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Allowed third party company connect via Cisco PIX 501 safely

I am new in the firewall and router setting and configuration.
The current setting is done by a third party company and now I am trying to do it myself to meet the new requirement.
The current scenario is:

In my main office, I have 2 routers (Router 805), 2 leased lines and 1 Cisco Pix 501 firewall. And in my branch office, I have 1 router (Router 805).
In the main office, the 2 routers are connected to firewall and then the firewall is connected to 3Com 12 ports 10/100 switch. 1 of the router is connected to the Internet and another 1 (Router A) is connected to branch office router (Router B).
The IP address of the firewall in main office is
The gateway of the users in main office is (Router A) and the gateway of the users in branch office is (Router B).

Now, my main office has a 3rd leased line to connect to a third party company and thus have a 3rd router as well.
But, I don’t know how to connect to my current network securely because my friend told me that the Cisco Pix 501 firewall has 4 ports and the 4 ports are trusted.
Thus, it is not safe if I just put in the 3rd router to the 3rd port on the firewall.
Any suggestion of the new requirement?
The purpose of the 3rd leased line is for some of my users to use the third party company web base software to key in sales order and the information is stored in the third party company.
The users will click the printing button to print but the printing command is sent from the third party company to my print server.
So, for outgoing port, I need to open TCP 80 and for incoming, I need to open few ports (I don’t know what ports to open yet) to accept the printing command from the third party company IP Address (few IP addresses).
And some users who need to access this web base software also have Internet access.

Any suggestion or help are appreciated.
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1 Solution
You have two options (as I see it):

1. Put the new connection on the untrusted (outside) of your PIX, then setup some static NAT translations (with ACL's) to permit the print traffic back to your printers.

2. Put the connection on the trusted (inside) of your PIX. If you were to do this, then you would need to have control of the router on your end and secure it in a fashion that you would be comfortable with. Essentially, you would do the same as if you were using the PIX. Allow ONLY HTTP outbound and printing back inbound.

The first choice may not be an option if you don't have any spare IP addresses that are in the subnet that your PIX outside interface is in. Security wise, the better option is possibly the first one, but they are much the same as either way you would be allowing the print traffic from an "unknown" source back into your network (which as long as you limit it appropriately is quite acceptable).

The 4 ports of the firewall are all identical. It is simply a four-port switch that is built in to the PIX. The PIX 501 only has two interfaces, one "inside" and one "outside".
NaughtygalAuthor Commented:
Hi td_miles!
Thanks for the prompt reply.
The IP address of the external interface of the PIX is assigned by the ISP.

Will it be safer and better if I get a new firewall to replace the current one?
If so, any suggestion (brand, model etc) on the new firewall?

>  Will it be safer and better if I get a new firewall to replace the current one?

Not necessarily. If you choose to use a router that is connected to you internal network, as long as it is configured correctly, the risk will essentially be the same.

The key to security is to explicitly permit only the traffic that you require and block everything else.

> If so, any suggestion (brand, model etc) on the new firewall?

I would advise you to stick with Cisco PIX. To gain 3 interfaces, you would need to purchase the PIX 515 DMZ bundle. When you look up the price for this, you may decide to go with an internal router for this connection ;)  Just make sure it is a Cisco router and that you have administrative control over it so that you can configure it as required.
NaughtygalAuthor Commented:
Hi td_miles!
Thanks for your reply.
Em.............The problem is, I only have control on the 2 existing routers in the main office and for the 3rd new router which is in my main office and connected to the third party company, is controlled by the third party company and their vendor. :(

So, that means my only choice is to get a new firewall, right?
Em.......Except Cisco, any suggestion on other brand firewall? Because I would like to configure the firewall and control it myself.
So, I would like to get support directly from the company and if I get the Cisco firewall, I cannot get any support from Cisco because if I call or email Cisco, they will "ask" me to contact an authorised vendor.

Thanks for the help and sorry for the trouble..........
NaughtygalAuthor Commented:
I have decided to get a Watchguard firewall for my company.
Although my solution is not td_miles answer but he answered my question correctly and thus I accept his answer.
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