SNAT Pool

A SNAT or SNAT pool is really irrespective of the server node's capabilities. TCP allows for 65,535 port numbers per IP address. Subtract the 1024 "well known" ports, and you have ~64k ports. The BIG-IP server side connection (in a full proxy configuration) is the client side connection to the server node. A stateful client will establish a connection to a server using a random source port, going to a known listening destination port (ie. port 80). If the client runs out of random ports to a given destination IP address, it can no longer make new connections to that destination address. The SNAT pool, therefore, allows the BIG-IP to spread the connections across multiple source addresses.

For example: you should think of 65535 concurrent connections as the maximum capacity for any given SNAT address. If you think more than 65535 connections may require translation, you should configure more SNAT addresses (for example, using a SNAT pool).

The SNAT address is able to process approximately 65535 concurrent connections for each pool member in the pool (each unique remote socket).

Please refer: https://support.f5.com/csp/article/k7820

hope this helps.