NAT types
Traditional NAT
Traditional NAT applies to the interface connected to the public network. It translates the source IP addresses of outgoing packets and destination IP addresses of incoming packets.
Bidirectional NAT
NAT translates the source and destination IP addresses of incoming packets on the receiving interface and outgoing packets on the sending interface.
Bidirectional NAT is applied when source and destination addresses overlap.
Twice NAT
Twice NAT translates the destination IP address on the receiving interface, and the source IP address on the sending interface. The receiving and sending interfaces are both NAT interfaces.
Twice NAT allows VPNs with overlapping addresses to access each other.
NAT hairpin
NAT hairpin allows internal hosts to access each other through NAT. The source and destination IP address of the packets are translated on the interface connected to the internal network.
NAT hairpin includes P2P and C/S modes:
P2P—Allows internal hosts to access each other through NAT.
C/S—Allows internal hosts to access internal servers through NAT.