Using A Router As Switch / Hub?

I have this ARRIS router from Comcast that actually blocks some ports, so I can't use certain programs. I noticed this cause when I played this game, Ragnarok Online, I googled that it needs to open certain ports for me to login. Another would be my CoD, where I need to open some ports to join certain games.

Then I told my roommate that we need more LAN ports for our xbox, ps3 and TV. So we used this old router as a switch. At first, we used 1 of 4 LAN ports of the ARRIS Comcast router to the "Internet" port of the old router, so we thought we would have 4 more LAN ports provided by the old router. First day, it actually worked, and I was surprised that some sites aren't blocked, and I can login to Ragnarok Online. After some time, it stopped working, so I googled it then it says I have to Disable DHCP, use an IP address that's not used by the ARRIS router, then plug in the cable to 1 of the 4 LAN ports of the old router, not the "Internet" port. I did, then it worked again.

It did work as a switch, but how come it worked before where no sites/ports are blocked?To sum it all up, is there a way to make the switch (old router) work when I plugged the cable on the "Internet" port?