For testing you can set the server to use external_url as the IP for the server. For example, I’m currently doing my server now I could set it to:
and in my web browser I could then use that to connect without using DNS. If you have a DNS server, then you need to add a A record with the IP of your server, and the hostname you are wanting to use - gitlab.testmed.com or whatever it should be.
For mine right now I am configuring the host as gitlab.local and I add this to /etc/hosts on the server, as well as to my local /etc/hosts on my laptop so that I can test with this as well as the external_url value.
If on Windows, then edit c:\windows\system32\drivers\etc\hosts, and add in here the IP address of your server, and the hostname - that way you can use your system without DNS, but use the hostname, so:
In the Windows hosts or /etc/hosts on Linux, then you don’t need DNS but it’s only useful for debugging. Ideally you want to configure DNS.