We have a primary, secondary and tertiary servers, all located in different regions. All three machines run Windows Server 2008 R2. The secondary and tertiary servers provide backup for the primary server.
Every week, we do a test fail-over from the primary to the secondary, and the primary to the tertiary. This test has no issues when testing the secondary, but has a networking problem on the tertiary.
I log into the primary server to access the site on our tertiary server. The site's DNS is resolved using easyDNS which we update to point to the tertiary server, then wait the allotted time for the records to update.
This process works fine, but my question is that why does it behave differently if I change the hosts file of the primary server to point to the tertiary, versus if I do it in easyDNS.
In other words:
Scenario A: Using Primary server Edit hosts file -> points to Tertiary Server Access site from primary server, while being hosted tertiary server, no issues. Scenario B: Using Primary server Log into easyDNS, update the dns A record Access site from primary server, while being hosted tertiary server, site has networking / other accessibility issues.
What is the difference in the DNS look ups between scenarios A and B?