Is it possible to automatically point server A to server B if in case server A goes down? If so what is this called and what do I need to do to achieve this?


  • Are they both in the same network? – Christopher Perrin Dec 8 '12 at 22:56
  • Server B should be on a different network . I am ask this because our site has been down for 6 hours now and my client is asking if this kind of setup is possible. – r2b2 Dec 8 '12 at 22:59
  • Not via DNS. You'd need to reroute the IP to the other server. – Christopher Perrin Dec 8 '12 at 23:00
  • And how do I do that? If i have a different IP on my secondary DNS wouldn't that work? – r2b2 Dec 8 '12 at 23:15
  • Two different IPs in DNS will make the DNS Server switch through all the IPs regardless wether the host is behind it is online or not. – Christopher Perrin Dec 8 '12 at 23:25

To keep the host online you'd need to migrate the IP to a host that is still available. A hot spare. This is easiest if they are in the same network.

If your server is linux based you can use IPAT

The only solution I could think of that involves DNS, would be to set up a very very low TTL (like 1 minute) and then change the A record if a server goes down.

  • The web hosting support i talk to points me to Private name servers. Im not quite sure if this will do it – r2b2 Dec 8 '12 at 23:36
  • However, setting a very low TTL is against RFC 1912. It's OK to prepare temporarily for upcoming changes to stabilize fast and then going back to higher TTLs. – Theuni Dec 8 '12 at 23:42

That is known as high availability, it can be done by number of way ... first you need to determine what those servers are and what they will serve. You need to look to solutions starting from something simple like round-robin DNS to clustering up to high availability with DRBD or network protocols protocols like HSRP,VRRP and GlBP

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