Is it possible and to enable Host > Host Settings > Is Web Farm? in DNN 5.3.1 CE or is PE required?

I tried editing the web.config and adding a record to the dbo.WebServers Table, however with no success.

That's great to hear.

Do you happen to have info on how multiple servers are detected?

As mentioned, I added a record in the dbo.Webservers Table (now displaying 3 servers, the first record is my local desktop, on which I created the site, second record is Webserver1, third record is Webserver2).

Enable Is Webfarm? still is unchecked in Host Settings.

I noticed the "Enabled" column was set to "False" on all three records in the dbo.Webservers Table, so I tried altering these to "True", again no success however.

(btw. excuse me for misspelling your name in another post)

Yes I have checked out the document, however I think it's not up to date anymore since 5.1 / introduction of Professional Edition. I found an blogpost that stated that iswebfarm detection was altered in 5.1.4 (nr. of servers in the dbo.Webservers table) and will be altered again in 5.2. It doesn't say in what way it will be altered in 5.2. Both IIS webservers are in the dbo.Webservers table (I copied the record of webserver1, pasted it and changed the name to webserver2).