DNS Change replication time

domain-namedomain-name-system

We have just changed our DNS record to point to a new server running IIS. How long will it take until the address is changed to the new server? Some people can still see the old server and some can see the new.

I have flushed the dns on my pc and it seems to be fine although it doesn't with another of my pcs.

Thanks

Best Answer

It depends entirely on the TTLs for the domain or individual resource record, and varies depending on when the record was fetched (and cached) by each distinct resolver throughout the Internet.

You can find out the TTL for your local resolver with dig:

$ dig serverfault.com a | grep serverfault | grep -v '\;'

serverfault.com. 44257 IN A 69.59.196.212

So for serverfault.com, my local resolver will hold onto this record for 44257 more seconds. To find the true TTL, we need to first identify the authoritative nameservers.

$ dig serverfault.com ns | grep NS | grep -v '\;'

serverfault.com. 86392 IN NS ns4.p19.dynect.net.

serverfault.com. 86392 IN NS ns1.p19.dynect.net.

serverfault.com. 86392 IN NS ns2.p19.dynect.net.

serverfault.com. 86392 IN NS ns3.p19.dynect.net.

Then we can query one of them directly for the TTL.

$ dig @204.13.250.19 serverfault.com | grep serverfault | grep -v '\;' | grep-v NS

serverfault.com. 86400 IN A 69.59.196.212

In this case, the resource record for "serverfault.com" is 86400 seconds (1 day).

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