Firefox invalidate dns cache [closed]

DNS caching occurs at multiple levels:
Application asks local system,
which asks locally configured resolving DNS server,
which asks authoritative DNS servers.

Caching by Application varies.

• 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
• Flush MacOsX 10.8: sudo killall -HUP mDNSResponder (reference)
  (May vary for other versions)
• Flush Windows: ipconfig /flushdns (only if the DNS caching service, HKLM\SYSTEM\CurrentControlSet\Services\Dnscache, is enabled; check with net start|findstr /i dns or compmgmt.msc)
• Linux/Unix may use nscd (name services caching daemon), or dnsmasq, or both …

Caching by local resolving DNS server may run to several days, depending on TTL associated with DNS record.

• Diagnostic: nslookup first reports address of resolving server, then address requested.
• Flush BIND: rndc flush or rndc flushname DOMAIN.NAME

TTL stands for “time to live” a term used to describe how long a DNS record is to be deemed valid by the requesting client or server. A short TTL means that the requester is told not to cache a DNS lookup for too long. The TTL can range from mere seconds (e.g. for DynDNS and similar) to days or weeks.