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Is it possible to check how much time is left before a nameserver like 8.8.8.8 will update its records from my nameserver?

Greatestswordsman
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  • The OpenDNS [CacheCheck](http://www.opendns.com/support/cache/) tool lets you force an update before TTL. – Nic Feb 24 '12 at 05:17

2 Answers2

11

Using dig you can check the TTL of a record - like so:

; <<>> DiG 9.7.3 <<>> @8.8.8.8 www.serverfault.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 3937
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.serverfault.com.       IN  A

;; ANSWER SECTION:
www.serverfault.com.    1800    IN  CNAME   serverfault.com.
serverfault.com.    1800    IN  A   64.34.119.12

;; Query time: 88 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Thu Feb 23 23:15:23 2012
;; MSG SIZE  rcvd: 67

Specifically, you'll want to pay attention to the values in the answer (1800 in this case)

;; ANSWER SECTION:
www.serverfault.com.    1800    IN  CNAME   serverfault.com.
serverfault.com.    1800    IN  A   64.34.119.12

1800 is the number of seconds until the TTL expires and the record is refreshed on the nameserver (8.8.8.8).

If you run the command a few times, you'll see the TTL number go down, so as of the time of writing this, the TTL is now like so (1659 sec)

;; ANSWER SECTION:
www.serverfault.com.    1659    IN  CNAME   serverfault.com.
serverfault.com.    1659    IN  A   64.34.119.12
thinice
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    @Greatestswordsman Keep in mind that the server you're querying isn't necessarily at the same place in its TTL timer as **every** server behind 8.8.8.8; there are many anycasted nodes, and which you query depends on your location. One timer running down doesn't mean it'll immediately refresh everywhere; you need to wait for your record's full TTL time. – Shane Madden Feb 24 '12 at 05:22
  • A good place to see a general geographical sitrep of DNS updates is to use a site such as 'whereisitup.com' (I have no relation) – thinice Feb 24 '12 at 06:23
  • This can be abbreviated to `dig +noall +answer serverfault.com.` – tripleee Aug 07 '19 at 10:21
5

For Windows (natively) you can use nslookup.

C:\>nslookup -debug www.serverfault.com 8.8.8.8

Got answer:
     HEADER:
         opcode = QUERY, id = 4, rcode = NOERROR
         header flags:  response, want recursion, recursion avail.
         questions = 1,  answers = 2,  authority records = 0,  additional = 0
    QUESTIONS:
        www.serverfault.com, type = A, class = IN
    ANSWERS:
    ->  www.serverfault.com
        canonical name = serverfault.com
        ttl = 1791 (29 mins 51 secs)**
    ->  serverfault.com
        internet address = 64.34.119.12
        ttl = 1791 (29 mins 51 secs)**
Dave
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