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Dynamic Updates by the Client

I have assumed that the DHCP server would do the DNS updates. Of course it does not have to, and indeed, on a limited scale it might be easier to do on the client's server. Doing it from the DHCP server gives low ACL/key maintenance overhead and, if need be, full control of what gets added. But there is nothing stopping you from giving the DHCP (or PPP) client access to update DNS. By running a simple script after the interface has been assigned, an address DNS can be updated:

#!/bin/sh

PATH=/sbin:/usr/sbin:/bin:/usr/bin
export PATH

IF=hme0
NAME=gentoo.dyn.penguin.bv
TTL=60

IP=´ifconfig $IF | awk '/inet/ { print $2; }'´

nsupdate <<EOC
update delete $NAME
update add $NAME $TTL A $IP

EOC

The script shown here works on Solaris. It needs to be adapted to other OSes; the interface names and the output of ifconfig vary wildly between OSes. Also add the -k option if you want to use TSIG signing.

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