DNS issue with pinging DNS servers - Help!

[maxrebo]

Hi,

I was wondering if anyone can help with this strange issue I have with 2 of our 3 DNS servers.

 

Setup

DNS 1 - Win 2k12 - 1 network card

DNS 2 - Win 2k8 - 2 network cards (Admin and Curric card)

DNS 3 - Win 2k8 - 2 network cards (Admin and Curric card)

 

I'm having (Intermittent) issues with pinging the 2 DNS servers by NetBIOS name from various PC`s

I will ping (NetBIOS name) either of the DNS servers (with 2 network cards) and it will reply only for an hour later (or less) to not reply and tries to resolve to the admin card.

An hour later it will reply to the curric card no problem.

 

The DNS servers configured on the workstation (auto ip settings) and DNS settings are to resolve to DNS 2 and DNS 3

 

In the DNS console (replicated between the 3 servers) are entries (static) for all DNS servers (including the admin card) - so its got a record in DNS?

 

When it wont resolve from NetBIOS name it will (always) resolve using the IP

 

I have looked in the Event view>Administrator events and also System and cant find anything (loss of connection etc..)

 

Any help would be very grateful!

[tmcd35]

You really, really, shouldn't have multi-homed DNS servers because, well you've just found out the reason. The problem is in the configuration of the 2 NICs. Why have they got two NICs? different subnets? How are the default gateways configured? What is likely to be happening is the computer is receiving the ping on one NIC and responding on the other, not the one the pinging PC is expecting the reply from.

[maxrebo]

You really, really, shouldn't have multi-homed DNS servers because, well you've just found out the reason. The problem is in the configuration of the 2 NICs. Why have they got two NICs? different subnets? How are the default gateways configured? What is likely to be happening is the computer is receiving the ping on one NIC and responding on the other, not the one the pinging PC is expecting the reply from.

 

Hi, thanks for the reply.

It was a setup I have inherited, we have both a Curriculum and admin domain, the servers are all on the Curriculum domain but have shares that the admin domain users want\need to access.

The cards on the servers are setup with the Curriculum gateway inputted on the curric card and only the IP + subnet and DNS settings inputted on the admin card (I have taken out the admin gateway entry)

[tmcd35]

Do the curriculum and admin domains use different IP ranges? Or are they both on the same subnet? Are the DNS server Domain Controllers or are your DC's separate? If they are separate are they running their own DNS or are these the only DNS servers?

 

If these are purely DNS servers and your DC's don't use them for anything at all then you may get away with Binding the DNS to specific NICs for each IP range: Configuring Multihomed Servers

[Stuclark]

You can multi-home DNS servers - you just need to ensure DNS is only active on one interface. (this is within the DNS server settings)

[maxrebo]

Do the curriculum and admin domains use different IP ranges? Or are they both on the same subnet? Are the DNS server Domain Controllers or are your DC's separate? If they are separate are they running their own DNS or are these the only DNS servers?

 

If these are purely DNS servers and your DC's don't use them for anything at all then you may get away with Binding the DNS to specific NICs for each IP range: Configuring Multihomed Servers

 

Yes both domains use different subnets

They are all DC`s as well as DNS servers

[maxrebo]

Im probably best setting within DNS manager to only listen on the Curric interface?

[tmcd35]

Yes both domains use different subnets

They are all DC`s as well as DNS servers

 

In that case, my advise would be contact some local high school and/or your local authority and see if you can get someone to come and look over it with you. I certainly wouldn't want to pick this apart in an internet forum.

 

The only other question I'd have is - are the two dual nic servers DC's on the same domain or is one admin and the other curriculum? It could be a simple as removing the admin nic from one server and the curriculum nic from the other, but I fear it's likely to be a bit messier if the two domains are sharing the same DNS servers.

[maxrebo]

In that case, my advise would be contact some local high school and/or your local authority and see if you can get someone to come and look over it with you. I certainly wouldn't want to pick this apart in an internet forum.

 

The only other question I'd have is - are the two dual nic servers DC's on the same domain or is one admin and the other curriculum? It could be a simple as removing the admin nic from one server and the curriculum nic from the other, but I fear it's likely to be a bit messier if the two domains are sharing the same DNS servers.

 

no, the admin domain has its own DC with dns installed etc.. and the DNS is managed by that server. Theres just an entry in the curric DNS for the admin server so they can access the shares on the curric.

The two dual nic servers are on the curric domain.

Im thinking I could just set the DNS to listen only on the curric card?

[tmcd35]

If I understand your network correctly, yes that should do it. Your admin machines use the admin DNS server on the admin DC. These servers are DC+DNS for curriculum only. I thought both networks were using the same DNS servers for a moment, thus the panic. If the admin cards are purely access to network shares and nothing else then yes, set DNS to respond only on the curric cards.

[tmcd35]

This thread and the MS links within are probably worth a read through as well: What are the risks of a multi-homed domain controller with Server 2008 R2? - Spiceworks

[maxrebo]

thanks for the advice and help - I have unchecked the Admin card from DNS manager - I will see how it goes today

 

Thanks