I thought I understood DHCP

[Jophster]

Hi guys
I seem to have a recurring problem in my household network.

I have an ADSL Modem Router (changes depending on my frustration with current model!) but a common problem that seems to occur is that when I try to connect anything such as a MacBook to the network, it gives the computer the most random IP Address imaginable with a subnet mask of 255.255.0.0.

Any ideas as to why this may be happening?

 

[DeltaMac]

Despite your concern about the actual IP address, are you able to connect and browse the internet?

Are you trying to connect through wifi, or ethernet?

If you power-cycle your DSL modem (turn OFF, or unplug the power cord, then on again), then try to connect with your MacBook, what appears as the IP address in the MacBook's Network pref pane?

 

[Jophster]

Unable to connect to the internet - can't even login to the gateway - the gateway IP is also a strange concoction!

Connecting through WiFi.

Rebooting can make it work - buts its just sporadic, it will sometimes just drop completely and then pick up again with this odd set of IP details.

There is another router on the network but its relaying DHCP work to the other one in the house and is only really being used as a WiFi Access Point, don't think that should affect anything?

 

[dimme]

If you have two routers connected to your modem and they are both serving DHCP addresses they need to be using different sets of P numbers

 

[chris.k]

If you get a 169.254 address it generally means your DHCP service isn't working properly. Those are "self assigned addresses" (mask 255.255.0.0 /16) which the computer gives itself after a while if it cannot find the DHCP server.

 

[Consultant]

Hi guys
I seem to have a recurring problem in my household network.

Contact your internet service provider for support.

I am guessing you only have a modem (with 1 ethernet port), not router. Some old modems are set to allow use by only one computer and you need to power cycle it to use with another device. Solution is to get an actual router such as the Apple AirPort Extreme or Express.