Time to live (TTL) is a mechanism that limits the lifetime of dns records in the Domain Name System (DNS).
| Tutorial details | |
|---|---|
| Difficulty | Easy (rss) |
| Root privileges | No |
| Requirements | dig or host |
| Time | N/A |
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dig command syntax to find ttl
The dig command syntax is:
dig type name dig @ns-name-server-here type name dig [optipns] @ns-name-server-here type name dig [options] type name
Examples
In this example, find out ttl for www.cyberciti.biz a record:
dig a www.cyberciti.bizSample outputs:
dig a www.cyberciti.biz
; <<>> DiG 9.7.3 <<>> a www.cyberciti.biz
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34721
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4
;; QUESTION SECTION:
;www.cyberciti.biz. IN A
;; ANSWER SECTION:
www.cyberciti.biz. 30 IN A 75.126.153.206
;; AUTHORITY SECTION:
cyberciti.biz. 161081 IN NS ns-1075.awsdns-06.org.
cyberciti.biz. 161081 IN NS ns-866.awsdns-44.net.
cyberciti.biz. 161081 IN NS ns-243.awsdns-30.com.
cyberciti.biz. 161081 IN NS ns-1947.awsdns-51.co.uk.
;; ADDITIONAL SECTION:
ns-243.awsdns-30.com. 161081 IN A 205.251.192.243
ns-866.awsdns-44.net. 161081 IN A 205.251.195.98
ns-1075.awsdns-06.org. 161081 IN A 205.251.196.51
ns-1947.awsdns-51.co.uk. 161081 IN A 205.251.199.155
;; Query time: 201 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sat May 4 16:18:18 2013
;; MSG SIZE rcvd: 255
For www.cyberciti.biz ttl is set to 30 seconds. To just find out ttl, use the following syntax:
dig +nocmd +noall +answer +ttlid type name-here dig +nocmd +noall +answer +ttlid a www.cyberciti.biz
Sample outputs:
www.cyberciti.biz. 30 IN A 75.126.153.206
A few more examples:
## Find ttl for IPv6 record ## dig +nocmd +noall +answer +ttlid aaaa www.cyberciti.biz www.cyberciti.biz. 592804 IN AAAA 2607:f0d0:1002:51::4 ## Find ttl for mx record ## dig +nocmd +noall +answer +ttlid mx www.cyberciti.biz cyberciti.biz. 3555 IN MX 5 alt2.aspmx.l.google.com. cyberciti.biz. 3555 IN MX 10 aspmx2.googlemail.com. cyberciti.biz. 3555 IN MX 10 aspmx3.googlemail.com. cyberciti.biz. 3555 IN MX 1 aspmx.l.google.com. cyberciti.biz. 3555 IN MX 5 alt1.aspmx.l.google.com.
Where,
- +nocmd – Toggles the printing of the initial comment in the output identifying the version of dig and the query options that have been applied. This comment is printed by default.
- +noall – Set or clear all display flags.
- +answer – Display [do not display] the answer section of a reply. The default is to display it.
- +ttlid – Display [do not display] the TTL when printing the record.
A note about query directly to authoritative name server for ttl
You can skip caching recursive name server and get fresh ttl value using the following syntax:
dig +trace a www.cyberciti.biz dig +trace +nocmd +noall +answer +ttlid aaaa www.cyberciti.biz
Sample outputs:
Fig.01: Displaying the ttl value for an IPV6 of www.cyberciti.biz
host command syntax to find ttl
The host command syntax is:
host -a -t type name
Examples
To see ttl for an IPv6 record for www.cyberciti.biz, enter:
$ host -a -t aaaa www.cyberciti.biz
Sample outputs:
Trying "www.cyberciti.biz" ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57539 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4 ;; QUESTION SECTION: ;www.cyberciti.biz. IN AAAA ;; ANSWER SECTION: www.cyberciti.biz. 592445 IN AAAA 2607:f0d0:1002:51::4 ;; AUTHORITY SECTION: cyberciti.biz. 160433 IN NS ns-243.awsdns-30.com. cyberciti.biz. 160433 IN NS ns-1075.awsdns-06.org. cyberciti.biz. 160433 IN NS ns-1947.awsdns-51.co.uk. cyberciti.biz. 160433 IN NS ns-866.awsdns-44.net. ;; ADDITIONAL SECTION: ns-243.awsdns-30.com. 160433 IN A 205.251.192.243 ns-866.awsdns-44.net. 160433 IN A 205.251.195.98 ns-1075.awsdns-06.org. 160433 IN A 205.251.196.51 ns-1947.awsdns-51.co.uk. 160433 IN A 205.251.199.155 Received 267 bytes from 127.0.0.1#53 in 0 ms
The ttl for www.cyberciti.biz is set to 592445. A few more examples:
## Show an IPv4 a record ## host -a -t a www.cyberciti.biz ## Show max record ## host -a -t mx cyberciti.biz ## Show cname record host -a -t cname s0.cyberciti.org host -a -t cname s13.cyberciti.org
See also
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Hi,
Fine topic, good to know.
Typo here:
“find out ttl for http://www.cyberciti.biz a recored:”
recored => record
— Philippe
The faq has been updated. I appreciate your post.
what is “id” refers to ??
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57539