From owner-freebsd-questions@FreeBSD.ORG Sat Oct 28 14:09:24 2006 Return-Path: X-Original-To: questions@freebsd.org Delivered-To: freebsd-questions@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B461916A513 for ; Sat, 28 Oct 2006 14:09:23 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (ns0.infracaninophile.co.uk [81.187.76.162]) by mx1.FreeBSD.org (Postfix) with ESMTP id A9BB443DAC for ; Sat, 28 Oct 2006 14:08:50 +0000 (GMT) (envelope-from m.seaman@infracaninophile.co.uk) Received: from [IPv6:::1] (localhost [IPv6:::1]) by smtp.infracaninophile.co.uk (8.13.8/8.13.8) with ESMTP id k9SE8GNn034920; Sat, 28 Oct 2006 15:08:16 +0100 (BST) (envelope-from m.seaman@infracaninophile.co.uk) Authentication-Results: smtp.infracaninophile.co.uk from=m.seaman@infracaninophile.co.uk; sender-id=softfail; spf=softfail X-SenderID: Sendmail Sender-ID Filter v0.2.14 smtp.infracaninophile.co.uk k9SE8GNn034920 Message-ID: <45436449.4020509@infracaninophile.co.uk> Date: Sat, 28 Oct 2006 15:08:09 +0100 From: Matthew Seaman Organization: Infracaninophile User-Agent: Thunderbird 1.5.0.7 (X11/20061015) MIME-Version: 1.0 To: Robert Huff References: <20061028025626.GA39172@skytracker.ca> <2B8A4ACE-ACE3-44D0-B40B-26D96D43A4E8@shire.net> <17731.22324.706536.159980@jerusalem.litteratus.org> In-Reply-To: <17731.22324.706536.159980@jerusalem.litteratus.org> X-Enigmail-Version: 0.94.0.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigD99245F0B01B2CC172911DFF" X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0.2 (smtp.infracaninophile.co.uk [IPv6:::1]); Sat, 28 Oct 2006 15:08:36 +0100 (BST) X-Virus-Scanned: ClamAV 0.88.5/2127/Sat Oct 28 08:34:04 2006 on happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00, DKIM_POLICY_TESTING, NO_RELAYS autolearn=ham version=3.1.6 X-Spam-Checker-Version: SpamAssassin 3.1.6 (2006-10-03) on happy-idiot-talk.infracaninophile.co.uk Cc: FreeBSD Questions Subject: Re: how to know what DNS server is being used X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 28 Oct 2006 14:09:24 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD99245F0B01B2CC172911DFF Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Robert Huff wrote: > Chad Leigh -- Shire.Net LLC writes: >=20 >> > On my registrars site I have two DNS servers listing. How would >> > I know that 1) both are working. 2) which one is being used. >> =20 >> For #2, do you mean by the world at large? Which one is being >> used when people look up your domain and hosts in your domain? >> Both of them should get used. I don't know what algorithm is >> used but both will be used by people. >=20 > As I understand it, when presented with a list of N>1 possible > nameservers standard resolver libraries will pick one at random and > continue to use it until something changes (nameserver goes > off-line, local cache is flushed, etc.). On recent FreeBSD, the resolver actually iterates through the listed nameserver lines in order, sending the query out to each in turn until it gets a response. It used to be that the resolver would wait for the full 30s DNS timeout before trying the next server (hence the cry dreaded= by sysadmins everywhere that "the Internet is slow today"), but nowadays if the resolver hasn't got an immediate answer it will initiate the secon= d and subsequent queries after a wait of some number of milliseconds and then wait for a response from all of the queried servers. Means that if your first listed DNS server is down, users don't notice the delay before= the second server is queried. Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW --------------enigD99245F0B01B2CC172911DFF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFFQ2RP8Mjk52CukIwRCIzqAJ4o5Zg2w12gmEZCLSSKAdeUkwfGzgCfWgjG Ax4Jy1aRTmVFmW3NgHLOYIE= =nPwu -----END PGP SIGNATURE----- --------------enigD99245F0B01B2CC172911DFF--