Serial number 0

[Barry Margolin]

We run slave DNS for many of our customers.  Occasionally they mess up
their serial number sequencing, usually by inserting an extra digit and
later trying to fix it by removing the digit; that doesn't work properly,
because the slave server complains that the new serial number is less than
what it has.

The DNS & BIND book, on p.137, says that if the slave servers are running
BIND 4.9 or higher, you can resynchronize by setting the serial number on
the primary server to 0; it says that serial number 0 is treated specially,
and forces a zone transfer every time the slave checks.

Usually this works, but occasionally we see the following message in our
log:

named-xfer[26376]: serial from [<primary addr>], zone <domain>: 0 lower than current: 2000111900

Is this trick really supposed to work?  I looked in the BIND source, and it
looks like it triggers named to fire off named-xfer, but named-xfer doesn't
have any special processing of serial 0 from the master.  I suspect that
this only worked in cases where the serial number that they were trying to
reset from was > 2^31, so that 0 was higher than it in serial number
arithmetic.

So is this trick supposed to work, or are we going to have to labor through
teaching our customers how to perform real serial number arithmetic to
start their serial number sequences over?

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.