what does 2 different DNS do?

will the secondary DNS act as backup?

[irock]

Hi, I've been running sites for couple years now, but I've never thought of this.

In Versign, I have to fill in 2-3 DNS server names. Since secondary DNS will take over the first one in the event of a failure, can I use the 2nd DNS to point to a backup server on another hosting company?

[glengara]

I've asked this in a couple of places with no reply; hope we get one here!

[Lisa]

DNS does use two or more name servers. Think of a name server as your local telephone operator. If one is busy, the other can answer the call and direct the call to you. You can do some neat stuff with DNS. If you are big enough you can have for example place a DNS server on every continent. So a person in China looking at your Chinese DNS server which will return your Chinese mirrored website to them... All with the same domain name. Not www2 stuff.

Cheap companies will offend place two name server on the same network. But the problem with that is they are backing each other up. So if one fails the other is likely to fail if for example the T1 which provides the connection for one fails. It is always nice to have nameservers on redundant networks or separate networks. Let’s say you reboot one name server.... Do you expect all your customer's websites to stop for that 60 seconds. Bottom line DNS needs to be near to 100% as possible.

[irock]

Lisa,

Thanks for the reply.

So, back to that 'China' example, I don't understand how the guy in China could be logged onto the Chinese-mirrored site.

Say, if I fill the following into Versign DNS...

ns1.rackshack.net
ns2.rackshack.net
ch1.chinese.net
ch2.chinese.net

I guess this isn't the point...

so, it's suffice to say that when the first 2 rackshack DNSes failed, the ch1 and ch2.chinese.net DNS will be up next...right?

[glengara]

I'm out of G this month due to a server problem, so I'm looking at this to solve any future outages.
I take it G wouldn't have any duplicate content problems with this?

[Lisa]

Well, let's say your DNS servers are...

ns1.<name>.net
ns2.<name>.net

When your customers try to resolve yourdomain.com they need to first resolve your name server which then resolves your domain name. So when your customers try to resolve ns1.<name>.net they will use their local name server. That local name server will try to figure out what IP address equals ns1.<name>.net. Well, the entry for ns1.<name>.net is a registered IP address. All name servers are required to register one IP address. IP addresses are divided and distributed by continent. So, 216.x.x.x is a North American only IP address. Well, if one IP resolves closer to you then your local name server would seek the answer from that closer address. So now the local name server is talking to yourdomain.com’s name server. Instead of returning one IP address it returns an array. So the array may look like this 12.34.56.78 (located in LA), 12.34.56.79 (located in LA), 56.78.89.01 (located in Hong Kong), 56.78.89.02 (located in Hong Kong), 127.128.129.130 (located in London), and 127.128.129.131 (located in London). The client being in China would use the Honk Kong IP address to reach your domain.