We operate a couple of web-servers and help manage other colleagues hosted various web-applications.

Where web-traffic significantly increases for a site, or periodically we re-host refreshing upon the latest hardware and operating system, we have to move a number of top-level domains.

Some of the sites we manage are global – (of course a web-site is global) – where the community is literally global we have to be aware of when we kick-off a Host Header IP change.

Where our predominant community is US-based an update at 08:00 UTC will hit the majority of our US community by their morning, between 4 and 8 hours later.

DNS Propagation time is one of those unknown factors in site-management; you just can’t say how long its going to take. We do use this batch file as a simple check, but this is only true from where its executed.

A World View of DNS Propagation

One useful tool we’ve spotted is whatsmydns.net which gives us a nice summary of DNS propagation around the world. This includes A, MX, CNAME where you’re migrating different parts of your identity.

Enter your sitename, select the record type (A for web) and click Search.

This is emrupdate.com part way through its DNS IP change, moving from 216.x to 76.

Its also handy to have a Skype, IM or ooVoo contacts around the globe to double-check & verify DNS migration.

You can’t beat a good Google mash-up to complete the picture. Clicking on a green (red) blob shows the IP details for your site at that location. A red blob would indicate no DNS value found.

Nick Harrington
team Ambay Software

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