Re: Multiple DNS servers load balancing

[William Stacey [MVP]]

The client resolvers are supposed to balance this for you. Eventually all
dns server ip in the client list will be tried and the RTT (round trip time)
will be updated. The lowest RTT will be used. That helps if dns servers on
different subnet (ie local/remote) If they are all on same network then I
don't know a good way. You could manually order them differently on the
clients or via dhcp scopes (however scope solution will not work if all on
same scope.)

--
William Stacey, MVP

"pankaj" <pan...@discussions.microsoft.com> wrote in message
news:809312E4-5D2B-4D70...@microsoft.com...
> Hi, i have a primary DNS server & 2 Secondary servers for my domain. Is
there a way to achieve some kind of load balancing among the three DNS
servers. How is the load distribution achieved so that not one server gets
overloaded responding to dns queries?
>
> PS: I am not talking about Round-Robin.
>
> Thanks.

[pankaj]

Thank you for the reply. I guess i am now confused. Does it mean all Primary
& Secondary DNS servers configured in the client will be tried & the server
with the
least RTT will be selected? Till now my thinking was the Client's primary
server will be the first to respond & only if the primary fails the secondary
will reply. Could you please clarify my confusion. Thanks again.

[William Stacey [MVP]]

The list is just that - a list. It try the first one until it fails to
reply or until the RRT algo dertermines it is time for the next one to have
shot so they both can have real RRTs and the best one wins until it fails to
reply or it is time to try the next one again. I don't remember the exact
detail on the logic, but it is in Technet or msdn somewhere. I would not
worry too much about it. How many users are hitting it? Cheers!

--
William Stacey, MVP

"pankaj" <pan...@discussions.microsoft.com> wrote in message

news:F42557B2-41E3-4F08...@microsoft.com...

[Jonathan de Boyne Pollard]

p> Hi, i have a primary DNS server & 2 Secondary servers for my domain.
p> Is there a way to achieve some kind of load balancing among the three
p> DNS servers.

Yes. Do nothing. Resolving proxy DNS servers will spread the load
(some resolving proxy DNS server softwares more than others).

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/dns-database-replication.html>

p> PS: I am not talking about Round-Robin.

Good.

[pankaj]

Thank you for the reply. It makes more sense now :-) . I added another dns
server(secondary) for my internet domain. I have added this new server's
address with the provider where my domain is registered. I see the root
servers now have NS record for this new DNS server. However the new server is
unable to respond to dns query. Firewall has been opened for this new server.
There aren't any errors in the event log of the server. Whatelse should i
check? Thanks again for your help.

[William Stacey [MVP]]

Now I am confused. Your OP talking about spreading Query load to multiple
DNS servers AFAICT. If that is the case, then the DNS servers have nothing
to do with what IP the client resolver picks to send a query to. Did I miss
your intention?

--
William Stacey, MVP

"pankaj" <pan...@discussions.microsoft.com> wrote in message

news:1909D826-A0EA-4FFA...@microsoft.com...

[pankaj]

sorry.. no this was my second question which i added to the same post.

[Jonathan de Boyne Pollard]

p> However the new server is unable to respond to dns query. Firewall
p> has been opened for this new server. There aren't any errors in
p> the event log of the server.

* Check IP connectivity.
* Check UDP/IP connectivity.
* Send a DNS query from the same machine.
* Send a DNS query from another machine.