Date: Thu, 27 Feb 2020 16:34:17 -0800 From: Doug Hardie <bc979@lafn.org> To: FreeBSD <freebsd-questions@freebsd.org> Subject: DNS resolution Message-ID: <93893C00-93BD-4C71-943E-8751DF2854FE@mail.sermon-archive.info>
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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. 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. 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. -- Doug
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