DNS records change time

Kevin Darcy kcd at daimlerchrysler.com
Mon Feb 6 22:45:25 UTC 2006

Kevin Darcy wrote:

>Tester wrote:
>>Hi there,
>>If I will change some DNS records on my external DNS name server Bind 9, how
>>long it will take to propagate around the world, in other words when all
>>clients will be able to connect to these hosts whose IPs I changed from
>>outside? Thanks a lot, Calin
>Barring any connectivity issues, it could take as long as SOA.REFRESH 
>for a zone to propagate from a master to a slave. Once the change is on 
>all of the slaves, it is visible to caching resolvers [...]
Sorry, bad wording. I didn't mean to imply that the change needs to 
propagate to *all* slaves before it is visible to *any* caching 
resolvers. I was just stating the worst case here, that a given Internet 
client might be talking to a caching resolver which might get its data 
from the last slave to be updated with the change. So the maximum time 
would be SOA.REFRESH + TTL, and only if there's a single master/slave 
"hop" (for each additional such "hop", the worst-case propagation time 
goes up by another SOA.REFRESH seconds).

I also forgot to mention that NOTIFY optimizes the master/slave part of 
the propagation time, but it is *only* an optimization, and cannot be 
completely relied upon, so I wouldn't factor it into the worst-case numbers.

                                                            - Kevin

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