Question : ip address conflict (Help)

home for the holidays trying to configure my parents computers. They have Yahoo SBC DSL service
my father is a teacher and bought a router home from school to use in the house. the router is a linksys huge 24 ethernet port/socket used in computer labs.

so i ran the DSL thought the router and connected 1 computer to it. that worked fine but when i connected a 2nd computer to it this message keeps poppin up on both computers: there is a ip adress conflict with another system on the network

when both computers are conntected to the router the internet does not work on either computers.
is there anyway to correct this problem.

only 2 computers will be connected to the router

Answer : ip address conflict (Help)

Yeah, there's your problem. Most likely your ISP is only allowing one IP address for your account. You need a router that does NAT.