Comment 9 for bug 90267

ntp ought to be restarted when a new interface is brought up, but for some reason this is disabled by default:

mizar:[/etc/network/if-up.d] cat ntp
#!/bin/sh

# remove (or comment out) the next line if your network addresses change
exit 0
case $ADDRFAM in
        inet*)
                if [ -x "/etc/init.d/ntp" ]; then
                        if [ -x "`which invoke-rc.d 2>/dev/null`" ]; then
                                invoke-rc.d ntp restart || exit $?
                        else
                                /etc/init.d/ntp restart || exit $?
                        fi
                fi
                ;;
esac