Re: Understanding DNS, Create an "Failover"
lee wrote:
basti <black.fledermaus@arcor.de> writes:
Hello,
last weekend my primary DNS-Server goes down, and some of my server
can't find each other.
[...]
How can I fix this?
Set up a second name server which operates as slave of your primary one
and use the slave as fallback?
bind, and dns in general, are designed for this:
1. you designate multiple nameservers with your registrar - which in
turns forwards those records to the root nameservers (generally, you're
expected to designate at least a primary and secondary) - so, right off
the bat, when all of your nameservers are "published" (NS records are
returned)
2. the trick is keeping the data synchronized - typically, you'll
maintain the records in one of your nameservers and then enable
synchronization between that server and your secondary server(s) -- bind
supports both push and pull
3. a common practice is to have a "hidden" nameserver, where you
maintain your records (e.g., on your own server), and then push/pull the
definitive data to several other servers (e.g., heavy duty machines
maintained by your data center operator or a commercial service) - that
way you can manage the records on a system you control, but not have to
eat the data load (and potential DOS attacks) of queries from the
outside world
It's a bit tricky to set up the first time, then it just runs itself,
except when you change records. (If I'm a little foggy on the details,
it's because I haven't had to touch our nameservers in a long time.
They just hum along). I would recommend getting a good book on the
subject - "DNS & Bind" from O'Reilly is pretty good, though I don't know
when they've last updated it.
Several other notes:
- While BIND is the definitive nameserver, there are others (e.g.,
PowerDNS). Some of the others might be easier to administer (GUI vs.
text files, that sort of thing).
- Webmin has a nice admin interface for bind.
- dnsstuff.com has some nice tools for monitoring and troubleshooting
DNS, and their free toolset is enough for most things
Or.. you could just farm it all out to someone else. Pretty much every
registrar will provide DNS for you, as well as as lots of other services.
Miles Fidelman
--
In theory, there is no difference between theory and practice.
In practice, there is. .... Yogi Berra
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