I have 50 users in my environment who all translate to a single public IP address using NAT overload on a pix 515. Usually when testing throughput on speedtest.net, my users were getting 80mb down and 70mb up. A few days ago i noticed that the numbers dropped significantly to 35/25. I was able to narrow down the problem to pix nat overload function by assigning a static one to one address to an inside client and the clients speed were restored to 80/70. I checked xlate and found aprox. 600 translations - after doing clear xlate , the problem did not resolve. I am stumped and appreciate anyone jumping on this.