On the machine you want to log to (i have a slackware one):
root[floyd]# nano /etc/rc.d/rc.syslog
replace:
echo -n "/usr/sbin/syslogd"/usr/sbin/syslogd
with:
echo -n "/usr/sbin/syslogd -r "/usr/sbin/syslogd -r
Restart syslog:
root[floyd]# /etc/rc.d/rc.syslog restart
Starting sysklogd daemons: /usr/sbin/syslogd -r /usr/sbin/klogd -c 3 -x
root[floyd]#
After that, all you have to do is: Login to dd-wrt (e.g. http://192.168.2.1/ - please replace with actual IP fof your wireless router ) Go to Services -> System Log -> Syslogd -> Enable Also specify the IP address of the logging server.
On the logging server itself, remember to put some kind of filtering, to prevent any other device to log to it. I'd go for iptables.