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Strange Serial Numbers

I have a strange fact I didn't understand, when creating those DNS domains files at /var/named directory.

I have a Script who generates those small files, and in the Serial info it composes a number who is formed by:

YYYYMMDDhhmmss

Well, it works without problem, with one exception: it generates a Serial number in the file, but when we nslookup the Domain, it shows another Serial number.

Please, try this domain:

nslookup -type=Soa areadeteste.com.br 200.201.129.12

It returns the Serial Number 364478947 but inside the areadeteste.com.br DNS file, the Serial number is 20010617111011.

When I used as Serial a number with less digits, the nslookup showed the right number.

Questions:

. Is there a limitation in the lenght of the Serial Number? Could it be the reason?

. Where does it take the other Serial number from?

. Any idea about the problem?

Thanks a lot.

Mario Lima./
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multisites
Asked:
multisites
  • 2
1 Solution
 
vsamtaniCommented:
The serial number in the zone file has to fit in 4 bytes, ie it can be minimum 0 and maximum (2^32)-1 = 4294967296. The usual way of specifying zone file serial numbers is to use

YYYYMMDDnn

where nn is a counter for that day.

The bogus serial number 364478947 is the result of trying to interpet the too-long serial number in the zone file:

20010617111011 mod (2^32) = 364478947

Vijay
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multisitesAuthor Commented:
Yeah, that's it. I will find another way, maybe taking out the century part of the year. Thanks a lot.
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vsamtaniCommented:
You're welcome, and glad to have helped. I would recommend that you keep the century part of the year for your serial numbers, and instead drop the minutes and seconds.

YYYYMMDDnn is a de-facto standard for serial numbers of SOA records, and 2001061711 (1100 hrs, 17 June 2001) is a perfectly acceptable serial number.

Vijay
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