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.
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: 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...
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.
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.