DHCP assigned unregistered IP address

[Glenn Dawson]

At 09:49 PM 7/13/2005, Bob Hall wrote:
>Tonight, during a thunderstorm, I shutdown the household FBSD internet
>gateway. After the storm passed, I booted it up again, only to discover
>that during the bootup, my ISP's DHCP server had assigned me a new IP
>address. That wasn't a problem in itself, but the new address was
>192.168.100.11, an unregistered address.
>
>The result was that I could ping my ISP's DHCP server, but I couldn't do
>anything that required a URL. When I talked to a tech at my ISP, she
>couldn't see my modem. She insisted that the IP address wasn't a
>problem because I had a router. (Huh?) After she scheduled a visit from
>a tech for tomorrow and I hung up, I released the lease on the
>unregistered address a few times until the DHCP server gave me a new,
>registered address. Magically, everthing worked again. When I cancel the
>tech visit tomorrow, I'll have them check to see if they can see my
>modem again. Obviously, the unregistered IP address screwed up my system
>and theirs.

Sounds like you have one of the motorola cable modems.  They will assign 
exactly that address if they are turned on and can't communicate with the 
cable companies network.


>My understanding, after extensive reading, is that the unregistered
>address could only have come from my ISP's DHCP server. However, I don't
>know why they would have assigned an IP address that screwed up their
>systems and mine. I'm wondering if dhclient could have assigned this
>address to itself if it encountered a problem during bootup. I don't
>believe this could happen, but I don't understand why my ISP would shoot
>itself (and me) in the foot.
>
>Does anyone know enough about dhclient to say definitely whether it
>could have been the culprit?  Anybody with enough experience with ISPs
>to say why they would have assigned an unregistered IP address that
>broke both systems?

see above.

-Glenn

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