Esse vai para os colegas que não conseguiram fazer funcionar na versão 2.9.27.
/ ip firewall mangle
add chain=output protocol=tcp src-port=3128 content="X-Cache: HIT" action=mark-connection new-connection-mark=squid-connection-HIT passthrough=yes \
comment="Cache-squid" disabled=no
add chain=output connection-mark=squid-connection-HIT action=mark-packet new-packet-mark=squid-packet-HIT passthrough=no comment="" disabled=no
add chain=prerouting in-interface=Cliente src-address=172.16.0.0/16 action=mark-packet new-packet-mark=test-up passthrough=no comment="UP TRAFFIC" \
disabled=no
add chain=forward src-address=172.16.0.0/16 action=mark-connection new-connection-mark=test-conn passthrough=yes comment="CONN-MARK" disabled=no
add chain=forward in-interface=Link internet connection-mark=test-conn action=mark-packet new-packet-mark=test-down passthrough=no comment="DOWN-DIRECT \
CONNECTION" disabled=no
add chain=output out-interface=Cliente dst-address=172.16.0.0/16 action=mark-packet new-packet-mark=test-down passthrough=no comment="DOWN-VIA PROXY
disabled=no
/ queue tree
add name="downstream" parent=Cliente packet-mark=test-down limit-at=1024000 queue=default priority=1 max-limit=1024000 burst-limit=0 burst-threshold=0 \
burst-time=0s disabled=no
add name="upstream" parent=global-in packet-mark=test-up limit-at=512000 queue=default priority=1 max-limit=512000 burst-limit=0 burst-threshold=0 \
burst-time=0s disabled=no
add name="Cache-full" parent=global-out packet-mark=squid-packet-HIT limit-at=2000000 queue=default priority=8 max-limit=2000000 burst-limit=0 \
burst-threshold=0 burst-time=0s disabled=no