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Date:      Tue, 15 Mar 2016 18:06:12 -0500 (CDT)
From:      "Valeri Galtsev" <galtsev@kicp.uchicago.edu>
To:        "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org>
Cc:        "Guy Harrison" <gfh@swampdog.co.uk>, "freebsd-questions\@freebsd.org" <freebsd-questions@freebsd.org>
Subject:   Re: dhcpd, iscsi and a raspberry pi
Message-ID:  <26023.128.135.52.6.1458083172.squirrel@cosmo.uchicago.edu>
In-Reply-To: <4437rrjreh.fsf@lowell-desk.lan>
References:  <201603151632.14124.gfh@swampdog.co.uk> <56E84CA8.4080603@qeng-ho.org> <4D586A3A-9972-427D-B32D-90806B0C0AB7@thehowies.com> <201603152131.23144.gfh@swampdog.co.uk> <44egbbiewf.fsf@be-well.ilk.org> <4437rrjreh.fsf@lowell-desk.lan>

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On Tue, March 15, 2016 5:41 pm, Lowell Gilbert wrote:
> Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> writes:
>
>> I thought dhcpd would use MAC address

Correct: DHCP server uses MAC address to identify clients. DHCP server can
be configured to give some client (identified by MAC address) the same IP
(thus making that client appear with static IP. Windoze world calls this
"DHCP reservation")

>> if the client didn't provide
>> anything else. I'll check if I get a chance.
>
> Confirmed. My dual-boot machine has no special settings in the server's
> dhcp.conf, and gets the same address regardless of which OS it's using.
> It even offers a different hostname on each OS.

If DHCP lease didn't expire, DHCP server will give client the same IP (the
one that is in still valid DHCP lease for this client). This is what most
likely you observe. If DHCP client never goes away from network, chance is
it never will change IP (unless DHCP server is specifically configured to
not give client the same IP when lease is renewed. I forgot details how it
is done, I never do it on my DHCP servers).

Hostname: if you are using "hostname" command it reports system hostname
which is configured internally in system configuration files (which
particular files depends on the system). This name will be reported no
matter which IP the machine gets <rant> - except special cases, like on
macintosh where machine changes it's hostname (known to the machine
internally) depending on network connection. This is rare thing (and
drives same person crazy, programmers who write license daemons often can
not "outsmart" macintosh here). </rant>

I hope this clarifies some things.

Valeri

++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++



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