Seamless way to change IP on website ??

You might do this late night if you're concerned about downtime.
Domain names need propagate to the server, IP's can be changed without downtime as they are the server so to speak.

 

Provided there is an available IP address to switch to, it is possible to simply use the feature in WHM to change an account IP address. I agree with Infopro that this type of change would be best performed during a time of low usage where the server is the least busy, typically this may be during late night hours.

Here are the two menu paths in WHM where the change can be performed:
WHM: Main >> Account Functions >> Change Site's IP Address
WHM: Main >> IP Functions >> Change Site's IP Address

Here is our documentation for the above:
AcctFunctions < AllDocumentation/WHMDocs < TWiki
IPFunctions < AllDocumentation/WHMDocs < TWiki
ChangeSiteIP < AllDocumentation/WHMDocs < TWiki


The only propagation required would be for recent site visitors that also have a cached copy of the DNS query result from a time before the IP change within the minimum TTL period (time frame) defined in the DNS zone. Visitors will see the IP change immediately if they do not have a current cached entry of the domain, or after their cached DNS query result expires.

It is possible for affected visitors to attempt forcing their DNS cache to be flushed (cleared or reset), but this process or method to flush the DNS cache varies depending on the OS being used on their own computer (e.g., Windows, Mac OS X).

For Windows, via a Command Prompt window:

Code:

ipconfig /flushdns

For Mac OS X, via a Terminal window:

Code:

dscacheutil -flushcache

For any OS, it may also be necessary to close and re-open the browser windows (because the browsers could also cache DNS queries), and preferably close all browser windows before flushing the DNS cache.