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Comment see Time-To-Live (TTL) for a DNS record?

ayi

I would like to see the Time-To-Live (TTL) value for a CNAME record.
I have access to <a href="http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man1/dig.1.html" rel="noopener nofollow ugc">dig</a> (on Apple Mac OS X), which gives me an answer like this:
<pre><code class="lang-auto">% dig host.example.gov
<SNIP>
;; ANSWER SECTION:
host.example.gov. 43200 IN CNAME host1.example.gov.
host1.example.gov. 43200 IN A 192.168.16.10

</code></pre>
Is the value ‘43200’ the TTL for this DNS record?
<hr>
Source : <a href="http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man1/dig.1.html" rel="noopener nofollow ugc">Server Fault</a>

ayi_2

Yes, the number there is the number of seconds left until that record expires (providing we’re not querying the authoritative nameserver). Obviously with a CNAME there’s a level of redirection, so the TTL for the A record it points to in this case may be important as well.
If you wait a couple of seconds and run dig again on your local nameserver, you should see that TTL number decrease by the number of seconds you waited (approximately). When it hits 0, it’ll refresh or if your nameserver refreshes the zone for some reason.
As mentioned above, there is a difference between dig being run against a nameserver with a cached entry and the nameserver that is authoritative for that entry.
(in the examples I use below I use the <code>+noauthority</code> <code>+noquestion</code> & <code>+nostats</code> flags just to keep the output terse).
Note the difference between the following queries:
<pre><code class="lang-auto">$ dig +noauthority +noquestion +nostats stackoverflow.com @ns2.p19.dynect.net.

; <<>> DiG 9.7.0-P1 <<>> +noauthority +noquestion +nostats stackoverflow.com @ns2.p19.dynect.net.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50066
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; ANSWER SECTION:
stackoverflow.com. 432000 IN A 69.59.196.211

</code></pre>
So in the above query, we’re querying a nameserver that is authoritative for <a href="http://stackoverflow.com">stackoverflow.com</a>. If you notice the <code>flags</code> section, pay special attention to the aa flag which denotes this is an authoritative answer (i.e. not cached).
<pre><code class="lang-auto">$ dig +noauthority +noquestion +noadditional +nostats stackoverflow.com

; <<>> DiG 9.7.0-P1 <<>> +noauthority +noquestion +noadditional +nostats stackoverflow.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43514
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4

;; ANSWER SECTION:
stackoverflow.com. 246696 IN A 69.59.196.211

</code></pre>
In the above query, we don’t have an aa flag, and the TTL will keep decreasing as we query and query. This is essentially the counter I was talking about previously.