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CDP & LLDP Questions 2

September 20th, 2017 in SWITCH 300-115 Go to comments

Question 1

Explanation

Cisco Discovery Protocol Version 2 has three additional type, length, values (TLVs): VTP Management Domain Name, Native VLAN, and full/half-Duplex.

Question 2

Explanation

The default CDP timer (the frequency a router sends CDP packets) is 60 seconds and the hold time (the amount of time a receiving device retains the CDP information sent by other devices) is 180 seconds. In this case the question wants to ask about CDP timer. Therefore half of the default CDP timer is 30 seconds.

Question 3

Question 4

Question 5

Question 7

Explanation

The information contained in Cisco Discovery Protocol advertisements varies based on the type of device and the installed version of the operating system. Some of the information that Cisco Discovery Protocol can learn includes:
+ Cisco IOS version running on Cisco devices
+ Hardware platform of devices
+ IP addresses of interfaces on devices
+ Locally connected devices advertising Cisco Discovery Protocol
+ Interfaces active on Cisco devices, including encapsulation type
+ Hostname
+ Duplex setting
+ VLAN Trunking Protocol (VTP) domain
+ Native VLAN

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html

Question 8

Explanation

You must enable CDP on the switch port connected to the Cisco IP Phone to send the configuration to the phone (which includes the Voice VLAN to be used).

Question 9

Question 10

 

Comments
  1. f
    September 28th, 2017

    q12
    cdp can share VTP information .
    i think E also correct . please advice !

  2. switchy
    October 22nd, 2017

    I think CDP only shows what VTP domain the other device belongs to but not exactly VTP information. I guess VTP has it’s own packets to send out and NOT use CDP packets to tag the information.

  3. MZI John
    November 19th, 2017

    Question 10
    Which two settings are part of a default LLDP configuration? (Choose two)
    A. The LLDP hold time is 60 seconds
    B. The LLDP global state is disabled
    C. The LLDP reinitialisation delay is 5 seconds
    D. The LLDP interface state is enabled
    E. The LLDP timer is 60 seconds
    Answer: B D
    I think the ANSWER D is not correct, Please see the bellow link on Default LLDP Configuration.
    https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/15-2_4_e/configurationguide/b_1524e_consolidated_3750x_3560x_cg/b_1524e_consolidated_3750x_3560x_cg_chapter_010011.html

  4. Jack
    November 26th, 2017

    hi does any one have an idea on CDP concepts,

    Which two statements about CDP are true? (Choose two)
    A. CDP uses a TLV to advertise the native VLAN
    B. CDP is not supported with SNMP
    C. CDP is supported on Frame Relay sub interfaces
    D. CDP runs on OSI layer 2
    E. CDP runs on OSI layer 1

    i am not sure if Answer C is correct or not , i could see in some of the website that answer C is correct.
    in this website we have A and D is correct
    kindly clarify my doubt.

    Thank You,
    Jack

  5. SwitchO
    November 26th, 2017

    @Jack CDP is Not supported on Frame relay.
    Trust me on this one.
    CDP will transit through the Frame Relay PVC carried by the FR switch. By default it’s disabled on FR interfaces, but you can enable it. Then the end point routers will see one another, but you won’t see the intermediate frame switch(es).
    Yes, CDP is layer-2. However, the frame switch is a frame switch. CDP isn’t frame-relay, so it will ignore it. Once a PVC is created, CDP will flow through it, but not before.

  6. Anonymous
    November 28th, 2017

    Default LLDP Configuration
    Feature
    Default Setting
    LLDP global state
    Disabled
    LLDP holdtime (before discarding)
    120 seconds
    LLDP timer (packet update frequency)
    30 seconds
    LLDP reinitialization delay
    2 seconds
    LLDP tlv-select
    Disabled to send and receive all TLVs
    LLDP interface state
    Disabled
    LLDP receive
    Disabled
    LLDP transmit
    Disabled
    LLDP med-tlv-select
    Disabled to send all LLDP-MED TLVs. When LLDP is globally enabled, LLDP-MED-TLV is also enabled

  7. TKasali
    December 2nd, 2017

    Default LLDP Configuration
    Default Setting

    LLDP global state : Disabled

    LLDP holdtime (before discarding): 120 seconds

    LLDP timer (packet update frequency): 30 seconds

    LLDP reinitialization delay: 2 seconds

    LLDP tlv-select: Disabled to send and receive all TLVs

    LLDP interface state: Disabled

    LLDP receive: Disabled

    LLDP transmit: Disabled

    LLDP med-tlv-select: Disabled to send all LLDP-MED TLVs. When LLDP is globally enabled, LLDP-MED-TLV is also enabled.

  8. Marcus
    December 3rd, 2017

    Hello, guys! Could you explain why Q10 answer D is correct and why Q12 answer C is correct? I tested CDP for Q12 with native VLAN mismatch in CPT and UNL. Yes, I get a notification every time, but CDP still works and I can see neighbor switch via ‘show cdp neighbors’.

  9. Addie
    December 3rd, 2017

    Question10 ans D is not correct as Cisco documentation says. So anybody bother to explain why D is correct?

  10. wasntme
    December 13th, 2017

    @Addie, i think that is correct in fact. It is the default after LLDp has been enabled globally.
    have a look at this link for more details.
    https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/system_management/configuration/guide/sm_nx_os_cg/sm_lldp.html#74642

  11. joe
    December 18th, 2017

    can someone explain further onto question 12 as to why C. It is disabled when switches have mismatched native VLANs is correct ?

    I ran a short lab with 2 switches and purposeless configured an incorrect native vlan and I was seeing native vlan mismatches via cdp and was also able to still run show cdp neighbor. I am thinking the correct answers are B,E cand anyone advise ?

  12. BreakFix
    December 30th, 2017

    100% in agreement with Joe – E is correct, not C.
    !
    Mismatched native VLANs never have and never will bring CDP down on a port.
    In fact, CDP is what discovered the native VLAN mismatch in the first place.
    !
    Parse “sh log” to the CLI and you will see the error endlessly being logged by CDP because CDP is alive and well on the port in question.
    !
    Come to think of, I’ve never heard of a protocol engineered to detect a condition who’s actions upon detecting said condition would be to disable thy self.
    !
    Not saying such a protocol doesn’t or couldn’t exist, It’s just that the concept of a suicidal protocol makes no sense to me.
    !
    Anyway. . . E is correct, not C.
    VTP relies on Cisco Discovery Protocol to carry VTP domain information.
    !
    TVL fields are blocks of information embedded in CDP advertisements.
    “VTP Management Domain” is a TLV field that exists within CDP advertisements.
    !
    The “VTP Management Domain” TLV field advertises exactly what it’s name implies.
    It advertises the configured VTP management domain name of the system.
    !
    Please update Question 12 to reflect B & E to be correct.
    !
    Hope you found this both entertaining and informative.

  13. Anonymous
    January 11th, 2018

    Fellas,
    Question 10 is not correctly formed, it ask for 2 answers, but only 1 is correct, which is B.
    Where did this question come from? Cisco exams?

  14. Anonymous
    January 11th, 2018

    Question 12.
    There is only 1 correct answer, B.
    C is incorrect, as CDP is used only for Syslog Lv4 info, informing this “%CDP-4-NATIVE_VLAN_MISMATCH”.
    CDP is running even when that syslog info is showing.
    Question 12 is not consistent with real world environment, please review it, as it is misleading people.

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    April 18th, 2018

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  16. madestro
    May 21st, 2018

    So I believe it was question 12 that has been already removed from here. It is still in the Quiz section so it should be put back up here. I can only see 10 questions. Anyhow, this is the question:

    Which 2 statements about CDP are true? (Choose two)
    A Devices with CDP send advertisements to broadcast address periodically
    B It can be disabled only at interface level
    C It is disabled when switches have native VLAN mismatch
    D VTP relies on CDP to carry VTP domain information
    E Devices with CDP send advertisements to multicast address periodically

    So, we know right off the bat that A is not correct and thus E is correct. We also know that B is not correct as we can use (config)#no cdp run to disable CDP. So this leaves us with C and D.
    D is incorrect as you can disable CDP entirely and still run VTP in your switch domain. VTP information will have its own advertisements. Notice it says “relies” as in “this is the only way to get VTP info to the other switch” and that is false.
    That would leave C as the other answer, but is it correct though? Well lets look at the answer
    “It is disabled when switches have native VLAN mismatch”
    Nowhere does it say that this should be the default behavior (and it isn’t) but we know that CDP will send syslog messages often advising the Native VLAN mismatch. So the recommendation when that happens is to disable CDP for that interface (if the intended design was to have different Native VLANs on that trunk link of course) and that makes C a correct answer.

    Cisco exams are incredibly tricky like that. Answers are usually the “best one” and not always fully correct. Is true that CDP is not disabled BY DEFAULT when there is a Native VLAN mismatch but nowhere in option C does it say that is disabled by default.

  17. q10
    July 26th, 2018
  18. chuba
    August 1st, 2018

    q10. the questions says chose two answer from Five Choice .right answer is will be
    A. LLDP hold time 60 —-wrong it is 120 sec
    B. LLDP global state disabled by default—–Right
    C. LLDP reintialization delay time 5 seconds—–Wrong it is 2 sec
    D. LLDP default interface state is enabled —— Right (if even cisco documentation shows as Disabled)
    E. LLDP Timer is 60 seconds—-wrong it is 30 seconds.

    What do you think.

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    August 16th, 2018

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