Source address affinity persistence, also known as simple persistence, tracks sessions based only on the source IP address. When a client requests a connection to a virtual server that supports source address affinity persistence, Local Traffic Manager checks to see if that client previously connected, and if so, returns the client to the same pool member.
The persistence mask feature works only for virtual servers that implement source address affinity persistence. By adding a persistence mask, you identify a range of source IP addresses to manage together as a single source address affinity persistent connection when connecting to the pool.
Source address affinity persistence profile
Specifies the duration, in seconds, of a persistence entry. For background information on setting timeout values, see Chapter 1, Introducing BIG-IP Local Traffic Manager.