Many applications use the Akamai Content Delivery Network (CDN) to accelerate global delivery of the application to clients. The request to the Virtual IP address will come from the Akamai CDN, not the original client. Due to the way that Akamai connects, normal persistence methods will not work.
To have proper persistence (also known as stickiness or affinity) for traffic using the Akamai CDN, set the Persistence Mode to Selected Header and set the Header field name to True-Client-IP. This can be done on the Virtual Service modify screen in the LoadMaster Web User Interface (WUI) - Virtual Services > View/Modify Services > Modify > Standard Options.