dhclient oddness?

[Lowell Gilbert]

Mark Cullen <mark.cullen at dsl.pipex.com> writes:

> Lowell Gilbert wrote:
> > Mark Cullen <mark.cullen at dsl.pipex.com> writes:
> >
> >>Right, I have this weird annoying issue with my modem which I have
> >>finally got around to looking in to. Basically, it's all good and
> >>works fine (obviously, otherwise I wouldn't be here!), except when I
> >>reboot the internet computer the IP will change, the connection
> >>DOESN'T drop, but the IP does change. I have just now narrowed this
> >>down to some sort of problem with dhcp I think.
> >>
> >>The modem has a dhcpd server built in, which sends out the internet IP
> >>address to the computers network card. It seems, whenever the dhcp
> >>client, dhclient in this case, gets restarted it'll get the old ip
> >>address (the first chunk of the quote below, before the <freeze>),
> >>natd will update itself, but then the connection will just stall until
> >>dhclient does the next DHCPREQUEST thing (47 seconds in this case?)
> >>.. then the modem sends back a DHCPNAK and I get a different IP
> >>address. Any ideas why this might be happening?
> > Your "modem" is clearly the source of the problem, and it seems
> > unlikely that anything on the FreeBSD side could help, aside from
> > maybe forcing a lease free before starting dhclient on startup.
> > I'd try looking at the configuration for that "modem" device, or
> > possibly for a firmware upgrade for it.
> >
> 
> Could you explain what's going on to me? I mean, in simplified terms,
> what exactly is causing the modem to get a new IP address when
> dhclient restarts?  I have contacted them about the issue and they
> seem to think it's an O/S problem (well, it's *obviously* not an issue
> with their modem now, is it? :-P).

Okay, now I'm confused.  I thought your FreeBSD machine was the one
being issued a new address, not the modem.  [And that since the
address was being issued *by* the modem, it was making the decision
about which address to choose.  I guess that means I was assuming your
"modem" was doing NAT.  Does the modem have an address at all?

> How would I go about forcing a 'lease free'? Delete dhclient.leases,
> or some option somewhere that I missed?

I'm pretty sure that dhclient(8) has an command-line option to do it.

> As for configuration, there's no config for the DHCP server and
> there's never been a firmware upgrade for it (this is the only issue I
> have EVER had with it and I expect most users don't notice it).

Since you've rebooted your computer anyway, why do you care?  You've
just lost all of your connections already.