DNS puzzle

Jeff LaCoursiere jeff at jeff.net
Wed Aug 28 18:11:22 BST 2002

As I write this I am envisioning how I could setup a quick test case to
find the answer, but I am lazy at heart.  Imagine the following:

* Zone a.com with TTL of 5 days
* Zone b.com with TTL of 1 hour

* 'A' record in b.com called 'www' with a value
* 'CNAME' record in a.com called 'www' pointing to www.b.com

Now the issue:

A client asks his name server (not authoritative for either a.com or
b.com - lets say caching only) to resolve www.a.com and gets an answer.
Five minutes later the admin of b.com changes the address of the A
record.  Two hours later the client asks his name server again to resolve

What answer does he get?  The old value or the new value?



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