Question : Cisco PIX 515E - Routing on same interface

I'd like to confirm that it's not possible to route in and out of a PIX on the same interface.  

The internal network IP range 10.7.4.0
The internal NIC on the PIX 515E is 10.7.4.1
Default gateway for all the internal clients is 10.7.4.1
On of the machines (10.7.4.21) on the internal network is set up as a RRAS server to link the 10.7.4.0 and 10.7.1.0 networks

Ideally, I'd like PIX to route 10.7.1.0 traffic to 10.7.4.21.

I've added the route to the PIX
I can ping any client on the 10.7.1.0 network from the PIX console - which confirms that the RRAS server is working correctly
I cannot ping any of the clients on 10.7.1.0 from a machine on the 10.7.4.0 network.
My research suggests that you cannot get the PIX to route the traffic in this way, but I wanted a 'second opinion'

Can I solve the problem by putting another interface card in to the PIX and using that instead of the RRAS server?

Answer : Cisco PIX 515E - Routing on same interface

You are correct in that you cannot get packets to go into a PIX and then back out the same interface.

However, you can put another NIC in the PIX to create a third connected network (your first internal, your public, and now your second internal).  You can then set up whatever security you want for it to pass traffic between the two internal networks.

The statement that a PIX cannot route is not truly accurate.  Technically, if you connect both internal networks to different interfaces and configure the security to allow it, the PIX will route between the two networks.