You can use the show traffic command in order to determine how much traffic passes through your PIX. If you have multiple interfaces, the command can help you determine which interfaces send and receive the most data. For PIX appliances with two interfaces, the sum of the inbound and outbound traffic on the outside interface should equal the sum of the inbound and outbound traffic on the inside interface.
If you come close to or reach the rated throughput on one of your interfaces, you need to upgrade to a faster interface or limit the amount of traffic that goes into or out of that interface. Failure to do so can result in dropped packets.
