Firefox invalidate dns cache
browser-cache, dns, firefox
Solution
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.
Problem
I was too quick about visiting a site I set up on a customer server, and Firefox now remembers, that the default site for (example) ``` testsite.mycompanyname.com (non existing subdomain, same as *.mycompanyname.com) ``` is ``` www.mycompanyname.dk - or rather the IP of the default server ``` I have then later set up the public DNS (a-record) to redirect to another server, but Firefox remembers the default IP adress. Chrome/IE/Safari - no problem, as they have not visited that site before DNS kicked in... I have set these in about:config: ``` network.dns.disablePrefetch = true network.dnsCacheExpiration = 0 ``` Anything else? I really need firebug to debug the frontend on that site.... Cheers