Need of primary and secondary DNS server.

[nsvora]

Hi All,
I am working on the proprietory Dynamic DNS client implementation . My DHCP and DDNS server are running on LINUX and would like to know some information about Secondary & Tertiary DNS Servers.
Currently, my client send the update to only Primary DNS server.

Could anyone kindly answer the following :
Why do we need secondary and tertiary servers?
My understanding regarding them is that :
- Any client sends the update only to the Primary DNS server.
- Primary server updates the records to secondary and tertiary.
- Any DNS Queries can be answered by any of the primary, secondary or tertiary servers.

What happens when the primary server is not reachable?
Should client send the update record to secondary DNS Server in that case?

Note:
I have proprietory implementation of DHCP and DDNS client so i dont want to have DHCP server updating the DNS server.

Thanks in advance,

With Regards,
nsvora

[Compunuts]

Why do we need secondary and tertiary servers?

You answered yourself.

What happens when the primary server is not reachable?

Should client send the update record to secondary DNS Server in that case?

Nope, unless if you want them to. Then, you will have to reverse-update your primary server. Basically what you do is have the primary server running and the rest is all caching naming servers. Ideally, the secondary and tertiary should be located in different subnet from primary as well as geographical region (although I know it's hard to do, like I said "ideally".).

[nsvora]

You answered yourself.



Nope, unless if you want them to. Then, you will have to reverse-update your primary server. Basically what you do is have the primary server running and the rest is all caching naming servers. Ideally, the secondary and tertiary should be located in different subnet from primary as well as geographical region (although I know it's hard to do, like I said "ideally".).

Thanks for the reply compunuts.
From the minimal knowledge that I have, i understand that:
1) We need secondary and Tertiary Servers for redundancy purpose. So in case primary server is not available, client query could be answered by secondary or tertiary servers.
But this is true only for the DNS queries. Updates should be sent to only primary server.
2) In case primary server is not reachable , secondary server should be configured as primary server. And updates should be sent only to current primary server.
(Only one server can be authoritative for a zone. Could this be another reason for having single update point? )

In any case, the dns "updates" should be sent only to the primary server.
Secondary & Tertiary servers are configured only for redundancy of "queries". We cannot have redundancy for updates.

Could you kindly correct me if I am wrong.

With Regards,
nsvora

[Compunuts]

Could you kindly correct me if I am wrong.

You got that absolutely right.

[Compunuts]

2) In case primary server is not reachable , secondary server should be configured as primary server. And updates should be sent only to current primary server.

I re-read it and wants to make a little clarification.

You DO NOT need to configure secondary server as primary server in anycase. Almost all client boxes can be configured with more than one DNS server entries so the configuration is already there. If your primary goes down, the client will automatically ask secondary server for answers. MOST DNS servers on the net are non-authorative meaning they only store DNS entries for information only (with no updating).

If you want your primary to be there all the time, you will need to look at some other ways to do it such as redundancy or hardware failover solutions.

[nsvora]

I re-read it and wants to make a little clarification.

You DO NOT need to configure secondary server as primary server in anycase. Almost all client boxes can be configured with more than one DNS server entries so the configuration is already there. If your primary goes down, the client will automatically ask secondary server for answers. MOST DNS servers on the net are non-authorative meaning they only store DNS entries for information only (with no updating).

If you want your primary to be there all the time, you will need to look at some other ways to do it such as redundancy or hardware failover solutions.

Thanks for the reply compunuts.
I had ment configuring the secondary server as primary server for updates.
Because I think the client would and should always send the updates to the primary server even if the secondary/ tertiary servers are configured on the client.
So basically what i meant was secondary and tertiary servers which are configured on the client will be used for redundancy of queries only and not for updates. Am I right ?

[Compunuts]

Yeap.

[nsvora]

Yeap.

Thanks a lot for the clarification Compunuts !