With firewall enabled (and MAC filtering disabled).
For vmbr1 and enp5s0, results are the same :
ping 1.1.1.1 from VM
tcpdump -i enp5s0 icmp
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on enp5s0, link-type EN10MB (Ethernet), snapshot length 262144 bytes...