WARNING: All of your nameservers (listed at the parent nameservers) are in the same Class C (technically, /24) address space, which means that they are probably at the same physical location. Your nameservers should be at geographically dispersed locations. You should not have all of your nameservers at the same location. RFC2182 3.1 goes into more detail about secondary nameserver location.
Does it mean I have to obtain some other IPs based in other countries or continent to setup as my nameservers?
like NS3 & NS4?
Basically It means you should have your namservers on different networks.
This is to add redundancy and prevent problems such as:
I have 4 namservers on 2 boxes.
They all are on 1 T1 Line.
My T1 is down because of a lighting strike.
Now all my nameservers are down and no one can visit my site.
Then again if you are running a small shop where all of your server (mail, web, etc.) are on the same network, adding off site name servers won't really do much when your network goes down.
You should have secondary mail servers, DNS servers, Web servers on a seperate back up connection such as a DSL line with a static IP.
Basically you know you fullfilled the requirements of RFC2182 3.1 if they are on different subnets, with independent internet connections.
126.96.36.199 for nameserver 1 using verizon DSL
188.8.131.52 for nameserver 2 using GTE T1
Hope this makes sense.
PS: Each country to a limited extent have a number of IP addresses. the first 2 octects... such as 4.41. .... in an IP address block determine the country of orgin. There are exceptions such as the US which has several different IP blocks. This is because the "internet" was developed in part by the DOD decades ago.