Resolving weirdness

[taproot]

Hi,

I moved a site between two cpanel server both of which are mine. The servers are ns1 and ns2. I moved the site from ns1 to ns2 2 days ago at which point the DNS had not been set to my servers yet. Last night the customer updated their DNS and pointed it to my servers. Some people are seeing the site on ns1 and some on ns2. I re-sync'd the nameservers and did a DNS cleanup. I checked the entries on both server manually in /var/named/domain.org.db and they both are set to the correct IP address. Any idea why some people would still see the site resolving to ns1 at this point?

Cheers,
TR

[Spiral]

When you update a DNS record, notification of the change is sent up to the
root servers for the TLD of your domain name and then that update feeds
back down to all the servers around the world based on TTL.

The problem is that many ISP's implement localized DNS caching within
their own networks and pull live DNS updates on their own schedules
instead of TTL settings. In plain English, this means that the DNS
information may be updated and correct but some ISPs may have old
cached data pointing back to the old information that sticks around for
a few days longer until their servers decide to update the information.

To complicate matters further, most PCs also cache DNS routing information
locally as well and if you frequently visit a site and that site changes it's
IP address, your computer may still try to go to the old IP address even
though anyone new visiting the same site would correctly go to the
new address. This can of course be changed by flushing your local DNS
cache or by adding a route to the new IP in the host file on the computer
of the visitor who is visiting that site:

ipconfig /flushdns     (Windows XP/Vista command to flush DNS cache)

When transferring sites to a new server, I often duplicate the site on the
new server and setup a mirroring update to keep the old site in sync and
then go ahead and update the DNS information on the OLD server
to point to the NEW IP address on the NEW server so that
connections start going over to the new server and those who have old
improper cache data can still see the site on the OLD server.
After a few days, I go ahead and update the DNS servers themselves
for the domain and then cut the OLD site.

By doing it this way, there is no appearance of downtime and everything
is seamlessly transferred from the original server to the new server.

If you want to be sure you are connecting to a specific server, you can
put the domain and www address in your local hosts file:

C:\Windows\System32\Drivers\Etc\Hosts    (Windows XP/Vista)

/etc/hosts    (Linux / Unix)

Anyway, taproot, to answer the question in your post directly, the issue
you are experiencing is common and is natural and is caused by the
update transitional period where some ISPs have live DNS data and others
have old cached data and has more to do with how the worldwide DNS
system works and isn't anything to do with your server or what you did!

Everything will sort itself on it's own in a couple of days!

[taproot]

Hi,

Thanks for the input. I did not explain very well though as the DNS was never ever set to the ns1 ip address so it was not a propagation issue. It seems however that restarting bind solved the problem. Basically when cpanel updated the DNS records for some reason Bind on NS1 was still serving the old IP address as I had originally created the new account there and then moved it before DNS was moved to my servers. Even though the db file in /var/named/ was correct, it did not respond with the right answer until restart I guess bind has some caching locally or was just not reading the updated file for some reason. Bleh.

Thanks!

[Spiral]

If the new server wasn't originally the authoritative server, that could be the issue and would yes make it cache old DNS information just like everyone else.

[diyamput]

could you show me on your /var/log/messages ?
maybe i have same problem