I setup a mangle rule to place a routing mark on all traffic
emanating from a specific subnet e.g. 192.168.11.0/24.
Then I used this routing mark in a route to direct this traffic
towards a specific gateway.
I was surprised that I also had to specify a protocol and destination
port n° (e.g. tcp 80) else the traffic wasn't properly routed.
I saw the packet count increment as the traffic was being mangled
but the routing didn't actually occur.
Is there a minimum number of details that one must specify
for the mangling/routing to operate properly ?