Hi,
So I know IPIP does not support multicast but GRE does. I created a GRE tunnel between a Linux machine and my Mikrotik router.
From the linux end I send packets addressed to 244.0.0.5 (a multicast address). With tcpdump I can clearly see these packets being transmitted.
However, on the Mikrotik side with the packet sniffer, these packets are not received!
How can this be?
Thanks!
Shooting in the dark: check MTU settings of all involved interfaces (the LAN interfaces, bridge and GRE tunnel interface) as well as multicast packet sizes. I’m not sure if ROS fragments multicast packets (I’m guessing it’s not).
Thanks, I have checked this already. GRE tunnel MTU is 1476 on both sides (Linux and Mikrotik).
I have tried setting to a smaller value, like MTU=1200. No changes.
Is there a configuration/mtu with which I can exclude all MTU related issues?
Any more suggestions?
EDIT: I also tried ping to the multicast address. Ping is just 64 bytes. Again, packet shows up in tcpdump but is not received on the mikrotik side.
I guess you need to configure multicast routing on both ends to have multicasts pass the GRE tunnel.