Persistence Primary Cookie and fallback source address persistence

Cookie persistence puts the burden of session affinity on the client by sending a cookie that is encoded with the load balancing information for that user session (pool, node, port). Other persistence mechanisms, including source, create an in-memory session table entry on the BIG-IP and map some piece of unique client information (ie. the source IP) to the load balancing information. When you have both of these applied, the primary will always be used until it disappears, as in if the client stops sending the cookie.