UDP Broadcast Relay and subnet-directed broadcasts

kesawi

I'm attempting to use UDP Broadcast Relay to relay multicast announcement packets from my Roborock vacuum cleaner between my IOT VLAN and LAN VLAN.

I can see that the vacuum is broadcasting to the local IOT subnet on 58866 when I use tcpdump -i vtnet0.15 'udp and dst port 58866' -n.

11:11:52.036119 IP 192.168.15.66.39171 > 192.168.15.255.58866: UDP, length 85
11:11:57.036200 IP 192.168.15.66.48544 > 192.168.15.255.58866: UDP, length 85
11:12:02.036152 IP 192.168.15.66.51777 > 192.168.15.255.58866: UDP, length 85
11:12:07.037512 IP 192.168.15.66.36002 > 192.168.15.255.58866: UDP, length 85
11:12:12.036297 IP 192.168.15.66.36779 > 192.168.15.255.58866: UDP, length 85

I've enabled the following setting:

However, when I check my LAN VLAN using tcpdump -i vtnet0.2 'udp and dst port 58866' -n I don't see any broadcast traffic on 58866 and it appears that it isn't being relayed.

Does UDP Broadcast Relay, only relay global broadcasts (i.e 255.255.255.255) and not subnet-directed broadcast (e.g. 192.168.15.255)?

keyser

While I'm not 100% sure it cannot be brought to relay subnet-directed broadcast, it would make little network sense if it did.

Remember that any IP stack on the other side that follows IP guidelinies would still drop the packet even if the NIC picked up the L2 broadcast frame from the wire.

The idea of the package is forwarding Class D (multicast) and proper global broadcast frames.