GoFuckYourself.com - Adult Webmaster Forum - View Single Post - Tech Geeks: Why does it take 2 days to switch when changing nameservers?

rowan · 09-10-2003, 04:01 PM

If you change a DNS record without 'preparing' then usually it will take at least 24 hours for 99% of the people to change over to the new IP. (some will continue accessing the old one MONTHS after you change it - you can't help them

)

Each DNS record has a time-to-live field, which defines the maximum length that it should be cached by an intermediate DNS cache (or end host such as a surfers computer). Most DNS setups seem to have a TTL between 24-48 hours usually. If you don't reduce this TTL field prior to changing the IP, then everywhere will cache it as per normal. The trick is to reduce the TTL to something small (like 120 seconds) at least a couple of days prior to changing the IP... so in theory, the old cached record with the old IP should only live a maximum of 2 minutes. You'll see surfers accessing the new server pretty much immediately.

If you are actually redelegating (changing the DNS servers that your domain points to) then that's an added delay, since the root servers do not update in real-time.

If you move from one host to another and you have both an IP and DNS server change then you're looking at 48+ hours for everything to propagate out properly. If the old host is able to point to the new IP then it should be a lot less painful.

09-10-2003, 04:01 PM
rowan Too lazy to set a custom title Join Date: Mar 2002 Location: Australia Posts: 17,393	If you change a DNS record without 'preparing' then usually it will take at least 24 hours for 99% of the people to change over to the new IP. (some will continue accessing the old one MONTHS after you change it - you can't help them ) Each DNS record has a time-to-live field, which defines the maximum length that it should be cached by an intermediate DNS cache (or end host such as a surfers computer). Most DNS setups seem to have a TTL between 24-48 hours usually. If you don't reduce this TTL field prior to changing the IP, then everywhere will cache it as per normal. The trick is to reduce the TTL to something small (like 120 seconds) at least a couple of days prior to changing the IP... so in theory, the old cached record with the old IP should only live a maximum of 2 minutes. You'll see surfers accessing the new server pretty much immediately. If you are actually redelegating (changing the DNS servers that your domain points to) then that's an added delay, since the root servers do not update in real-time. If you move from one host to another and you have both an IP and DNS server change then you're looking at 48+ hours for everything to propagate out properly. If the old host is able to point to the new IP then it should be a lot less painful.