F5 LTM is quiate a complicated product with regard to how it can effect the traffic as it passes through.
This is a simple explanation of how the Source IP address of a request may change based on the chosen configuration options for a Virtual server or NAT destination.
The Source IP may change or remain the same. The change may be becuse of either:
- SNAT List entry
- SNAT Pool entry
- NAT entry
Also bear in mind that if there is a Virtual Server and NAT destination object that both reference the same IP and port the Virtual Server is preferred – but the NAT setting may still take place if no specific configuration in the Virtual server config.