dhclient: lease renewal woes

Mr Dash Four mr.dash.four at googlemail.com
Wed Aug 29 14:25:45 UTC 2012

Hi Glenn,

> Do other dhcp clients (eg windows) work ok with the dhcp server in the
> cable modem? Can you look at the settings those clients get from the cable
> modem? eg on windows "ipconfig /all"
Nope. The cable modem sits directly between the outside world and my 
firewall, which shields/protects my entire set of private networks (all 
Linux based, with the odd exception of Windows 7 and Windows XP). In 
essence, this is my exit point where all external traffic is redirected.

> I would have thought setting the server-identifier to the private
> ip-address of the cable modem would be the right thing.
Me too, but it doesn't seem to work. I would have thought that since I 
have no direct control over dhcp-server-identifier (so the man page 
says) the "supersede" statement in my dhclient.conf file was the right 
way to go. It didn't work though and from what I remember the cable 
modem responded with a broadcast ( in one of its replies 
and that got ignored by dhlcient since this dhcp-server-identifier was 
set to a single value (yeah, chicken and egg scenario right there). If I 
can't find any viable solution I will repeat that experiment and post 
the results here.

>  Is there anything you can configure on the cable modem?
Nope, I'll be breaking my customer agreement with the provider if I 
touch anything there. I am not even supposed to look at its logs or 
anything else on the admin side of this device.

> Otherwise do you have a system that you could run your own dhcp server on?
That won't help me much because, as I stated above, this is my exit 
point to the "world" and without this I won't be connected at all.

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