Functions of 'Service Port' and 'Health Monitor'?

Service Port, when adding a pool member, defines the destination port the BIG-IP will attempt to connect to when creating a server-side connection.

Alias Service Port, which is a monitor setting, is used to configure the destination port of monitor connections.

Most often, the Alias Service Port is left at '*', which in natural language translates to 'use the port specified in the Service Port for the pool member'.

If however there is a dependency that needs to be recognized or a dashboard service that needs to be checked for availability, the Alias Service Port can be explicitly specified and the Service Port of the pool member will not be used when making monitor connections.