Firefox invalidate dns cache

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

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.

I've been using the "Clear Recent History\cache" solution for a while now, but I've noticed that it stopped working after one of firefox updates (probably 20.0.1). Because of that I've switched to <https://addons.mozilla.org/en-US/firefox/addon/dns-cache/> add-on to do the DNS clearing. I hope this will help someone with the same problem.

Edit: Changed the url as suggested by Haozhun.

Edit2: Unfortunately as of FireFox 32, this plugin is no longer compatible and cannot be used. Possibly https://addons.mozilla.org/en-US/firefox/addon/dns-flusher/ might be able to replace it.

Install the addon DNS Flusher, which works for me.

I found that network.dnsCacheExpiration = 0 alone did not quite do the trick, but if you also set network.dnsCacheEntries = 0 then the DNS cache gets disabled for good. So:

network.dnsCacheEntries = 0
network.dnsCacheExpiration = 0

The following methods, which worked at some point, do not work presently (doing all of them doesn't work):

• Restarting the browser
• Clearing the browser cache
• Setting network.dnsCacheExpiration=0
• ipconfig /flushdns

However, you can open a new private window, private windows evidently don't use the same DNS cache as the regular windows (which is comforting).