If you have recently bought a Cisco router to use on CenturyLink, you are in luck.
My name is Trevor, I have bought a Cisco 1841 to use on my internet. In order to get it to work on my network; I had to configure a port to use DHCP and get an address from my ISP. I then had to configure NAT to route the network to that port that has DHCP.
COMMANDS FOR THOSE WHO ARE NEW TO THE IOS:
int <WAN port here>
ip address dhcp
ip nat outside
int <LAN port here>
ip address <ip address here>
ip nat inside
exit
ip nat inside source list 1 interface <port here> overload
If you have managed to get it to work, then you need to worry about port forwarding your XBOX or PS4 if you have those, otherwise you could end here.
The following ports for PS4 are:
TCP: 80, 443, 1935, 3478-3480.
UDP: 3478-3479.
The following ports for XBOX ONE are:
TCP: 53, 80, 3074
UDP: 53, 88, 500, 3074, 3544, 4500
