If you use the renewed Oleg's firmware from http://code.google.com/p/wl500g/ inadyn is already installed.

I have done the following steps:

Deactivate the DDNS-Service in the web-interface if it is activated.

Create the config file /opt/etc/inadyn.conf as described in post #1.

If you have set up your router with wengis HOWTO you can do the following to start up inadyn:

Create the file /opt/etc/init.d/S22inadyn
Code:
#!/bin/sh

if [ -n "`pidof inadyn`" ]; then
   /usr/bin/killall inadyn 2>/dev/null
fi

/usr/sbin/inadyn --input_file /opt/etc/inadyn.conf
Make it executable
Code:
chmod +x /opt/etc/init.d/S22inadyn