DNS Problems

[KI114]

We have recently switched to a new server, changing the IP on the domain. However, some of our clients are still being sent to our old server. We changed the IP on the 18th of April, why are some users still using old server?

 

Thanks

[gizmola]

Two ways.  DNS has a value called the TTL (Time to live) that is associated with a domain.  This tells server that they should cache the DNS entry for that domain once they read it.  Big ISP's may be even more aggressive and just ignore the TTL altogether and cache it for a week.  Often the default TTL for many domains quite long.

 

Secondly the workstations themselves depending on the operating system will cache DNS for domains they've visited, and they may never pick up the right DNS information without a reboot.

 

Keep in mind that if for example, someone used a DNS server that let's say had cached information for your domain from the 17, with a long TTL, any clients which go through that DNS server will not be getting the new information.  If this is a website, it's always good to put in a redirect on the server to the new server to catch people who have the old information until such time as everything is sorted out.

[KI114]

How could I put a redirect on the old server though? Because surely it'd just be back to the domain, which then again would point to the old server. So, they'd end up in a loop.

[Philip]

You could always link to the new server's IP

[gizmola]

Yes, you need to use an IP address or an entirely different domain.