Hi all,

All my domains are registered with powerpipe(reseller of enom).

If I change anything in the enom DNS record, like web server IP address, I found it will effective in a very short period of time. Let say 5 or 10 mins.

If I want to do DNS load balancing, I can have 2 servers, one minor another. If one server bandwidth reach the limit, I can just change the web server IP at encom and it will effective 5 or 10 mins later. So why I still need to run Round Robin DNS? Am I correct?

Even though you can change the record in your DNS, many ISPs will have your old IP cached for some time. The length of time varies.

But my ISP change the route to the new IP address after I changed the DNS record for 5 mins to 10 mins. I do a lot of traceroute around the world and the result is the same. So I just don't know what method enom use to make the changes so fast.

I think you're missing something here.

When you make a change with eNom, you are correct in your conclusion that eNom rapidly updates all of their DNS servers. You are also seemingly correct that your ISP has a very short cache timeout and therefore allows you to see changes rapidly.

What you aren't seeing is the effect this change has on one of your petential clients whose ISP may have as much as a 24 hour cache timeout for DNS entries. Just because you see the change rapidly, doesn't mean that everyone sees the change rapidly.

This delay is typically referred to a propagation time. To be safe you should allow 48 hours or propagation time when you change a DNS entry if you don't want to exclude anyone from your site.