To place a load balancer in a network effectively and utilize Layer 7 functionality, two things need to happen:

  • Traffic needs to flow through the load balancer on the way in
  • Return/response traffic needs to flow through the load balancer on the way out

To meet the requirements above there are two options; Layer 7 (L7) Transparency or L7 Non-Transparency. When a packet arrives at the LoadMaster, the source IP address of the packet is that of the client and the destination IP address is that of the Virtual Service. When L7 Transparency is enabled the packet is passed to the Real Server with the same source IP address of the packet but with the destination IP address changed to be the that of the Real Server.

With L7 Non-Transparency when the packet is being sent to the Real Server the LoadMaster will change the destination IP address of the packet to be the Real Server (as it does in L7 Transparent Mode) but it will also change the source IP address from the original client IP address to the IP address of the Virtual Service.

Document Purpose

This document serves as an explanation of network transparency, its implications and other related concepts.