Advantages of CGNAT
IP was originally designed according to the end-to-end principle for networking. This means that application protocols may expect to communicate directly between hosts without intermediate systems modifying the packet headers or payload. As NAT modifies the IP addresses at the very least and sometimes alters other protocol headers and payloads, NAT can break the communications. CGNAT solves this and other problems associated with using traditional NAT at scale with the inclusion of the following capabilities:
- Endpoint Independent Mapping (EIM), Endpoint Independent Filtering (EIF), and hairpinning provides transparent NAT connectivity. Traditional NAT implementations do not allow any traffic that is initiated from the outside (EIM, EIF) or for protocols that need to hairpin, i.e. loop their traffic back to the inside.
- Application-level gateway (ALG) was developed to solve the problem of NAT servers breaking communications. Based on proxy server technology, ALGs intelligently modify necessary application protocol headers and payloads to conform to the protocol being routed by the NAT.