Multiple A records in DNS
 

Hi,

Is it possible to have multiple A records for a domain pointing to two different IP's from two different ISP's so as to avoid downtime if one of the ISP fails, similar to the lines what google has. I tried to test it internally but it does not seem to work.

What I did was this.

prasanta -> 192.168.4.117
prasanta -> 192.168.4.121

Both of the above are `A` records, but when 192.168.4.117 IP goes down, I am not able to ping `prasanta` with 192.168.4.121.

Please let me know, if some thing else needs to be done.

Regards,

--
Prasanta

Hi,

What you're doing now is called round robin
What you want to do is called high availability

Hi Bathory,

Thanks for the above. Will it be possible to do it for IP's from two different ISP's, with two different IP address class? As for a live example,

assamonnet.org -> 158.144.1.20
assamonnet.org -> 123.108.33.12

What I have noticed it that request are not moving to the other IP when the first one is unreachable and vice versa.

Regards,

--
Prasanta

Yes this is possible. As I told you it's called round robin and it's used to share the traffic of a busy site between different servers.
What you want to do, is to implement a failover system, so when a server goes down the traffic is redirected to the other server. This is done with specific software and/or hardware.

Hi,
Yes, using heartbeat one can do it. But I would not like to use this application for this.

------------
| Web Server |
------------
|
---------------------------------
| |
------------ ------------
| Firewall | | Firewall |
------------ ------------
| |
| |
ISP 1 ISP 2


Can this be also be done in the above mentioned scenario?

Regards,

--
Prasanta

Without a failover solution, if one server goes down, then with your scenario every 2nd request will fail. This is because of the way round robin works:
The 1st request goes to the 1st server, the 2nd request to the 2nd and in your case the 3rd will go again to the 1st server.
You can use ping to test this as follows::
Run ping assamonnet.org. The 1st time it will ping 158.144.1.20. Stop and rerun ping assamonnet.org and you'll see it will use 123.108.33.12

That is true, every second request fails. In the above scenario is there a possibility of putting the fail over, since it is one server which serves the request.

Regards,

--
Prasanta

You could try this to see if it fits your needs

Regards