Creating alerts for dependencies and groups

Hello,

          currently we do not have any groups, so of course when a router or a ISP goes down, we get alerts for every server. So I created a dependency for one router, and assigned it a group (with all the servers that depend on that switch).

I rebooted one server in that group, and still got the old alert (which is good).  but how do i setup the alert for when the router/ISP have an issue, and only send one alert?  Do I have to create an Alert for the router?

thanks for the help