After you add a CNAME record to your domain’s DNS settings, you can check the status of your change by looking up which CNAME records are currently in effect for your domain. Do this by either using a third-party web service or running DNS queries from your computer.

Check CNAME Using Free Web Service

  1. Open https://www.whatsmydns.net/ in a new browser tab.
  2. In the empty field, enter your cname (cdn.domain.com) and select CNAME from the dropdown menu.
  3. Click on Search.
  4. If the domain is propagated, a green checkmark will appear next to your CDN url (foo.bar.netdna-cdn.com) for all locations:

    CNAME check on whatsmydns.com

Note
If the CNAME has not propagated, a red X will appear next to certain (or all) locations.

Check CNAME Using Your Computer

The application nslookup comes with most operating systems and can be used to look up name server details from your Windows, Mac, or Linux command line.

To start the command line in Windows:

  1. Click Start > Run, enter “cmd” and press enter. (On Mac or Linux, start the terminal.)
  2. Enter the following command:
    nslookup -q=cname cdn.domain.com

This will return the following:

Server:	127.0.1.1
Address:	127.0.1.1#53
Non-authoritative answer:
cdn.domain.com	canonical name = foo.bar.netdna-cdn.com.
Note
Linux distributions without the dnsutils package don’t have nslookup and similar tools, but there’s a good replacement for each.

For a replacement to nslookup, use a tool called “drill” (a “dig” clone):

$ drill www.maxcdn.com
;; ->>HEADER<<- opcode: QUERY, rcode: NOERROR, id: 46722
;; flags: qr rd ra ; QUERY: 1, ANSWER: 2, AUTHORITY: 8, ADDITIONAL: 8
;; QUESTION SECTION:
;; www.maxcdn.com.    IN    A

;; ANSWER SECTION:
www.maxcdn.com.    121    IN    CNAME    maxfs.contentdeliverynetwork.netdna-cdn.com.
maxfs.contentdeliverynetwork.netdna-cdn.com.    193    IN    A    108.161.187.249

;; AUTHORITY SECTION:
netdna-cdn.com.    163539    IN    NS    dns4.p04.nsone.net.
netdna-cdn.com.    163539    IN    NS    dns2.p04.nsone.net.
netdna-cdn.com.    163539    IN    NS    ns-1716.awsdns-22.co.uk.
netdna-cdn.com.    163539    IN    NS    ns-946.awsdns-54.net.
netdna-cdn.com.    163539    IN    NS    ns-97.awsdns-12.com.
netdna-cdn.com.    163539    IN    NS    ns-1326.awsdns-37.org.
netdna-cdn.com.    163539    IN    NS    dns1.p04.nsone.net.
netdna-cdn.com.    163539    IN    NS    dns3.p04.nsone.net.

;; ADDITIONAL SECTION:
dns1.p04.nsone.net.    70799    IN    A    198.51.44.4
dns2.p04.nsone.net.    82098    IN    A    198.51.45.4
dns3.p04.nsone.net.    26250    IN    A    198.51.44.68
dns4.p04.nsone.net.    81340    IN    A    198.51.45.68
ns-97.awsdns-12.com.    137199    IN    A    205.251.192.97
ns-946.awsdns-54.net.    70496    IN    A    205.251.195.178
ns-1326.awsdns-37.org.    79487    IN    A    205.251.197.46
ns-1716.awsdns-22.co.uk.    70496    IN    A    205.251.198.180

;; Query time: 33 msec
;; SERVER: 89.216.1.50
;; WHEN: Mon Nov 30 16:01:07 2015
;; MSG SIZE  rcvd: 452

The relevant part of this output comes after the first two lines. Specifically, this tells us that cdn.domain.com is pointing to the canonical name foo.bar.netdna-cdn.com.

If you have any questions about troubleshooting the propagation of CNAMEs, please start a live chat or leave a comment below.

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