Home > Ticket 13 – DHCP Helper-address

Ticket 13 – DHCP Helper-address

March 18th, 2015 in TSHOOT v2 Go to comments

Configuration on DSW1:

!
interface Vlan 10
 ip address 10.2.1.1 255.255.255.0
 ip helper-address 10.2.21.129
!

Note: In this ticket you will find port-security configured on ASW1 but it is not the problem as the port-security is good (check with the “show interface fa1/0/1” command on ASW1. Also you can easily identify this ticket with the “ipconfig” command on Client1, which shows APIPA address (169.254.x.x).

Ans1) DSW1
Ans2) IP DHCP Server (or DHCP)
Ans3) on DSW1 delete “ip helper-address 10.2.21.129” and apply “ip helper-address 10.1.21.129” command

Comments (17) Comments
Comment pages
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  1. Anonymous
    November 18th, 2017

    Can anyone explain why helper address is 10.1.21.129 ?

  2. Anonymous
    November 19th, 2017

    this question is still valid as of today

  3. gs
    November 21st, 2017

    10.1.21.129 is the Lo1 address on R4.

  4. failed-test
    November 23rd, 2017

    This question is valid. However the Clients are assigned an IP (which in real life they shouln’t) which may cause this question to throw you off balance.

  5. GATA
    December 1st, 2017

    I didn’t get this one

  6. G-unit
    December 11th, 2017

    The clients actually get an APIPA address 169.254.x.x.

  7. Just_passed
    December 13th, 2017

    Confirmed, clients get 169.254.x.x addresses now

  8. Gav
    December 27th, 2017

    **@NetworkTUT or anyone who could answer –**

    Could someone please advise how we get to know from config that DHCP is with IP 10.1.21.129?
    I have my exam day after tomorrow so would appreciate prompt response

  9. Gav
    December 28th, 2017

    Guys – could anyone please respond to my question above – its urgent

    Question is:
    Could someone please advise how we get to know from config that DHCP is with IP 10.1.21.129?

    In exam – IPs etc would change and there is no mention anywhere that loopback on R4 is the DHCP server IP. So my question is – how would we know in exam what interface is going to be used as DHCP server

    Kindly assist
    Gav

  10. NotYou
    December 28th, 2017

    @Gav. The topology has an arrow pointing out R4 is DHCP. R4 has DHCP configuration. In show run, it shows a description on Lo1 that it is Helper Loopback

  11. Fattah RazzaqghanimughnI
    January 4th, 2018

    Silly…. I spent unnecessary time to troubleshoot the Sim Labs from networktut.com which is not even mentioned in the question. This sim have soooo many problems which are not stated in this page:

    1) EIGRP continues to sending routing updates from DSW1 and DSW2 on VLAN20 via ASW2, therefore, under “router eigrp 10” we need to enter command “passive-interface Vlan20” both in DSW1 and DSW2.

    2) Client1 and Client2 will never get DHCP IP ever, ever, never, because in R4 thereare exclusion command line “ip dhcp excluded-address 10.2.1.1 10.2.1.253”, we need to delete this line by entering command in global configuration mode “no ip dhcp excluded-address 10.2.1.1 10.2.1.253”, and change it with another command line “ip dhcp excluded-address 10.2.1.1 10.2.1.2″

    3) There are line ” mac-address 00e0.a3e3.3901″ under “interface Vlan10” on DSW1, I don’t know what is this effect to, but I can not remove this line.

    At last, I set static IP in Client1 and now it can ping the webserver 209.65.200.241.

    I’ve paid for premium membership, and well, in the premium the tickets are in different order.

  12. Fattah RazzaqghanimughnI
    January 4th, 2018

    Silly…. I spent unnecessary time to troubleshoot the Sim Labs from networktut.com which is not even mentioned in the question. This sim have soooo many problems which are not stated in this page:

    1) EIGRP continues to sending routing updates from DSW1 and DSW2 on VLAN20 via ASW2, therefore, under “router eigrp 10” we need to enter command “passive-interface Vlan20” both in DSW1 and DSW2.

    2) Client1 and Client2 will never get DHCP IP ever, ever, never, because in R4 thereare exclusion command line “ip dhcp excluded-address 10.2.1.1 10.2.1.253”, we need to delete this line by entering command in global configuration mode “no ip dhcp excluded-address 10.2.1.1 10.2.1.253”, and change it with another command line “ip dhcp excluded-address 10.2.1.1 10.2.1.2″

    3) There is no DHCP IP Pool configured yet. We have to create it our own. From global configuration mode enter “ip dhcp pool VLAN_10_CLIENTS”, enter “network 10.2.1.0 255.255.255.0”, enter “default-router 10.2.1.254”

    And there you go, Client1 and Client2 can acquired DHCP IP and now they can ping the webserver 209.65.200.241.

    I’ve paid for premium membership, and well, in the premium the tickets are in different order.

  13. Integrals
    January 8th, 2018

    @ Gav
    @ NotYou

    The Questions clearly says, “The client workstations receive their IP address and default gateway via R4’s DHCP server”

    So, it is safe to assume that R4 is the DHCP Server.

    But as NotYou says, when I do a show run in R4, it is not showing the description ‘Helper’ anywhere. Not under the Loopback 1 interface, and not under the DHCP configuration either

    So, I am not sure how to identify which interface is gonna act as the DHCP Server in case if it is a different IP Address.

    @ Networktut, any suggestions?

  14. Mangal76
    January 10th, 2018

    If you go back few pages some one has actually answered this however here is my understanding of it.

    if you look at the top of this page where the answer is shown, it does tell you that DSW1 is where the helper is located. When you do “Show run” helper ip will show up under “Interface Vlan 10”. In the real exam, look at the topology and it will eventually tell you where the clients are getting their IP addresses from. This should be in the scenario section if not just type the command ipconfig on one of the clients to see which is the DHCP server.

    Once you locate the DHCP server (R4 in network tut ticket) than do “show run” or “show ip interface Loopback1” to find out the ip address and cross check if the Helper address IP on DSW1 and Loopback1 ip address is identical. if not you found the issue.

    I hope this helps.

  15. Abdul Ghafoor
    January 11th, 2018

    For GAV and GATA
    I hope you understand this ticket by now, Mangal76 explained it very well.
    Just in case, let me explain this again from a different angle.

    If you look at IPv4 Layer 3 Topology, you will notice that DHCP Server is on the R4. Hence the address of DHCP Server must be loopback address of R4. You must call it on the Distribution Switch/Router (DSW1) as a ip-helper address so it knows where to pull ip addresses for the devices, i.e. PC (Client 1).

    I hope this helps.

  16. Albert
    January 16th, 2018

    I used Testcollection 300-135 test questions. His 300-135 practice exam really valid and correct answer. Guys, you can also pass the 300-135 exam after using Testcollection 300-135 practice test. https://testcollection.us/300-135-vce-download.html

  17. Anonymous
    January 17th, 2018

    packet capture started working for me after i updated the helper address 10.1.4.5

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