How do I determine if my router is causing a Steam connection issue? How do I configure my router to work with Steam?
It may seem obvious, but it's worth rebooting your modem, router, or modem/router combination device before trying anything else.
If your modem and router (or wireless access point) are separate devices, test with a direct connection to your modem:
If you are able to connect to Steam after bypassing your router, it indicates a router configuration or compatibility issue.
Certain router services can cause problems with Steam. If any of the following services are enabled on your router or access point, try disabling them:
All required ports to run the Steam application are listed here. It is possible that other games available on Steam will require further ports to be available.