Hi all,

I have an account with two resellers, each one with my own personalised nameservers. For one I use ns1.domain.com
ns2.domain.com and for the other I use ns3.domain.com
ns4.domain.com

I would like to use each account as a back-up for critical sites on the other, with mirror sites being maintained for emergencies eg.....

A site on Reseller 1 would have nameservers of ...

ns1.domain.com
ns2.domain.com
ns3.domain.com
ns4.domain.com

A site on Reseller 2 would have nameservers of ...

ns3.domain.com
ns4.domain.com
ns1.domain.com
ns2.domain.com

My theory is that ns3 and ns4 will *only* kick in if Reseller 1 is down and vice-versa for Reseller 2.

1. Is this theory correct?

2. What happens to mail for a web site on Reseller 1 when the primary and secondary nameservers are unavailable? The web site (hopefully) will show under ns3/ns4 but where will the mail go?

Thanks

Chuck M.

You don't tell where your name servers are located. It probably works if ns1 and ns2 are located very close to reseller 1, and the same goes with ns3 & 4 with reseller 2. This assumes that if reseller 1 is down, then ns1 and ns2 are down.

But it might not work as you wanted it to be. Each DNS caches uses different algorithm in order to resolve a name. Some uses round robin, in which case both your accounts will be used. Some takes round trip time into account, in this case a visitor will be accessing one closest to his location, most of the time.

And there always DNS caching problem. You can eliminate this problem by using a lower TTL (like ten minutes).

About email, it is much easier, you can use MX record to assign priority to your servers. Mail servers will try to contact your highest priority server, and if it is not available, it will contact the second highest, and so on. Mail servers also can be configured to deliver mail to highest priority servers, if it find itself not the highest priority one.

Thanks for your reply. :)

You don't tell where your name servers are located. It probably works if ns1 and ns2 are located very close to reseller 1, and the same goes with ns3 & 4 with reseller 2. This assumes that if reseller 1 is down, then ns1 and ns2 are down.

The nameservers are with Opensrs - one reseller is in NE America, one in mid-America.

Some uses round robin, in which case both your accounts will be used.

Aaahh - I would not want this to happen...

Some takes round trip time into account, in this case a visitor will be accessing one closest to his location, most of the time.

...nor this. I only (if possible) want the alternate nameservers to become active if the primary and secondary are unavailable.

You can eliminate this problem by using a lower TTL (like ten minutes).

Could you please explain what this means?

About email, it is much easier, you can use MX record to assign priority to your servers.

OK - sounds good.

Chuck M.

If it is not acceptable to you, then you are out of luck unfortunately. That unless you have dedicated name servers that do monitoring to your web sites. Even with that, it will require some expensive customization with your DNS servers.

TTL number determines how long DNS caches around the world will cache your records. So if server #1 is down, the DNS record need to be changed to server #2, but if records for server #1 is already cached around the world, it will need time to expire on the caches.