[dns-operations] TTL=0

m3047 m3047 at m3047.net
Thu Jan 17 23:15:15 UTC 2019

Who cares about the RFC? In practice, SOME caching resolvers (and that's 
being charitable) WILL answer with TTL=0. I've had to live with PFSense 
deployments which did this.

Which in turn leads to things like (for Mac users):

   dscacheutil -flushcache

Is that what you're talking about?

On Thu, 17 Jan 2019, Greg Choules wrote:
> [...]
> Is there ever a case, for cached answers, that the recursive server would
> answer the client with TTL=0? Or would that be illegal? RFC1034 states that
> records with TTL=0 "should not be cached". Note "should" and not "must".

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