サーバーが見つかりませんでした | Firefox ヘルプ
Change proxy setting, in about:preferences Network Settings. I tried the options "no proxy", "Auto-detect proxy" and "Use system proxy" (the latter was the default). In about:config I set the "network.dns.disableIPv6" to TRUE; In about:config I set the "network.dns.disablePrefetch" to TRUE; The issue seems firefox-specific. Tuning Firefox Quantum This is a lot of processing for almost no gain especially if you have a good local DNS cache on your computer: network.dns.disablePrefetch;true ; Firefox will call home to keep track of how often you use it. If you don't like that then set: network.captive-portal-service.enabled;false Ubuntu vm under proxy: browser is not able to resolve dns
705610 - setting network.dns.disablePrefetch to true
Aug 11, 2015 How To Increase Firefox Page Loading Speed - GreenGeeks Change network.dns.disablePrefetch to True. Next, change network.prefetch-next to False. Finally, change the value of network.http.speculative-parallel-limit to 0. Toggle Hardware Acceleration and WebGL. These functions use your graphics card to speed up certain functions, especially loading videos.
I've found for Firefox that quitting and restarting works. The relevant settings in about:config are network.dnsCacheEntries and network.dnsCacheExpiration, which can be set to 0 in order to disable caching. Caching by local system is typically 1 hour. Diagnostic: ping, like other applications, uses local system DNS cache
In rare cases, the DNS server might have an advanced security or firewall configuration. If the server is located on another network that is reachable only through an intermediate host (such as a packet filtering router or proxy server), the DNS server might use a non-standard port …