Pour avoir la possiblité de supporter plusieurs DHCP Relais (issus du paquet isc-dhcp-relay), il est possible d'adapter le script de lancement ainsi /etc/init.d/isc-dhcp-relay :

#!/bin/sh
#
#

### BEGIN INIT INFO
# Provides:          isc-dhcp-relay
# Required-Start:    $remote_fs $network
# Required-Stop:     $remote_fs $network
# Should-Start:      $local_fs
# Should-Stop:       $local_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: DHCP relay
# Description:       Dynamic Host Configuration Protocol Relay
### END INIT INFO

# It is not safe to start if we don't have a default configuration...
if [ ! -f /etc/default/isc-dhcp-relay ]; then
        echo "/etc/default/isc-dhcp-relay does not exist! - Aborting..."
        echo "Run 'dpkg-reconfigure isc-dhcp-relay' to fix the problem."
        exit 1
fi

case "$1" in
        start)
                for file in `ls /etc/default/isc-dhcp-relay*`; do
                        SERVERS=""
                        INTERFACES=""
                        OPTIONS=""
                        . $file
                        file=`basename $file`
                        echo $file
                        DHCRELAYPID=/var/run/dhcrelay-$file.pid
                        OPTIONS="$OPTIONS -pf $DHCRELAYPID"
                        # Build command line for interfaces (will be passed to dhrelay below.)
                        IFCMD=""
                        if test "$INTERFACES" != ""; then
                                for I in $INTERFACES; do
                                        IFCMD=${IFCMD}"-i "${I}" "
                                done
                        fi
                        start-stop-daemon --start --quiet --pidfile $DHCRELAYPID \
                                --exec /usr/sbin/dhcrelay -- -q $OPTIONS $IFCMD $SERVERS
                        done
                ;;
        stop)
                for file in `ls /etc/default/isc-dhcp-relay*`; do
                        file=`basename $file`
                        echo $file
                        DHCRELAYPID=/var/run/dhcrelay-$file.pid
                                start-stop-daemon --stop --quiet --pidfile $DHCRELAYPID
                done
                ;;
        restart | force-reload)
                $0 stop
                sleep 2
                $0 start
                ;;
        *)
                echo "Usage: /etc/init.d/isc-dhcp-relay {start|stop|restart|force-reload}"
                exit 1
esac

exit 0

Du coup, on peut créer plusieurs fichiers dans /etc/default/isc-dhcp-relay, en mettant une extension différente.