Binding dhclient to a particular network interface

[Jasvinder S. Bahra]

Chuck,

Oddly enough, after the system has finished starting up, running "dhclient
ed1" on the command line does work (though "sockstat -l4" still shows local
address as "*:68").  I could I have sworn that when I tried doing this the
first time I added the dhclient_flags line, it failed.

One thing I noticed as the system was starting up (after adding the
dhclient_flags entry into /etc/rc.conf), was that dhclient completed too
quickly.  Normally when dhclient runs, it usually takes several seconds to
do its thing (i.e... a noticeable delay between the "Starting dhclient"
message appearing and the message immediately after it), however there was
no delay between the appearance of the two messages - dhclient fails
instantly.

I doubt its relevant, but keep in mind this is a very old machine - an Intel
Pentium 120MHz, 48MB RAM equipped with two ISA network cards, running
FreeBSD 5.5.

I'm afraid I cant run the command you suggested on the DHCP server, as the
DHCP server in this case is built into the cable modem (to which I do not
have shell access, if it even provides such).  As for sticking a switch in
between and connecting an a third PC to monitor - i'd prefer to leave that
as a last resort for the time being as finding and setting up the additional
hardware will be a bit of a pain.

If you (or indeed anyone else) has any other suggestions, please do share.

Thanks,

Jazz

----- Original Message ----- 
From: "Chuck Swiger" <cswiger at mac.com>
To: "Jasvinder S. Bahra" <bbdl21548 at blueyonder.co.uk>
Cc: "FreeBSD-questions List" <freebsd-questions at freebsd.org>
Sent: Monday, July 30, 2007 9:38 PM
Subject: Re: Binding dhclient to a particular network interface


> Jasvinder S. Bahra wrote:
> > Chuck,
> >
> > I gave this a shot, but this stopped the interface being assigned an IP
> > address at all (i.e... before the change, the interface had a valid IP
> > address assigned by the DHCP server in my cable modem, but after making
the
> > change and restarting, the "ifconfig" command shows the interface having
an
> > IP address of 0.0.0.0).
> >
> > I do agree though - the man page explicitly says that this should work.
>
> Does running "dhclient ed1" from the command line work?
> Is the DHCP server providing the right answer?
>
> Running "tcpdump -s 0 arp or port bootps" would give you insight into what
the
> network is seeing, at least.  Doing this from your DHCP server or a laptop
on
> a hub with the interface in question would be useful vantages, or a
"trunk" or
> "span" port on a smart switch, depending on what you might have handy.
>
> -- 
> -Chuck