When you have to change the nameserver to move web host or modify the server’s IP address, the most important consideration is DNS Propagation. DNS changes spread from DNS server to DNS server after DNS change.

Because of the huge volume of requests generated by a system like DNS, the DNS resolution process allows for caching (ie. the local recording and subsequent consultation of the results of a DNS query) for a given period of time after a successful answer. DNS Propagation makes DNS is able to read or resolve hostname or domain name into your new IP address, rather than the old IP address.

How long a resolver caches a DNS response (ie. how long a DNS response remains valid) is determined by a value called the time to live (TTL). The TTL is set by the administrator of the DNS server handing out the response. The period of validity may vary from just seconds to days or even weeks.

In this post, I will introduct 5 online tools for DNS Propagation. These tools are usefull if you have recently setup a new domain, or have changed nameservers of an existing domain.

ViewDNS.Info

ViewDNS.Info has one of the best and easiest to use DNS Propagation checker. You just go to the website, provide the domain name for which you want to check DNS Propagation status. Then this DNS Propagation checker will look up the propagation status in 19 servers, and will report status for each of them. It shows the IP result from the servers from which it got result, and shows a cross for the servers for which it did get any result. This is very inuititive.

What’s My DNS

Another great free DNS Propagation checker is at What’s my DNS. It is an online service that allows you to instantly perform a DNS lookup to check a hostnames current IP Address and other DNS information against a selection of random name servers around the world. This is especially useful to check the current state of DNS propagation after making changes to your domains zones.

Preshweb.co.uk

Preshweb.co.uk has another free DNS Propagation checker. It uses much lesser number of servers, and is a bit slow, but it provides lot of information. For all the servers that send a positive response about propagation, it shows CNAME, as well as “A” record for the website. This helps to see that propagation is happening uniformly over the servers.

DNS Check

This is another simple DNS Propagation checker. It shows results from just 4-5 servers, but it shows all the A records and MX records from those servers.

Mob.Net DNS Lookup

Mob.net has another free tool to check DNS propagation status. It does support lot of servers. However, I have put this at end of the list as I did not like the interface a lot, and it took quite some time to report the results. However, it shows Time to Live (TTL) info for each server, and this is the only DNS propagation checker in this list that does that.