May be not often but still you may need to configure static nat for some purpose like this;

Say; You want to map;

1.1.1.1 -> 10.20.30.40

2.2.2.2 -> 10.20.30.40

On a PIX/ASA firewall this would not be allowed to be configured, so how do you overcome this restriction ?

Assuming that 10.20.30.40 is a windows machine, you could assign more than 1 ip address (upto 5) on a same interface card. So assign one more ip address on the NIC, call it 10.20.30.50 and map it to the other public ip address.

How to add this into a windows machine ? Read Here….

Then go on to the PIX, add these;

static (inside,outside) 1.1.1.1 10.20.30.40 netmask 255.255.255.255

static (inside,outside) 2.2.2.2 10.20.30.50 netmask 255.255.255.255