Multihomed DC's

We have a test lab with 2 DC's (1 AD Server/1Member server). Member Server.
W2K3, with dual NICs that responds to domain traffic Vlan, 192.160.1.0/27 and
Internet Vlan, 192.168.1.32/27. Internet traffic is outbound only for
purposes of updating WSUS, AV pattern updates. The server is protected by
Cisco CBAC Firewall.

How can I force all update traffic (http) to use the 192.168.1.32 vlan? Is
their a better way I can design network flow, with the priority on server
protection.

Thanks in advance for help

 

What have you set as the default gateway for this machine? If it is using
a router with a 192.168.1.x IP address as its default gateway, most traffic
will use the 192.168.1.32 interface. The only traffic using the 192.160.1.x
interface will be traffic going to machines on the 192.160.1.0/27 VLAN.

 

In

Along with Bill's suggestions, it is really not recommended to mutlihome a
DC. It is hugely problematic due to the multiple interefaces and DNS
registration.

However, if you insist, here is a step by step to alter default DC behavior
to make it work for you:
================================
(USe this one):
********************************
Multihomed DCs, DNS, RRAS servers.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
Below are the manual steps in more detail, which I had outlined in the above
paragraph:

Honestly, multi-homed DCs are not recommended because of the associated
issues that can occur, as you've encountered. We usually recommend
purchasing an inexpensive Linksys, DLink, etc, Cable/DSL router to perform
NAT for you, take out the extra NIC off the DC, but still let the DC handle
DHCP (and not the router).

Little background on AD and DNS:
First, just to get this out of the way, if you have your ISP's DNS addresses
in your IP configuration (DCs and clients), they need to be REMOVED.

If the ISP's DNS is in there, this will cause additional problems.

Also, AD registers certain records in DNS in the form of SRV records that
signify AD's resource and service locations. When there are multiple NICs,
each NIC registers. IF a client, or another DC queries DNS for this DC, it
may get the wrong record. One factor controlling this is Round Robin. If a
DC or client on another subnet that the DC is not configured on queries for
it, Round Robin will kick in offering one or the other. If the wrong one
gets offered, it may not have a route to it. On the other hand, Subnetmask
Priortization will ensure a querying client will get an IP that corresponds
to the subnet it's on, which will work. To insure everything works, stick
with one NIC.

Since this DC is multi-homed, it requires additional configuration to
prevent the public interface addresses from being registered in DNS. This
creates a problem for internal clients locating AD to authenticate and find
other services and resources such as the Global Catalog, file sharing and
the SYSVOL DFS share and can cause GPO errors with Userenv 1000 events to be
logged, authenticating to shares and printers, logging on takes forever,
among numerous other issues.

But if you like, there are some registry changes to eliminate the
registration of the external NIC. Here's the whole list of manual steps to
follow.

But believe me, it's much easier to just get a separate NAT device or
multihome a non-DC then having to alter the DC. - Good luck!

1. Insure that all the NICS only point to your internal DNS server(s) only
and none others, such as your ISP's DNS servers' IP addresses.

2. In Network & Dialup properties, Advanced Menu item, Advanced Settings,
move the internal NIC (the network that AD is on) to the top of the binding
order (top of the list).

3. Disable the ability for the outer NIC to register. The procedure, as
mentioned, involves identifying the outer NIC's GUID number. This link will
show you how:
246804 - How to Enable-Disable Windows 2000 Dynamic DNS Registrations (per
NIC too):
http://support.microsoft.com/?id=246804

4. Disable NetBIOS on the outside NIC. That is performed by choosing to
disable NetBIOS in IP Properties, Advanced, and you will find that under the
"WINS" tab. You may want to look at step #3 in the article to show you how
to disable NetBIOS on the RRAS interfaces if this is a RRAS server.
296379 - How to Disable NetBIOS on an Incoming Remote Access Interface
[Registry Entry]:
http://support.microsoft.com/?id=296379

Note: A standard Windows service, called the "Browser service", provides the
list of machines, workgroup and domain names that you see in "My Network
Places" (or the legacy term "Network Neighborhood"). The Browser service
relies on the NetBIOS service. One major requirement of NetBIOS service is a
machine can only have one name to one IP address. It's sort of a
fingerprint. You can't have two brothers named Darrell. A multihomed machine
will cause duplicate name errors on itself because Windows sees itself with
the same name in the Browse List (My Network Places), but with different
IPs. You can only have one, hence the error generated.

5. Disable the "File and Print Service" and disable the "MS Client Service"
on the outer NIC. That is done in NIC properties by unchecking the
respective service under the general properties page. If you need these
services on the outside NIC (which is unlikely), which allow other machines
to connect to your machine for accessing resource on your machine (shared
folders, printers, etc.), then you will probably need to keep them enabled.

6. Uncheck "Register this connection" under IP properties, Advanced
settings, "DNS" tab.

7. Delete the outer NIC IP address, disable Netlogon registration, and
manually create the required records

a. In DNS under the zone name, (your DNS domain name), delete the outer NIC's
IP references for the "LdapIpAddress". If this is a GC, you will need to
delete the GC IP record as well (the "GcIpAddress"). To do that, in the DNS
console, under the zone name, you will see the _msdcs folder. Under that,
you will see the _gc folder. To the right, you will see the IP address
referencing the GC address. That is called the GcIpAddress. Delete the IP
addresses referencing the outer NIC.

i. To stop these two records from registering that information, use the
steps provided in the links below:
Private Network Interfaces on a Domain Controller Are Registered in
DNShttp://support.microsoft.com/?id=295328

ii. The one section of the article that disables these records is done with
this registry entry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters
(Create this Multi-String Value under it):
Registry value: DnsAvoidRegisterRecords
Data type: REG_MULTI_SZ
Values: LdapIpAddress
GcIpAddress

iii. Here is more information on these and other Netlogon Service records:
Restrict the DNS SRV resource records updated by the Netlogon service
[including GC]:
http://www.microsoft.com/technet/tr...proddocs/standard/sag_dns_pro_no_rr_in_ad.asp

b. Then you will need to manually create these two records in DNS with the
IP addresses that you need for the DC. To create the LdapIpAddress, create a
new host under the domain, but leave the "hostname" field blank, and provide
the internal IP of the DC, which results in a record that looks like:
(same as parent) A 192.168.5.200 (192.168.5.200 is used for illustrative
purposes)

i. You need to also manually create the GcIpAddress as well, if this is a
GC. That would be under the _msdcs._gc SRV record under the zone. It is
created in the same fashion as the LdapIpAddress mentioned above.

8. In the DNS console, right click the server name, choose properties, then
under the "Interfaces" tab, force it only to listen to the internal NIC's IP
address, and not the IP address of the outer NIC.

9. Since this is also a DNS server, the IPs from all NICs will register,
even if you tell it not to in the NIC properties. See this to show you how
to stop that behavior (this procedure is for Windows 2000, but will also
work for Windows 2003):

275554 - The Host's A Record Is Registered in DNS After You Choose Not to
Register the Connection's Address:
http://support.microsoft.com/?id=275554

10. If you haven't done so, configure a forwarder. You can use 4.2.2.2 if
not sure which DNS to forward to until you've got the DNS address of your
ISP. How to set a forwarder?
Depending on your operating system,choose one of the following articles:

300202 - HOW TO: Configure DNS for Internet Access in Windows 2000
http://support.microsoft.com/?id=300202&FR=1

323380 - HOW TO: Configure DNS for Internet Access in Windows Server 2003
(How to configure a forwarder):
http://support.microsoft.com/d/id?=323380

Active Directory communication fails on multihomed domain controllers
http://support.microsoft.com/kb/272294


<==*** Some additional reading ***==>
More links to read up and understand what is going on:

292822 - Name Resolution and Connectivity Issues on Windows 2000 Domain
Controller with Routing and Remote Access and DNS Insta {DNS and RRAS and
unwanted IPs registering]:
http://support.microsoft.com/?id=292822

Active Directory communication fails on multihomed domain controllers
http://support.microsoft.com/kb/272294

246804 - How to enable or disable DNS updates in Windows 2000 and in Windows
Server 2003
http://support.microsoft.com/?id=246804

295328 - Private Network Interfaces on a Domain Controller Are Registered in
DNS
[also shows DnsAvoidRegisterRecords LdapIpAddress to avoid reg sameasparent
private IP]:
http://support.microsoft.com/?id=295328

306602 - How to Optimize the Location of a DC or GC That Resides Outside of
a Client's
Site [Includes info LdapIpAddress and GcIpAddress information and the SRV
mnemonic values]:
http://support.microsoft.com/?id=306602

825036 - Best practices for DNS client settings in Windows 2000 Server and
in Windows Server 2003 (including how-to configure a forwarder):
http://support.microsoft.com/default.aspx?scid=kb;en-us;825036

291382 - Frequently asked questions about Windows 2000 DNS and Windows
Server 2003 DNS
http://support.microsoft.com/default.aspx?scid=kb;en-us;291382

296379 - How to Disable NetBIOS on an Incoming Remote Access Interface
[Registry Entry]:
http://support.microsoft.com/?id=296379


Rid Pool Errors and other mutlhomed DC errors, and how to configure a
multihomed DC, Ace Fekay, 24 Feb 2006
http://www.ureader.com/message/3244572.aspx

_________________________
+++++++++++++++++++++++++++++++++++++++++++++++++++++++


--
Ace
Innovative IT Concepts, Inc (IITCI)
Willow Grove, PA

This posting is provided "AS-IS" with no warranties or guarantees and
confers no rights.

Ace Fekay, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSE+I, MCT, MVP
Microsoft MVP - Directory Services
Microsoft Certified Trainer

Having difficulty reading or finding responses to your post?
Instead of the website you're using, I suggest to use OEx (Outlook Express
or any other newsreader), and configure a news account, pointing to
news.microsoft.com. This is a direct link to the Microsoft Public
Newsgroups. It is FREE and requires NO ISP's Usenet account. OEx allows you
to easily find, track threads, cross-post, sort by date, poster's name,
watched threads or subject.
It's easy:

How to Configure OEx for Internet News
http://support.microsoft.com/?id=171164

Infinite Diversities in Infinite Combinations
Assimilation Imminent. Resistance is Futile
"Very funny Scotty. Now, beam down my clothes."

The only constant in life is change...

 

Hi Ace,

I aggree with that! The original post is a bit confusing. I read it to
mean that the multihomed server is the member server.

 

In

I agree, I wasn't sure either. So I gave him my standard riot act about
multihomed DCs! If they are multihomed DCs, it is probably what he DID NOT
want to herar.



Ace

 

Hello Ace,

I also have a multihomed DC (and TS, shame on me, I know) with Win 2000
Server and everything worked fine until I added a linux NAS-box with AD
integration.

The only problem I am facing now is that the "Messenger Service" on the
DC/TS does not start anymore, EventID 2505 Source Server "The server
could not bind to the transport %1 because another computer on the
network has the same name. The server could not start.", EventID 7024
Source Service Control "The Messenger Service terminated with
service-specific error 2119".

I do not have any computers with the same name on the network except
the multihomed DC. Many solutions I find are for Win NT so I cannot use
them. Can you tell me which solutions you provided in this thread would
"repair" the messenger servic (net send)? Or do I have to apply all of
your points? (AD, profiles, group policies etc. etc. work fine)

regards

arno

 

"Ding!"
A multi-homed DC *is* two computers on the network with the same name. Each
Nic with its IP# is registered to the same Name,...hence two machines with
the same name.

You have to make sure that only one Nic gets registered with DNS.
Whatever Nic does get registered needs to be set as the first "connection"
in the Bindings.

272294 - Active Directory Communication Fails on Multihomed Domain
Controllers
http://support.microsoft.com/default.aspx?scid=kb;en-us;272294

191611 - Symptoms of Multihomed Browsers
http://support.microsoft.com/default.aspx?scid=kb;EN-US;191611

Microsoft Windows XP - Multihoming Considerations
http://www.microsoft.com/resources/documentation/windows/xp/all/reskit/en-us/prcc_tcp_qpzj.asp

I'm sure there are other articles out there as well,..but these are the only
ones I have on-hand.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed are my own (as annoying as they are), and not those of
my employer or anyone else associated with me.
-----------------------------------------------------

 

Hi Phillip,

In my case this is only true for 99%. Everything (multihomed!!) worked
fine until I replaced a linux-NAS-box in warranty and made the same
settings on the identical but new machine (machine name, ip's etc.
etc.). So, the remaining 1% is the possibility that the name of the
linux-NAS is the double name (maybe the old "name" was not deleted in
AD).

My trouble is now to find the double names on the network. Now, the
eventlog says that I can find the double name with

NBTSTAT -n

I enclosed what nbtstat -n says on my DC, does this identify the double
name?

Thank you for your links, i will also work through them.

arno


PS:nbtstat -n

LAN:
Node IpAddress: [10.1.1.1] Scope Id: []

NetBIOS Local Name Table

Name Typ Status
---------------------------------------------
MYSERVER <20> UNIQUE Registered
MYSERVER <00> UNIQUE Registered
MYDOMAIN <00> GROUP Registered
MYDOMAIN <1C> GROUP Registered
MYDOMAIN <1B> UNIQUE Registered
MYDOMAIN <1E> GROUP Registered
MYDOMAIN <1D> UNIQUE Registered
..__MSBROWSE__.<01> GROUP Registered
MYSERVER <01> UNIQUE Registered
MYSERVER <03> UNIQUE Registered

Internet:
Node IpAddress: [192.168.168.168] Scope Id: []

NetBIOS Local Name Table

No names in cache

 

Hello Ace,

I have a problem with your point 7) a).

Can you explain what to delete where? Maybe like the explaination of...

Thank you

arno

 

In

It won't register the dupe name for the additional IP because it will reject
it. If you read thru my steps, you will notice one of them says to DISABLE
Netbios on one of the interfaces to eliminate this issue.

The only reason this came to play when you put that Linux thing in is
beacause it uses NetBIOS. AD doesn't, hence why 'all of a sudden I am
getting these errors..." concerns.

Believe me, multihomed DCs are not fun to play with. If you require this
functionality, I showed you how to ALTER a DC's default functions to FORCE
it to work. Otherwise disable or remove the additonal NIC so things "just
work".

Ace

 

In

That would be in DNS. Delete the IP that you don't want. If you read the "a"
under #7, it explains and tells you what to delete. The LdapIpAddress is the
(same as parent) name. There will be one registered for every DC that exists
in a domain as well as for one for every NIC. THe instructions specifically
state to delete that, and to STOP it's DNS registration by altering the
netlogon registry entries.

I didn't say it was easy, especially if you are not familiar with AD.

Do yourself a favor, remove the additonal NIC or disable it. Things will
just work...

Ace

 

Hello Ace,

thank you for your answers. I am considering to switch to one NIC only
as I have some other network changes to make, too. So it is a good time
to do it now. (Otherwise I would maybe do nothing and forget about
net-send...)

Thank you

arno

 

In

That's the best thing I've heard you say today! One NIC!

Ace

 

Hi Ace,

just one more question:

Would DEAKTIVATING the external NIC be enough to test what the
behaviour will be with only one NIC? (I cannot remove the external NIC
because it's on the motherboard.) Or do I have to UNINSTALL it? (which
would cause the hardware wizzard to run)

regards

arno

 

Yes you can disable it.
But the one you continue to use should still be set at the top of the list
in the binding order.
The disabled one should have all the tcp config removed and set to
"automatic" before disabling the Nic.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed are my own (as annoying as they are), and not those of
my employer or anyone else associated with me.

 

thank you, I will test as you described.

arno