always_on.sh script in DD-WRT not working

Hi folks,

I have a odd problem with always_on.sh script. But first some
background, my setup is this:

<internet>--<Half Bridge ADSL mdm>---<DD-WRT>--<PC's>

The problem is that when my modem disconnects, and subsequently
reconnects (which happens in the space of a few seconds) the script is
not detecting the new IP and therefore not running renew DHCP.

With my very basic skills, i have worked out that, for some reason
after the modem disconnects and reconnects, I can still ping the old
gateway address, yet I cant ping google (IP or name).

I looked closer at what the DD-WRT is getting from my modem in half
bridge:

WAN Config
IP Address : 118.92.137.122
Subnet mask : 255.255.255.255
Gateway : 118.92.137.122
DNS1 : 203.109.129.67
DNS2 : 203.109.129.68

Notice how the Ip Address and the gateway are the same? I am not sure
if they are the meant to be the same, but I think that is why the
always on script (which tests if the connection is up by pinging the
gateway) can still ping the gateway, even if the modem has since
disconnected and got a new IP.

Does anyone know if (a) I have screwed something up or (b) its
behaving this way by design?

The script:

http://www.dd-wrt.com/wiki/index.php...lways_on.sh.29

LAN Setup
MAC Address00:06:25:C4:81:EF
IP Address192.168.1.1
Subnet Mask255.255.255.0
Gateway0.0.0.0
Local DNS0.0.0.0


WAN Connection Type : Auto Config - DHCP

Router Name : DD-WRT
Host Name : Geek
Domain Name :

Router IP
Local Address : 192.168.1.1
Subnet: 255.255.255.0
Gateway: 0.0.0.0
Local DNS: 0.0.0.0

Network Address Server Settings (DHCP)
DHCp Type : DHCP Server
DHCP Server : Enable
Start IP Address : 192.168.1.100
Static DNS1: 203.109.129.67
Static DNS2: 203.109.129.68

If anyone who can help needs more info please just ask!!! :D

Thanks in advance,

-Al
PS: And yes I could just make the script ping one of the DNS servers,
but I would like to know why its not working the way its designed!?

:D :D :D