configuring router/AP

I have a Buffalo HP-G54 router. Right out of the box, I connected my
notebook to it using its LAN port. It's default mode is router, so my
notebook got an IP address from it and can config it using its router IP
192.168.11.1. Without unplug anything, I can switch it to AP mode and can
config it using its AP IP 192.168.11.100. With it remain in AP mode, if I
switch it off or unplug the LAN cable or reboot the notebook, i.e. the
notebook loses the IP address acquired from it when it was a router, then I
can't access both config IP.

The only thing I can do then is to hard reset it so that it return to router
mode and gives an IP address to my notebook, then I can config it again. Is
this a normal way to do it? Or there is a better method?