Yes, you can augment a pool of global addresses with PAT. When all IP addresses from the global pool are in use, the PIX will begin to use a single IP address that you set up in a second global command. Just make sure that it does not overlap with ad...
You've probably already tried the Command Reference, but it's probably the best thing to go to.http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_62/cmdref/ab.htm#xtocid7
