Wireless help request

[Jean-Paul Thuot]

I apologize for this semi-off topic request.

I have recently purchased a wireless access point (not a router) to go 
with my new airport card.  I plugged the access point into my router, 
fired up the airport and voila I was surfing wireless.

However, I like to be a responsible network admin, so I'd like to lock 
this wireless LAN down.  The manual says the default IP address of the 
access point is 192.168.1.100, but the router's internal address is 
192.168.123.xxx, and thus computers connecting to this router are given 
IP addresses in this range.  Therefore the access point cannot have the 
default address, but so far I have been unable to discover the IP 
address of it.

Ifconfig on this ibook gives me an IP address of 192.168.123.xxx, and 
the gateway IP is that of the router (not the access point).

The user's manual is less than useful in this regard as it doesn't give 
any other option than the default.  Is there some way I can sniff out 
the access point's IP address?

I thank you in advance.

Jean-Paul