Time Warner/Road Runner is offering me a connection to the Internet
through an RCA cable modem, Model DCM425:

http://www.speedtouch.ca/pdf/dcm425_4.pdf

The thing has only two connection ports, one is a USB and the other
one for an Ethernet RJ45 cable

I need to connect the only Ethernet port from the cable modem to a TP-
LINK TL-WR642G router

After noticing some problems I thought the two routers where
conflicting, so I changed the internal IP of the TP-LINK to
192.168.2.1, but I cannot still connect to the Internet

What am I missing?

Could my ISP check that there are connections from other MAC
addresses and block them?

What should I do to fix this problem?

Thank you
lbrtchx