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leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET
reply to HELLFIRE

Re: why does DNS take so long to work after login/off your VPN

said by HELLFIRE:

Either a routing issue or a DNS cache issue.

Shouldn't be routing issue since:
said by Packeteers:

i can ping any public IP directly within a few seconds of clearing my connection.

unless it is a selective issue only effecting some addresses.

DNS caching is much more likely, specifically the caching of negative results: a lookup fails during the connection change and the NXDOMAIN (non existent domain) response is cached. Subsequent search for the same domain returns cached response of NXDOMAIN despite the fact that the domain would resolve now.

Depending on the OS used the duration of this negative caching can be configured or disabled altogether. Alternatively there may be ways to flush the DNS cache.

Please note that it isn't just your computer that may have a DNS cache. Your home router may perform DNS caching as well.
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