The “None” option means that no SNAT is applied. This means that the real client IP is sent to the servers, which can be useful if you need your servers to see the real client IP for logging or other purposes.
Transparency: The back-end servers can see the real client IPs.
Routing Complications: The back-end servers need to have proper routing in place to return the traffic to the client through the load balancer. This can add a layer of complexity to the network configuration.
Auto Map is a simple method for performing SNAT. It automatically uses the self IP (the IP address of the outgoing interface) for translation.
Simplicity: It’s easy to configure and use.
Dynamic: If the IP of the self (egress) interface changes, the SNAT address will change accordingly.
Limited Control: You can’t specify a particular IP or a range of IPs for SNAT. It will always use the IP of the self (outbound) interface.
The SNAT option allows you to specify a single address or a pool of addresses for source NAT.
Control: Allows you to define a specific IP or a range of IPs for all SNAT.
Scalability: Using a pool of IP addresses can provide better scalability for larger networks or those with higher levels of traffic.
Complexity: SNAT is more complex to configure compared to Auto Map.
Management: Requires more network administration to manage and monitor the pool of IP addresses.
Recommendations and Best Practices:
“None” should be used sparingly, as it might cause asymmetric routing. Use it only when your servers need to see the client’s actual IP, and you have correct return routing in place.
“Auto Map” is the easiest option to implement and is generally recommended for most standard applications. It’s best when you don’t need to use a specific range of source IPs.
The “SNAT” option provides the most control over your source IPs and is best when you have specific requirements for your outbound IPs.
Keep in mind that the best practice for your environment may vary depending on your network architecture, size, traffic patterns, and specific business requirements.