I have a Cisco 1841 connected to the Internet with public IP address. I have a PC connected to the Fa port of the router. The block of IP address for the LAN is a public block. My PC cannot access the Internet. I am not sure why as I have a default route (ip route 0.0.0.0 0.0.0.0 ISP_IP_address) pointed to the ISP WAN port.