UDP Multicast - viewable by any other customer?
I have a Linode instance running a service utilizing UDP multicast to communicate with other services on the same Linode instance. In the future it may be on a VPN like solution with multiple instances (as expected), but for now it is on one Linode instance. Question - can any other Linode customer use WireShark or any other tool to see my multicast traffic? I am guessing the answer is no, but I want to be 100% certain.
No, Linodes can only see traffic destined for IP addresses assigned to them (with very narrow exceptions made for certain critical functionality like SLAAC, NDP, and DHCP to work); regular IPv4 and IPv6 multicast addresses not associated with SLAAC, NDP, or DHCP would get dropped on the host before reaching the Linode.