To locate the IP address and MAC address for your Chromecast, open the Google Home app on an Android phone or tablet, iPhone or iPad.
After opening the app, follow these instructions:
1. Open the app, then tap the desired Chromecast
2. Tap the gear icon/menu button for your device — It's located at the upper right of the device screen
3. Scroll to the bottom of the displayed page.
The IP address and MAC address are located at the bottom of this screen.