Cisco Pix

Cisco PIX (Private Internet eXchange) is one of the most popular IP firewalls and network address translation (NAT) appliances.

The PIX is a firewall appliance based on a hardened, specially built operating system, PIX OS, minimizing possible OS-specific security holes.

The PIX runs a custom-written proprietary operating system originally called Finesse (Fast InterNEt Server Executive), but now the software is known simply as PIX OS. It is classified as a network layer firewall with stateful inspection, although technically the PIX would more precisely be called a Layer 4, or Transport Layer Firewall, as its access is not restricted to Network Layer routing, but socket based connections (a port and an IP Address - Port communications occur at Layer 4).

PIX firewalls provide a wide range of security and networking services including:

Network Address Translation (NAT) or Port Address Translation (PAT)
content filtering (Java/ActiveX)
URL filtering
IPsec VPN
support for leading X.509 PKI solutions
DHCP client/server
PPPoE support
advanced security services for multimedia applications and protocols including Voice over IP (VoIP), H.323, SIP, Skinny and Microsoft NetMeeting
AAA (RADIUS/TACACS+) integration