I have discovered a wired behavior on my VyOS setup.
First I’ve seen that MTR and Traceroute don’t work.
I’ve tried to manually send a ICMP request with a low TTL so see if I get a response.
But nope, VyOS seems to either just ignore it or is unable to send me the answer.
The same behavior also happens, for internal routes between VLANs.
So for example
VLAN100-Client (172.20.100.50) -> VyOS (172.20.100.1 / 172.20.30.1) -> VLAN104-Client (172.20.30.103)
In this example there is no firewall or NAT involved. Just plain routing where VyOS acts as a gateway.