Chromecast and other broadcast or multicast-based apps have not been supported since late 2014 because they could contribute to wireless performance issues (helpdesk ticket 64415/62645).
Run Google's Chromecast setup program and obtain the Chromecast MAC address. It might take a few minutes for it to appear. You will not be able to do anything else with the setup program until the rest of the steps below are completed. Enter the Chromecast MAC address into https://connect.carleton.edu/device-registration An administrator of PacketFence/connect.carleton.edu must put the Chromecast into the same Role as your other devices land in, which is usually but not always OPENCARL. This must be the Role, not the "bypass" VLAN. The "guest" and "browserless" categories restrict the device to the 188-191 network, where the controlling laptop or smartphone will be unable to find it. Chromecast does not currently support WPA2-Enterprise, so both the Chromecast and any devices connecting to it must be on the Carleton Guest network. Chromecast cannot extend beyond its local network, so the laptop or smartphone source must also be connected to Carleton Guest, and registered by the same user ("PID" in PacketFence terms). I had to add an Aruba firewall rule to permit SSDP: destination 126.96.36.199 on UDP port 1900. This is a permanent change, noted here for my own reference only. When your laptop is on the Carleton Guest network, there is no privacy/security for your network traffic. Performance is poor because the Chromecast only supports 2.4GHz, while your laptop will probably be on 5GHz. The 2.4GHz band is adequate in a private home environment with only one radio, but it's too slow in a dorm with many radios. Also, use of the Chromecast will noticeably slow the connection of anyone else in radio range. There is absolutely no access control. Any registered user of the Carleton Guest network can view and change what's on your TV without your knowledge. (AppleTV might be a bit better in this regard.)