Redundant data in zone file.
Bill Larson
wllarso at swcp.com
Tue Nov 16 21:33:19 UTC 2004
On Nov 16, 2004, at 11:31 AM, SilentRage wrote:
> With similar domains that share dns records, I certainly do specify
> multiple zone {} blocks in named.conf that refer to the same file.
> You just have to be careful to never explicitly indicate any one of
> the domains that use that file. Use nothing but relative hosts and
> '@' to refer to the zone name. Sure makes updating all three zones
> much easier.
Although this is good advice, it isn't exactly correct either. Some
DNS information, such as the target of an MX record, the SOA record,
and the NS records may need (maybe "should") be fully qualified. For
example, as a generic zone file for multiple zones where "domain1.com"
is your "primary" domain name, you could have:
$TTL 86400
@ IN SOA ns1.domain1.com. hostmaster.domain1.com. (
1; Serial
28800; Refresh
14400; Retry
3600000; Expire
86400 ); MinTTL
; delegated DNS servers for zone
IN NS ns1.domain1.com.
IN NS ns2.domain1.com.
; Mail Exchanger info for zone
IN MX 10 mail.domain1.com.
; Host information
ns1 IN A 1.2.3.4
ns2 IN A 1.2.3.5
; Web server for domain
www IN A 1.2.3.10
For zones "domain1.com", "domain2.com", and "domain3.com", you would
end up with the following "A" record information defined:
ns1.domain1.com IN A 1.2.3.4
ns1.domain2.com IN A 1.2.3.4
ns1.domain3.com IN A 1.2.3.4
ns2.domain1.com IN A 1.2.3.5
ns2.domain2.com IN A 1.2.3.5
ns2.domain3.com IN A 1.2.3.5
So, each zone would have an "ns1" and an "ns2" host identified, and
they would all point to the IP addresses of the DNS servers, but the
actual name servers for each of the zones would actually be
"ns1.domain1.com" and "ns2.domain1.com" as defined by your "NS"
records. Don't confuse the "ns*" name with the identification of the
delegated server.
More telling would be the "A" record for the "www" host. These fully
qualified domain names would be:
www.domain1.com IN A 1.2.3.10
www.domain2.com IN A 1.2.3.10
www.domain3.com IN A 1.2.3.10
So, accessing "http://www.domain*.com" would always get you to the same
server by IP address. Now, by setting up virtual domains on the web
server, you could have each of these names return different
information. At a minimum, the URL information returned could be
specific to the web site address given. I.e., "www.domain1.com" would
return that you are accessing domain1, and "www.domain2.com" would be
for "domain2". If you do NOT configure this virtual domain info for
your web server, then everything would report back to the user as if it
were for "domain1". (The same thing would also occur if you got to the
web server by it's IP address, no name in the URL. The returned
information goes back to the user as if it were for the "primary"
domain that the server is set up for.)
So, you can, and should, have a mixture of fully qualified domain
information and partially qualified domain information in your zone
file when you are creating a common zone file for multiple domains.
Bill Larson
> Dave
>
> --- Reply to: bob prohaska <bp at fib.eecs.berkeley.edu> ---
>>
>> Is there any harm in having redundant information in zone files?
>>
>> For example, I've registered three domains:
>> zefox.com
>> zefox.net
>> zefox.org
>>
>> They must share 5 ip addresses: one for each nameserver in .net
>> and one for each www.zefox.com/net/org address. The netblock is
>> 64.161.5.105-109.
>>
>> Will errors result if a zone file contains A records for hosts
>> in a different zone? It would simplify matters of all could share
>> the same zone file, but clearly that can't go on forever, if at all.
>>
>> Thanks for reading, and your help so far!
>>
>> bob prohaska
>>
>>
>>
>>
>
>
>
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