The master router is not supposed to be connected until the end of the set up. At least thats what it said on this stickyhttp://www.tomshardware.com/forum/33700-42-ultimate-modem-router-setup-thread
Soooo????? Can I still set it up even tho the master is hooked up?
Yes. The poster that wrote that was assuming a brand new setup. Honestly, I tend to disagree with the original poster in the order. The thing that is mostly important is that the routers are configured independently such that the master doesn't issue the slave router's IP address out, and that the slave router's DHCP server is disabled.
Only after both routers are configured, should you physically connect the ethernet cable from the master, to slave routers...