Cannot connect to gateway when dhcp server down in windows AD?

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http://serverfault.com – I have 2 AD servers conncted to a netgear fvx538. The servers have DNS and DHCP roles as usual, but are currently shutdown for power maintenance. Even so, I expect that if I connect a client laptop directly to the firewall, I will still be able to access its web interface and Internet. But this is not happening. Is this suppose to be the case that I need the AD servers up? Or you think my firewall gone bonkers? I power off and on the firewall but still not getting ping response from it. Multiple laptops connected this way are able to see each other so the switch an routers are working. (HowTos)