Here is a web site with a quick and easy way to check how changes to your DNS settings have propagated around the Internet:
There is no such activity "propagation" in DNS.
Just to clarify for those that aren't DNS experts <G>:
"DNS propagation" is a term commonly used to describe problems where DNS data is changed, but not accessed immediately by DNS servers that have old values that are cached. This is a bad term to use, because it implies that when you make a change, the change is not made immediately, but instead slowly goes out to other servers. This is not the case.
What happens is that at the precise moment you make a DNS change, there is a good chance that other DNS servers on the Internet recently retrieved the record you are changing, and if so, they have the old value cached. Until the TTL expires, they will use the old data. This is by design.
The URL that was given out previously, and the "ISP cached DNS lookup" tool at http://www.DNSstuff.com , give you a "snapshot" of what information DNS servers have about a DNS record. This is useful before making a change, so you have an idea of what to expect after making the change. It is also useful after making a change, to see how long it will be before major DNS servers have the new data.
When making a change, the problem of cached records can be minimized by reducing the TTL ahead of time. For example, if the TTL is currently 86400 seconds (1 day), you can reduce it to 3600 seconds (1 hour). Then, 24 hours from now you can reduce it even further if you want (say to 300 seconds, or 5 minutes). Then an hour later, you can make the DNS change, and change the TTL back to 86400 seconds. Then, there will only be a 5-minute period where the record will be in limbo, with two different values out there.
One major warning, though: If you have made a mistake and set the TTL very high (several weeks/months/years), you're stuck. There is no way for new records to get out to DNS servers that have those very high values cached. Therefore, you MUST be careful never to use a TTL that is way too high.
-Scott
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