Port address translation (PAT) is a function that allows multiple users within a private network to make use of a minimal number of IP addresses. Its basic function is to share a single IP public address between multiple clients who need to use the Internet publicly. It is an extension of network address translation (NAT).Port address translation is also known as overload or port overload.
Static Network Address Translation (NAT) works in PIX Firewall version 6.3(1). However, global Port Address Translation (PAT) does not work properly.
When the PIX configuration is changed to use global PAT, all Telnet and Secure Shell (SSH) connections fail.
Note: Even the clear xlate command does not resolve the issue.
For a workaround, upgrade the PIX software to version 6.3(3) or later.