When I studied for the CCNA, I learned which devices should be connected using a straight through cable and which using a crossover cable. For example take this explanation for question one from a study site.
Group 1: Router, Host(PC), Server
Group 2: Hub, Switch
One device in group 1 + One device in group 2: use straight-through cable
Two devices in the same group: use crossover cable
Based on this I should use a crossover cable between a router and PC.
But, I have an Internet connection with a DSL router. In this scenario I'm using a straight through cable between my router and PC.
So this has me confused, why can I use a straight through cable between my DSL router and PC?