DNS Serial Numbers

[Scott Caporale]

How many numbers is the Serial number for a DNS database file limited to?

We are using the convention of yymmddhhmm for our serial number, However the leading 0 does not get passed down to our secondaries. When we use the format yyymmddhhmm. Our secondaries come up with a new serial number altogether.

[Tim Malnati]

RFC1034 states that the serial is a 32 bit integer which limits it to 9-1/2 digits if I'm doing my conversions right. Who knows how bind is actually handling out of range situations though.

[James A. Donovan]

I use yyyymmddXX where XX simply represents the revision number of that file for that day, and that works for me. I've never had to revise a DNS file more than 99 times in one day.

[Bruce Regittko_1]

Hi,

If the number is a 32 bit signed value, the maximum it can be is 2 ^ 31 - 1 or 2,147,483,647. Thus, the yyyymmddXX format will work for a few more years.

BTW, if it is an unsigned value, the maximum value is roughly doubled, which will be good for a good bit longer.

--Bruce

[Matts Kallioniemi]

What do you mean by "yyymmddhhmm"? If you're using the last three digits of the current year or the last two digits you should come up with the same value since 001 == 01.

Don't worry about leading zeros, they are not significant.

The largest serial number is 4,294,967,295. Be careful when you go into the billions though, because 4,000,000,000 is actually *smaller* than 2,000,000,000 since the comparison is done using sequence space arithmetic.

You should really pick up a copy of DNS&BIND. It is a must read for every DNS admin.

Matts

[Matts Kallioniemi]

What I really meant was:

4,000,000,000 is actually *smaller* than 1,000,000,000

(sequence space arithmetic is hard...)

[Shannon Petry]

Noone mentioned the omition of 00 from 00102015501...

In most cases, the actual numbers are stripped to their "real" form so
00102015501 is really
102015501 when read by secondaries or other applications reading the SOA header.

It should be relatively easy though to have secondaries get info if there is a "different" serial number (I'm pretty sure this is the default mechanism.)
So at this point as long as your serial number is different, maps are transferred anyway.
I.E. Last serial number x-fered from secondary. "1001001". SOA reports a serial number of "1002" so the secondary transfers the zone anyway. :)

Regards,
Shannon