Doubt about ttl value

Kevin Darcy kcd at
Thu Mar 6 03:33:46 UTC 2008

Raghavendra wrote:
> Hi All,
>  I would like to know, ttl value sent by DNS server will be in minutes or seconds?
On the wire, the numeric value represents seconds. Various utilities, 
e.g. dig, may represent the same value in hours/days/weeks or other 
units of measure.
>  Is there any minimum and maximum value for ttl?
Minimum? 0
Maximum? It's a signed 32-bit number, so 2147483647 would be the limit, 
theoretically. Be aware, however, that many implementations, including 
BIND, limit the caching of records, regardless of what the TTL value is. 
For BIND, the default max-cache-ttl is 7 days.
>  because i am getting ttl value like 76, 140, 390..etc for different hostname.
Are you getting those from authoritative servers or from caching 
servers? If you're getting them from caching servers, it just means 
those records are approaching their expiration.

                           - Kevin

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