dns and multiple TTLs, why do that?
 

Hello,

My question is about DNS use of the $TTL directive. I realize the $TTL directive stands for TimeToLive, my question is why would you specify different TTLs in the zone file? I have a zone file with

$TTL 300
machine
machine
machine
TTL 3600
machine
machine
machine
TTL 300
machine
machine
machine

I'm not sure why you just wouldn't specify the same TTL for all systems or at least not have all the 300's grouped together and all 3600s grouped together. The file I'm looking at has about 12 different groups of 300 and 3600 TTLs.

Hi,

You can give a smaller TTL to host(s) that change frequently and you don't want them to be cached for a long time.
Now regarding why the hosts are not grouped together according to their TTL, you should ask the person that created the zone file

Regards

Thank you. I am familiar with how DNS works and how to set it up, but never really looked into the logic of having different TTLs. I've always just set a TTL at the top and left it at that. My guess is that the previous admin was trying to group the systems in some other way and applied different TTL values to the groups. I've always just put them in address order.