NAS-identifier instead of IP-identifier

Hello, I am new to freeradius and need a little help.... We are going to be deploying a bunch of Wireless Routers all over the place and they may have DHCP addresses on them instead of static WAN addresses..When a client associates to our Wireless Router they are redirected to the Radius Server which then creates a secure session onto the internet(WPA etc) Is there a way of identifying the router to our FreeRadius server without having a static IP address on each Router? Cheers Rob