NAT is a method that converts a local IP address of a system into a global and unique IP address before the transmission of information takes place over the external network (the Internet). NAT as a technology is used as a firewall. Multiple IP addresses are used internally by an organization to combine multiple Integrated Services Digital Network (ISDN) connections (Internet connections that are established with an ISDN modem card via phone line) into a single Internet connection. A system on NAT cannot be accessed by external network systems. NAT increases network security by hiding the internal structure of a network from the system outside the network. The drawbacks of NAT are as follows:
- Incoming connections are blocked
- Troubleshooting in NAT is complex, because the IP address changes
NAT is of two types- Static NAT (SNAT) and Dynamic NAT (DNAT).