very tricky, they don’t ask which two options will allow to form ether channel but in which modes port channel is capable of negotiation

    some info form cisco,

    Passive—Places a port into a passive negotiating state, in which the port responds to LACP packets it receives but does not initiate LACP negotiation. In this mode, the port channel group attaches the interface to the bundle.

    auto—Places an interface into a passive negotiation state, in which the interface responds to PAgP packets that the interface receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets.

    to be honest I’m still confused as B D E options will make links capable of negotiating, not all of them will initiate

    A is wrong lacp-auto there’s no such thing
    C is also wrong pagp-on doesn’t use any protocol to negotiate, pagp is only used locally to make sure ports to be bundled are compatible etc

  13. kingkong56dasd
    May 30th, 2018

    100% valid CCNP Exam Questions

    dumps
    pro
    dot
    com

  14. Raito
    June 8th, 2018

    Q10:
    The topology that certprepare draws here is not correct…

    “A single server in company is connected VIA ETHERCHANNEL to a single upstream switch.”

    However, in the topology the server is connected with a single link and the etherchannel is between two switches.
    I think destination MAC makes sense as a solution here, since the question asks for the direction from the routers to the server and the server has two MAC addresses.

  1. No trackbacks yet.