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Old 08-28-2007, 09:02 AM   #1
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DNS Master Zone Vs. DNS Slave Zone

If I setup a dns server and a slave zone to that master server. Does that mean that if the primary server goes down the slave server will be able to respond to DNS queries ?
Old 08-28-2007, 09:16 AM   #2
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I believe so... This is the whole point of 2 servers having duplicate info. If one of them dies the other is capable of taking over the other's job. Redundancy
Old 08-28-2007, 11:53 AM   #3
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yes, presuming:

- the world knows about your secondary. That is, you have to go to the domain registrars, or your parent DNS zone, and make sure your secondary is listed as a name server on each domain. to wit: check the NS records on each domain to make sure secondary is listed, 'dig ns foo.domain @your.primary.server.ip'.

- your secondary believes it is authoritative for each zone. If it's not configured to believe it's auth, then it will eventually honor the time-to-live expiration your master has set in the zone. So, for example, it will work fine for like 12 hours, then suddenly the slave decides it doesn't trust the cached data and your secondary stops answering. to wit, check a 'dig soa foo.domain @your.secondary.server.ip' and make sure the "aa" flag (authoritative answer) is present in the response.

Caution: your primary is not "preferred" over the secondary in the DNS architecture. If you stand up a secondary, it must be able always answer as quickly as the primary. If you get a slow/sucky server into the NS records mix, you get weird issues when random-DNS-query-from-public goes to the secondary. The secondary is NOT just used if the primary fails. All listed DNS servers are used all the time.


Last edited by cconstantine; 08-28-2007 at 11:55 AM.
Old 08-29-2007, 09:28 AM   #4
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Thanks for the info...that is what I needed to know ..I did the DIG and I did not get an AA in the answer..what should I do to change that ?

I got an aa as presented in the line below but I do not think that this is the AA you meant..or am I wrong ?
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

Last edited by ALInux; 08-29-2007 at 09:30 AM. Reason: Updated Info


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