From owner-freebsd-questions@freebsd.org Fri Feb 28 06:45:34 2020 Return-Path: Delivered-To: freebsd-questions@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 3F62E25B925 for ; Fri, 28 Feb 2020 06:45:34 +0000 (UTC) (envelope-from SRS0=n/vY=4Q=mail.sermon-archive.info=doug@sermon-archive.info) Received: from mail.sermon-archive.info (sermon-archive.info [71.177.216.148]) by mx1.freebsd.org (Postfix) with ESMTP id 48TKmX44r6z3NlH for ; Fri, 28 Feb 2020 06:45:32 +0000 (UTC) (envelope-from SRS0=n/vY=4Q=mail.sermon-archive.info=doug@sermon-archive.info) Received: from [10.0.1.251] (mini [10.0.1.251]) by mail.sermon-archive.info (Postfix) with ESMTPSA id 48TKmV4jZBz2fjRb; Thu, 27 Feb 2020 22:45:30 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Subject: Re: DNS resolution From: Doug Hardie In-Reply-To: <028a9ca5-b935-3de1-5edd-adb959c1116a@heuristicsystems.com.au> Date: Thu, 27 Feb 2020 22:45:30 -0800 Cc: freebsd-questions@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: <16E91023-D8C4-4A40-9EBA-183443D610B2@mail.sermon-archive.info> References: <93893C00-93BD-4C71-943E-8751DF2854FE@mail.sermon-archive.info> <028a9ca5-b935-3de1-5edd-adb959c1116a@heuristicsystems.com.au> To: Dewayne Geraghty X-Mailer: Apple Mail (2.3445.104.11) X-Virus-Scanned: clamav-milter 0.101.4 at mail X-Virus-Status: Clean X-Rspamd-Queue-Id: 48TKmX44r6z3NlH X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; dkim=none; spf=pass (mx1.freebsd.org: domain of SRS0=n/vY=4Q=mail.sermon-archive.info=doug@sermon-archive.info designates 71.177.216.148 as permitted sender) smtp.mailfrom=SRS0=n/vY=4Q=mail.sermon-archive.info=doug@sermon-archive.info X-Spamd-Result: default: False [-1.09 / 15.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; NEURAL_HAM_MEDIUM(-0.74)[-0.737,0]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+ip4:71.177.216.148]; MV_CASE(0.50)[]; MIME_GOOD(-0.10)[text/plain]; IP_SCORE(0.03)[asn: 5650(0.20), country: US(-0.05)]; NEURAL_HAM_LONG(-0.98)[-0.979,0]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; RCVD_IN_DNSWL_NONE(0.00)[148.216.177.71.list.dnswl.org : 127.0.10.0]; FORGED_SENDER(0.30)[bc979@lafn.org,SRS0=n/vY=4Q=mail.sermon-archive.info=doug@sermon-archive.info]; RCVD_NO_TLS_LAST(0.10)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:5650, ipnet:71.177.216.0/23, country:US]; FROM_NEQ_ENVFROM(0.00)[bc979@lafn.org,SRS0=n/vY=4Q=mail.sermon-archive.info=doug@sermon-archive.info]; RCVD_COUNT_TWO(0.00)[2] X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 28 Feb 2020 06:45:34 -0000 > On 27 February 2020, at 22:22, Dewayne Geraghty = wrote: >=20 > On 28/02/2020 11:34 am, Doug Hardie wrote: >> I have encountered an inconsistent result in DNS resolution that I am = unable to explain. The situation is three servers with completely = different IP addresses on three different internet connections. All = three are via different companies. In the DNS records for the domain I = have an A record for each server with the name A.domain, B.domain, and = C.domain. Each points to the appropriate IP address. The name = www.domain (and also just domain) have 3 A records: one for each of the = 3 servers. The goal is to have a fail over such that A is the primary = server, and if it fails, then try B, and finally C. Load balancing is = not desirable because the web transactions require numerous exchanges = and need to all use the same server. >>=20 >> On Frontier, Spectrum, and Charter connections, host www.domain lists = the 3 servers in the order they are defined in the DNS records. Every = time I run host I get the same result. However, there is one PC running = windows 10 that connects via the charter supplied modem and is = configured for DNS at the modem address that gets the addresses in = random order. It appears to be trying to do load balancing. When I use = Charter's official DNS servers, I don't see that. But if I use the = modem then even FreeBSD 11.1 gets the random results. >>=20 >> The spectrum interface has the same issue. The official DNS servers = are consistent, the modem as a DNS server is random. I thought the TTL = for the domain would be honored by the DNS servers. That doesn't always = appear to be the case, or the modem DNS servers are rotating their = responses from their cache. However, shouldn't the client computers = cache the DNS response? Windows does not appear to be doing that. >>=20 >>=20 > Yes, Windows boxes cache the results, to check, open cmd prompt > ipconfig /displaydns >=20 > I'd suggest that the modem isn't caching and rotating dns responses as > expected. I can't see what DNS servers the modem is using, but I suspect they are = the "official" ones per the ISP. When I use those directly, there is no = rotating. When I go to the modem with either windows or FreeBSD then I = get rotation. I don't see where else the rotation could be occurring. =20= -- Doug