F5 LTM – HOW EGRESS SOURCE IP CAN VARY FROM INGRESS SOURCE IP – VS & NAT destinations

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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:

  • Automap
  • 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.

The following shows how Source IP varies once traffic passes through the F5 LTM after hitting a Virtual Server Destination

SNAT-impact-on-VS

SNAT-impact-notes

The following shows how Source IP varies once traffic passes through the F5 LTM after hitting a NAT Destination

SNAT-impact-on-NAT