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List:       centos
Subject:    [CentOS]  how to increase DNS reliability?
From:       Leroy Tennison <leroy () datavoiceint ! com>
Date:       2019-07-25 13:28:39
Message-ID: YTXPR0101MB1246AEA1C99D86243534B8BACDC10 () YTXPR0101MB1246 ! CANPRD01 ! PROD ! OUTLOOK ! COM
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If you don't want multiple DNS server entries on the client then a master and \
(possibly multiple) slave server configuration can be set up (I'm assuming ISC DNS - \
their solution to redundancy/failover is master and slave servers, this may be the \
way it is with all DNS).  keepalived can be used for fail over and will present a \
single IP address (which the clients would use) shared among the servers.  haproxy or \
alternatives might be another fail over option.  Each technology has its own learning \
curve (and doing this will require at least two) and caveats.  In particular systemd \
doesn't appear to play well with technologies creating IP addresses it doesn't \
manage.  The version of keepalived we're using also has its own nasty quirk as well \
where it comes up assuming it is master until discovered otherwise, this is true even \
if it is configured as backup.  In most cases this is probably either a non-issue (no \
scripts being used) or a minor annoyance.  But if you're using scripts trigger  ed by \
keepalived which make significant (and possibly conflicting) changes to the \
environment then you'll need to embed "intelligence" in them to wait until final \
state is reached or test state before acting or some other option.

________________________________
From: CentOS <centos-bounces@centos.org> on behalf of hw <hw@gc-24.de>
Sent: Thursday, July 25, 2019 7:51:39 AM
To: centos@centos.org <centos@centos.org>
Subject: [EXTERNAL] [CentOS] how to increase DNS reliability?


Hi,

how can DNS reliability, as experienced by clients on the LAN who are
sending queries, be increased?

Would I have to set up some sort of cluster consisting of several
servers all providing DNS services which is reachable under a single
IP address known to the clients?

Just setting up several name servers and making them known to the clients
for the clients to automatically switch isn't a good solution because
the clients take their timeouts and users lacking even the most basic
knowledge inevitably panic when the first name server does not answer
queries.
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E: leroy@datavoiceint.com


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