SNAT Flow Confusion

SNAT is just one for of NAT. Just like what would happen on most home WiFi setups, 'cept its going the other way.

The F5 device in this case, keeps a table mapping the two sides of the connection together.

client source:port -> destination:port then f5 source:port -> pool member:port

This is a unique path, so established traffic can just follow that path back to the client.

Automap just allows the F5 to pick an appropriate source IP to use based on the route it has to the pool member. It can choose from any available Self IP on that outbound VLAN. With a snat pool, you can restrict which particular IP the F5 can choose (it doesn't have to be a Self IP, but can be).

Clear as mud?