My Organization is using PAT (port addrees translation) which is easier since all users are using one public IP; (and ofcourse cisco pix firewall 525 series)
nat (inside) 1 10.0.0.0 255.0.0.0 0 0
ip address outside 211.x.x.x 255.255.254.0
ip address inside 10.101.2.10 255.255.255.0
outside 0.0.0.0 0.0.0.0 211.x.x.x 1 OTHER static
inside 10.0.0.0 255.0.0.0 10.101.2.2 1 OTHER static
global (outside) 1 211.x.x.x netmask 255.255.255.254
By using the configuration above, all 10.0.0.0 hosts will be translated to the global address 211.x.x.x.
All source ports will be changed will be changed to a unique port number greater than 1024.
Example: Issue command sho xlate [ENTER}
PAT Global 211.x.x.x(25356) Local 10.23.2.76(1416)
PAT Global 211.x.x.x(24844) Local 10.101.28.31(2205)
PAT Global 211.x.x.x(32524) Local 10.1.2.47(56471)
PAT Global 211.x.x.x(32012) Local 10.1.2.11(39603)
PAT Global 211.x.x.x(31500) Local 10.1.2.11(56975)
PAT Global 211.x.x.x(31500) Local 10.101.129.108(1825)
PAT Global 211.x.x.x(30988) Local 10.1.2.11(25106)
PAT Global 211.x.x.x(29964) Local 10.1.2.11(23049)
PAT Global 211.x.x.x(29452) Local 10.1.2.11(47968)
PAT Global 211.x.x.x(28940) Local 10.1.2.11(27356)
PAT Global 211.x.x.x(34572) Local 10.101.30.220(3354)
PAT Global 211.x.x.x(34060) Local 10.101.73.44(3060)
PAT Global 211.x.x.x(33036) Local 10.1.2.11(18828)
PAT Global 211.x.x.x(40716) Local 10.101.44.115(51250)
PAT Global 211.x.x.x(44812) Local 10.101.82.63(4954)
PAT Global 211.x.x.x(44300) Local 10.101.82.63(4048)
PAT Global 211.x.x.x(43788) Local 10.101.82.63(3721)
PAT Global 211.x.x.x(43276) Local 10.101.82.63(3358)
PAT Global 211.x.x.x(42764) Local 10.101.82.63(2962)
PAT Global 211.x.x.x(42252) Local 10.101.82.63(2622)
PAT Global 211.x.x.x(41740) Local 10.101.82.63(2304)
PAT Global 211.x.x.x(41228) Local 10.101.82.63(2141)
PAT Global 211.x.x.x(48908) Local 10.101.44.56(3840)
PAT Global 211.x.x.x(46348) Local 10.101.82.63(4559)
PAT Global 211.x.x.x(45836) Local 10.101.23.190(2602)
PAT Global 211.x.x.x(53004) Local 10.101.25.30(2504)
PAT Global 211.x.x.x(52492) Local 10.101.44.51(1218)
PAT Global 211.x.x.x(51980) Local 10.20.3.120(1142)
PAT Global 211.x.x.x(51468) Local 10.101.44.75(1102)
PAT Global 211.x.x.x(50956) Local 10.101.28.64(1402)
Problem with PAT is whenever you encounter websites that resricted activities based on IPs. e.g
rapidshare for downloading and etc. Then the users started complaining.
To solve this problem i believed we can simultaneously use NAT ( network address translation) and PAT (Port Address Translation) together. Currently working into it.
Keep you posted, soon