Checking DNS Propagation

DNS “Propagation”

The word “propagation” is poorly-chosen, as it makes it sound as though DNS changes always take time to take effect across the whole internet. In fact, so long as no-one has cached the old value for a DNS record, the new one will take effect immediately. Those that have requested the data before the change will have to wait until the TTL expires before their local caching nameserver will request fresh data from one of the domain’s nameservers. These notes show how you can check how many seconds of TTL remain for the data in a caching nameserver, giving an indication of when people using that nameserver will see the changed data.

To minimise the time taken for everyone to see a change to DNS records, reduce the TTL in advance of the change to a low value, perhaps 60 seconds. Once this change to the TTL has had time to be fed to all the caching nameservers, you know that changes to that DNS record will be seen by everyone within 60 seconds of the change being made. Once the change is working OK, set the TTL back to an hour, perhaps more, to reduce the load on your domain’s nameservers.

On Windows

Use nslookup from the command line:

C:\> nslookup
> set debug
> domain-to-check.com

look for the TTL value, which says how many seconds before the data gets

refreshed from the DNS servers for the domain. This is what your local DNS
server is doing. You can try other servers to see whether they have
different times left on the domain data:

> server ns1.sprintlink.net
> domain-to-check.com

You can use any public DNS server, and your ISP’s ones. If you don’t have direct control over your own primary and secondary DNS machines, don’t forget to check the zone data using them too!

On Linux

# dig domain-to-check.com

look for the TTL value, the second value in the ANSWER section. Try
different DNS servers like this:

# dig domain-to-check.com @ns1.sprintlink.net

You can use any public DNS server, and your ISP’s ones. If you don’t have direct control over your own primary and secondary DNS machines, don’t forget to check the zone data using them too!

Public DNS Servers

Here are some public DNS servers that you can use to check how other parts of the internet are seeing your DNS data:

resolver.qwest.net
vnsc-lc-dsl.genuity.net
ns-1.iastate.edu
dns1.mci.com
ns1.us.prserv.net

ns2.mindspring.com
dns1.rcsntx.sbcglobal.net
ns2.us.dellhost.com
ns3.earthlink.net
ns.east.isi.edu
ns1.super-dns.com
ns1.sprintlink.net
cache01.ns.uu.net
ns1.mcleodusa.net

ns2.iinet.net.au
ns1.fcable.co.kr
dns1.cableplus.com.cn
ns1.interplanet.com.mx