Why do packets go in one case, and not in the second?

Question

Mikrotik

Hello.

/ip firewall mangle
add action=mark-connection chain=prerouting new-connection-mark=Test-conn \
    passthrough=yes
add action=mark-routing chain=prerouting connection-mark=Test-conn \
    new-routing-mark=to-gre passthrough=yes src-address=192.168.100.0/24

/ip firewall mangle
add action=mark-connection chain=prerouting new-connection-mark=Test-conn \
    passthrough=yes src-address=192.168.100.0/24
add action=mark-routing chain=prerouting connection-mark=Test-conn \
    new-routing-mark=to-gre passthrough=yes

The second option, with the src-address in the connection mark, does not allow traffic. It is not available on clients.
But as soon as you transfer the address to the route marking, everything starts working.

Isn't that oil?

Answer 1

https://wiki.mikrotik.com/wiki/Manual:IP/Firewall/...
Fortunately if connection tracking is enabled, we can use connection marks to optimize our setup.