An external class is independent from internal classes - they are two different kind of objects. An internal class is a dataset that's content is included directly in the bigip.conf file. External classes are stored completely in a single external file with the bigip.conf only containing a reference to it. I'll try to answer your questions one by one.
"I switched from writing internal string classes in default file /config/bigip.conf to writing to an external file using external classes.
But then the string classes I write are dependent of the external class. Is it always the case ?"
Not quite sure what you mean by string classes being dependent. If you have an internal string class and an external string class, the two are different objects and independent of eachother. But, if you create an external class, then the configuration for that (with the location of the file on disk) is dependent on the actual content in the external class file.
"I mean if I want to write to an external file, is each external file specific to a class ??"
Yes, each external class object points to it's own external class file on disk.
"Can I write and group several classes within a same external file ?"
No. There is a one-to-one relationship between an external file configuration and it's storage location on disk.
Hope this helps...
Nimbostratus
