If your modem is not a modem/router combo, then you will need a separate router since a modem only device will only provide one IP address. A router allows you to connect multiple devices by creating a subnet of private IPs. A switch cannot do this for you.
If you provide make/model of all devices, someone may be able to assist with troubleshooting. A new router probably will provide better performance though.
I have a 100mb down cable internet connection, but I cant connect straight from my modem to my switch, I have to connect from modem, to router (because of something to do with IP) and then from router to my switch and out to the rest of the house.
Why does it not work without the router? The reason I have a problem with this is because my current router is old as **** (linksys) and it only supports 20mb down so I'm getting capped at 1/5th of the speed I'm paying for.
Secondly, the wireless of the router is turned off, I have other wireless points that I use for wi-fi.
Should I just get a gigabit router or can I somehow get this to work without having a router?