Redirecting a port with Checkpoint Firewall-1

You can achieve this by using the NAT engine of checkpoint... Something allong these lines should work:

Source            Destination    Protocol    Source     Destination        Protocol
Internal_LAN     Any               http           Any          squid_srv           3128

But wouldn't it be better to just point the client's webbrowser to use the squid as proxy server? Which internet browser are you running?

Kind regards.

But I have a lot of clients and I wanna do a transparent proxy, some clients are out of the city and I can't go there and configurate manually.

Depending on your FW-1 version, this may not work.
Older versions performed the NAT after the OS performed the routing decision. The routing decision is to send the traffic to the Internet, not to the DMZ.

Newer versions solve this problem by performing the NAT on the inbound side, before any routing decision is made. This is enabled by checking the checkbox "Translate destination on client side" under the "Manual NAT rules", in the Global Properties, in the NAT tab. Make sure you check the manual one, not the automatic one.

If you have an older version, and the checkbox doesn't exist on your version, write back and I'll suggest another possible solution.

The checkpoint complains that this is a invalid rule. It says that I can't use the destination ANY on the original packet. I didn't find this checkbox in checkpoint, I think my version is really old. It is 4.1.

What about HTTPS traffic, how can I redirect it?