Originally Posted by
Blorgin
Can you explain your setup a bit better? Is your computer you're streaming from on the same physical network as your chromecast? And your computer connected to a VPN? If this is the case you're likely using 'split tunneling', your VPN knows what your local subnet is and won't try to tunnel traffic to it.
For example your home network is 192.168.0.0/24, your computer has 192.168.0.10 and chromecast 192.168.0.11. Your VPN client might 'know' that your local network is 192.168.0.0/24 so it won't tunnel traffic destined to that network and your chromecast will see the traffic coming from 192.168.0.10, not the 'source address' of your VPN
Hopefully this helps