Port following is set when two services need to share persistence records. Typically, this is done for HTTP and HTTPS services so users maintain a server session, regardless of whether they connect securely or not.

If the Real Server for one of the Virtual Services fails, the persistence records for the same Real Server on the other Virtual Service will be cleared.

Port following has several requirements:

  • The Virtual Services must have the same set of Real Servers
  • The Virtual Service must be using the same persistence options

After meeting these conditions, in the Virtual Service modify screen there will be an option under Advanced Properties for Port Following. Ensure to set this on both Virtual Services to ensure that port following is done bi-directionally. Port following must be set up bi-directionally to ensure that, regardless of whether the client connects using HTTP or HTTPS, the persistence and session is saved.

Prior to LoadMaster firmware version 7.2.51, it was not possible to configure port following for Virtual Services where the Service Type was set to Generic. This is possible in version 7.2.51 and above.

Here is an example scenario where port following may be used:

  • When using “shopping cart” like services where a user selects items and adds them to a list, any persistence method can be used.
  • When the user decides to pay for the items, this is normally performed using a secure SSL (HTTPS) service.
  • When port following is turned on, the Real Server where the “shopping cart” connection is active will be selected for the SSL session.
  • This selection will only occur when a connection is still open from the same client (as determined by the source IP address), and if the SSL service has the same IP address as the “shopping cart” service.
  • For example, if a connection is made to the HTTP service of www.somewebsite.com, and then a new SSL connection is made to the same address, then the SSL session will be directed to the same Real Server as the original HTTP service.