TTLs on A records?

online-reg online-reg at enigmedia.com
Thu Apr 30 22:29:01 UTC 2009


Hi All:  I'm running Bind 9.5.0-P1 / Fedora on my primary NS.

Are TTLs on individual A records universally supported?

I have a domain with a TTL of "3h", and I wanted to route traffic between 
two servers in that domain quickly, so I set the TTL to the A record like:

www    300    A    123.123.123.123
;www    300    A    123.123.123.124

so I could uncomment one and comment the other to manually switch between 
them.

I've had that setup for several weeks during testing...and I just reversed 
the records, incremented the serial, and reloaded BIND.

On my secondary NS (Bind 9.5.0-P1 / Freebsd 7), when I dig the "www" record, 
I see the TTL counting down from 300 (Cool!), and after it reaches "0", the 
IP address resets to the new one....perfect!

On my Windows DC (server2008), the change was also picked up after 5 
minutes.

When I use some other lookup services, however (like samspade.org), the old 
IP address shows up for much longer...like it's caching it and ignoring the 
TTL for the record. Should I expect that behavior?

TIA 




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