Step 1. Login to your account at BigRock.
Step 2. Select "Manage Orders" (from top-navigation bar) and then click on "List/Search Orders". A list showing all your domains will be displayed.
Step 3. Click on the domain you wish to assign to your Tumblr blog.
Step 4. Move to the end of the page and find "DNS Management". Next click on "Manage DNS". We will now make changes in the DNS settings.
Step 5. Click on "CNAME Records" and then on "ADD CNAME RECORD"
Step 6. Adding the CNAME Record
For Value type in "domains.tumblr.com" (within the space provided for typing in a fully qualified domain name)
Specify a TTL value of 14400 seconds. TTL stands for Time To Live and defines time max required for the DNS settings to propagate across the net.
Click on 'Add Record' and you record would be saved.
Step 7. Next we have add 'A' NAME records. Click on "A Records" and click on "Add 'A' Record"
For Host Name leave 'blank' (i.e do not type in anything).
For Destination IPv4 Address enter the following I.P address
Click on "Add Record" to save.
Remember that a person wishing to access your blog might type in your domain (in their browser) in either of the following formats
We use a CNAME record (with the WWW prefix) to point http://www.yourdomain.com to your blog. An A-NAME record (without the WWW prefix) points http://yourdomain.com to your blog. Thus by creating both CNAME and A-NAME records for your tumblr blog, we are ensuring that the same will be accessible whether someone types WWW before your domain name or not
Step 8. Linking the domain to your Tumblr Blog.
A. Go to your Tumblr dashboard and click on the 'blog' you wish to add a custom domain to. Next Click on "Blog Settings"
B. Check the box that states "Use A Custom Domain Name" and enter your custom domain in the space below in the following format (i.e using a WWW prefix)
C. Scroll down and hit 'Save'
YOU ARE DONE NOW!
NOTE: It would take some time (upto 48 hours but usually lot less than that) for the domain settings to propagate across the internet.