Difference between SNAT and DNAT

1. Source Network Address Translation (SNAT) :
SNAT, as name suggests, is a technique that translates source IP address generally when connecting from private IP address to public IP address. It maps source client IP address in a request to a translation defined on BIG-IP device. It is most common form of NAT that is used when internal host needs to initiate session to an external host or public host.

2. Destination Network Address Translation (DNAT) :
DNAT, as name suggests, is a technique that translates destination IP address generally when connecting from public IP address to private IP address. It is generally used to redirect packets destined for specific IP address or specific port on IP address, on one host simply to a different address mostly on different host.

Difference between SNAT and DNAT :

SNAT	DNAT
It is generally used to change private address or port into a public address or port for packets leaving network.	It is generally used to redirect incoming packets with destination of public address or port to private IP address or port inside network.
It translates source IP address within a connection to BIG-IP system IP address that one defines.	It translates IP addresses of internal servers that are protected by device to public IP addresses.
It is used to change source address of packet.	It is used to change destination address of packet.
It also changes source port in TCP/UDP headers.	It also changes destination port in TCP/UDP headers.
It generally allows multiple hosts on inside to get any host on outside.	It generally allows multiple hosts on outside to get single host on inside.
It is performed after routing decision is made.	It is performed before routing decision is made.
In this, destination IP address is maintained and source IP address is changed.	In this, source IP address is maintained and destination IP address is changed.
Client inside LAN and behind Firewall needs to browse Internet.	Website hosted inside data center behind Firewall and needs to be accessible to users over Internet