How to find my ISP's DHCP server address?

Discussion in 'privacy technology' started by Thelps, Apr 20, 2018.

  1. Thelps

    Thelps Registered Member

    Joined:
    Apr 1, 2012
    Posts:
    46
    How can I determine my ISP's DHCP server address?

    Interested in specifying that address to my Router so that, when obtaining a new IP-lease, I can find a way to avoid the whole broadcasting on all channels, hurling my router's MAC Address around.

    If I know the ISP's DHCP server address I can avoid parts of the initial DHCP-lease obtaining process.
     
  2. Stefan Froberg

    Stefan Froberg Registered Member

    Joined:
    Jul 30, 2014
    Posts:
    747
    It's usually the same as gateway address.
    On windows you can do ipconfig or ipconfig /all to make sure of the DHCP server address.
    Example, here's the stuff from my virtualbox windows installation:
    upload_2018-4-20_17-11-58.png

    EDIT: and of course, if you want to put that address to your router then you would
    need to take it out temporarily, directly connect you comp to your ISP, wait for
    dhcp lease and then do the above command to get the DHCP server of your ISP.

    Also, I think most Routers will have page or option from their WebUI that show
    DHCP server address of upstream?

    EDIT2: To tell the truth, I did not even know that it's possible to have DHCP unicast from client side but apparently it is possible:
    http://www.freesoft.org/CIE/RFC/2131/33.htm
    Heh, old dog learns new tricks...
     
    Last edited: Apr 20, 2018
  3. TairikuOkami

    TairikuOkami Registered Member

    Joined:
    Oct 10, 2005
    Posts:
    3,417
    Location:
    Slovakia
    You can also use tracert command or a software like that. 10.10.10.10 is my router and 10.10.24.1 is the first ISP's DHCP server.
     

    Attached Files:

  4. reasonablePrivacy

    reasonablePrivacy Registered Member

    Joined:
    Oct 7, 2017
    Posts:
    1,999
    Location:
    Member state of European Union
    Probably this DHCP server address can be read from router. It depends on vendor, model of that router how to obtain that.

    I don't know whether you have router and modem (two separate devices) or device with both these things integrated.

    If you have separate modem, connect PC directly to modem.
    I remember that you had nmap installed. Use these commands in cmd.exe:
    Code:
    cd "C:\Program Files (x86)\Nmap"
    nmap.exe --script="broadcast-dhcp-discover"
    Be aware the it spoofs MAC address and in some cases (very rare) network can be configured to ignore or respond some garbage to unknown MAC addresses.
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.