Score:0

UDP Broadcast not being masqueraded

in flag

I have a VM in Proxmox with an IP (192.168.1.10) coming from a bridge. I have masquerading on to enable it to communicate with my network:

-A POSTROUTING -s 192.168.1.0/24 -o host_inteface -j MASQUERADE

It works great except with this kind of packet:

WOL packets (UDP port 9) on 192.168.0.255

When using termshark I don't see those packets on the host interface, they seem to have disappeared. I see the other perfectly.

Any idea what I could do ?

Ron Maupin avatar
us flag
Broadcasts cannot be routed, they are only on the local network, so it makes no sense to try to NAT a broadcast.
Catfoxes avatar
in flag
This isn't really helpful, I'm trying to broadcast to the hosts network as the IP targeted is over there, this a legitimate use case, unless the approach is somehow wrong which I'd like to know why.
Ron Maupin avatar
us flag
If you are broadcasting on the same network, there is no need to NAT. Broadcasts cannot be routed, and if it is on the same network, why change the address? In any case, you seem to be trying to broadcast from one network to a different network. `192.168.1.0/24` is a different network than `192.168.0.0/24`. Sending packets from one network to a different network is routing, and broadcasts cannot be routed. Any layer-3 device receiving a broadcast must try to use it for itself, not forward it.
in flag
If you really want to force forward, then you need to create a rule for that. Broadcast is not intended to be routed.
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