How to use external open source caching server

AOA

some time admin want to control users http requests throw costmized ACL's or other scripts,

i am using mikrotik as a pppoe server, all pppoe or 192.168.0.0/23 network clints are conect with mikrotik directly throw LAN,

my mikrotik with 3 LAN Cards

1) LAN (for clints)

2) WAN (for internet)

3) eth1 (for squid)

squid have 2 type of networks

1) LAN IP Address 192.168.100.1/24 without any gateway or route address

just for LAN conectivity with mikrotik eth1 with 192.168.100.2/24 IP Address

2) PPPoE conection for internet throw mikrotik 'but' difrant IP Address 192.168.12.2 (normal clints IP address 192.168.0.0/23)