I have a new Drupal install and it works allright, everything loads fast, except for the Configuration page at admin/config. What I have done so far to try to tackle the problem: - Disabled all contrib modules, with no success. - Disabled the Update Manager module, no success either. - Enabled Devel and extended query logs, besides page execution time: ordinary pages take some 300 ms to load. The admin/config page is taking around 30000 ms to load. There is no evidence in the logs that it has to do with the database queries. On the Config page, none of them is above the threshold limit.
It then occurred to me trying something else: I am inside a corporate network and there are two different ways to enter this Drupal site: by checking the internal IP false address and by checking the external IP address the IT team has set for this server (open to the world).
I found that by navigating to the Configuration page from the internal IP address, there is no delay at all, the page loads fast! By navigating into it from the external IP address, the page gets these 30 seconds delays to load.
Any ideas on how I should try to fix this issue with the IT team? I have access to the server and I can run commands on the command line and maybe check server logs. I am not a Linux specialist, but I can follow instructions and run commands.