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DHCP Questions 2

October 27th, 2018 Go to comments

Question 1

Explanation

The command “show ip dhcp conflict” displays address conflicts found when addresses are offered to the client. Below is an example:

show_ip_dhcp_conflict.jpg

Question 2

Question 3

Question 4

Question 5

Explanation

In the DHCP pool we need to configure a default gateway (via the “default-route …” command) for the DHCP clients to communicate with outside subnets.

Question 6

Question 7

Explanation

In this case the printer is statically assigned an IP address so we have to make sure DHCP server does not assign the same IP address to another device. We can configure the DHCP server with the command “ip dhcp excluded-address <ip-address>” (suppose it is a Cisco device).

 

Comments (5) Comments
  1. sachu
    December 16th, 2017

    Which command can you enter to display duplicate IP addresses that the DHCP server assigns?
    A. show ip dhcp conflict 10.0.2.12
    B. show ip dhcp database 10.0.2.12
    C. show ip dhcp server statistics
    D. show ip dhcp binding 10.0.2.12

    Can some tell me why the answer A is correct .
    I think answer D is correct because in the new iOS Version 15.2(4)S5, there is no option to enter the IP address after the command sh ip dhcp conflict (***).

  2. raptor
    January 31st, 2018

    @sachu good observation. none of these commands allow to enter specific ip address

    @9tut could you please specify why it is correct?

    thanks

  3. dedesmilion
    March 20th, 2018

    I don’t understand the answer of the question
    – Where does the configuration reside when a helper address is configured to support DHCP?
    Is

    B. on the router closest to the client.

    Can anyone elucidate this question ?

  4. cthelite
    April 2nd, 2018

    Q6:
    None of these answers are actually correct. 9tut chose the closest. Obviously A, B, and D are not correct as we’re referring to DHCP. In regards to answer C:

    “sh ip dhcp binding” shows the DHCP table with all IPs, MACs, Lease Expirations for all pools (NOT trusted/untrusted ports).
    “sh ip dhcp database” shows info about the binding file itself, not what’s in it (file location, when written, last updated).
    “sh ip dhcp snooping” shows info about trusted/untrusted ports.
    “sh ip dhcp snooping database” shows info about the snooping file itself.

    Just the Binding Database refers to the DHCP table. Without snooping enabled there is no concept of Trusted/Untrusted. The Binding DBase and the Snooping DBase are two seperate DBases and two seperate files. I hope the CCNA differentiates them. Maybe answer C originally included the keyword “snooping” in it. After snooping is enabled, the snooping dbase or snooping binding dbase would be the only place that would reference snooping info.

  5. cthelite
    April 2nd, 2018

    @dedesmilion You can google this and quickly get a number of explanations. The act of investigation is paramount to preparing for anything, including the CCNA. Start with the tutorial that 9tut includes with every section (top of most pages). http://congressreiki.ranm.org/?all=dhcp-tutorial

    One thing to note, the first DHCP request from the client is a layer 2 + layer 3 broadcast (destination IP address of 255.255.255.255 and destination MAC address of FF-FF-FF-FF-FF-FF). But remember a router is the boundary of a broadcast domain, so it will drop the packet. Hence the need for a unicast helper address. Good hunting.

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