For quite some time my Safari wouldn’t connect to my internet gateway, which is a Fritz!Box 7590, running with the IP 172.20.20.254. No chance to get to the admin interface, even though it was no problem at all from other systems. I didn’t put any effort into it since I could always connect from my iPad. Strange enough, the Mac OS Safari wouldn’t even show an error, but only say it couldn’t connect as if the target was not available at all.
But today I thought better of it – and found a way to make it work. Ok, how did I get there? I first installed Mozilla Firefox, and this browser had no problem connecting to the internet gateway – it only showed a warning that this site uses a self-signed certificate which is not trusted. So I downloaded the certificate in the Firefox browser (clicking the lock sign and downloading the PEM formatted certificate). Then I started keychain access on my Mac and did the drag and drop of the PEM cert into the keychain. Just make sure that you have selected Keychains = System and Category = Certificates. Thus the Cert started to appear in keychain, I double-clicked it and changed the trust to „trust all“. Authorized the changes and then started up Safari again.
What happened? Safari now had no issue to reach the Fritz!Box admin page! Great, success!