GRE Tunnel Key

Hello Alex

GRE tunnels by definition support multicast traffic. This is why GRE is often used to convey multicast traffic over a network that may natively not support it. This is useful also for routing protocols to function since they extensively use multicast to operate. The use of a tunnel key does not affect this support of multicast, so yes, you should be able to transmit multicast traffic over GRE tunnels that use a tunnel key.

As for the two GRE tunnels in your lab, there’s really no reason for only one tunnel to be functional at any time. I’m inclined to believe that the problem lies elsewhere. I suggest you start off by recreating the lab in the lesson, with two tunnels that support IPv4. Make sure you get both tunnels to work. Then, go on to changing one of the tunnels to support IPv6. The following lesson will help you to do that:

Check out the behaviour at this point and let us know how you come along. If you have trouble along the way, let us know so we can help you further.

I hope this has been helpful!