Re: issue with DC replication


Hi Ace,

Thanks for the suggestion.
As per your suggestion I have set up one NIC for name resolution and still I
am not able to achieve what
I am really looking for.

is there any mechanism there to switch over straight away from the preferred
DNS server to
other DNS before taking down ,the one which is providing name resolution
service.

Testing Network Scenario:

1)2 On-Line Web Servers.(Web 01 and web 02)-Clustered using NLB.
2)2 DNS Servers.(DC-01&Dc-02).---Both are AD-I.

PS: what happens if the DNS Server running on a different subnet other than
web boxes.

Regards
Mill




"Ace Fekay [Microsoft Certified Trainer]" wrote:

"millin" <ssuj@xxxxxxxxxxxxxxxxxxxxxxxxx(No Spam)> wrote in message
news:AD7593F3-8D12-4FE9-92AA-97EB5E979B8B@xxxxxxxxxxxxxxxx
Hi Jorge,

There is no way I can run these cmd's in the live boxes.
Company policy doesn't allow me to do that.

I got the permission to set up a test network for finding the issue.
I got no idea what I needed and how i am supposed to do it?



Hi Mill,

As Jorge stated and explained why, multiple NICs on a DC is not recommended
nor advised. All engineers will agree with both of us on this. Multiple NICs
on a DC can cause numerous issues, starting with replication, to clients not
able to logon, authentication failing, etc, due to the DNS registrations of
the multiple interfaces. And simply unchecking the 'register this
connection' in NIC properties, doesn't do the trick. It would require
registry and other changes to control registration, essentially altering the
DC's functionality to make it work for a multihomed DC.

The folloiwng is a little write-up I've created on this subject, which
encompasses multiple scenarios with multihomed DCs, as well as how to alter
your DC to properly function with multiple NICs and/or IPs. I hope it helps.
======================================================================================================
Multihomed DCs, DNS, RRAS servers.
By Ace Fekay, MCSE, MCT, former Directory Services MVP
First published: January, 2003, revised accordingly
==============================================

Multihomed DCs WILL cause numerous issues. It's highly recommended to single
home all DCs and use a non-DC for the multihoming purposes. If it is the
internet gateway, it is recommended to purchase an inexpensive, or cable/DLS
router, or even better, a Cisco or similar firewall to perform the task,
which if it is compromised by an internet attacker remotely, can further
compromise the rest of the internal network.

Also if attempting to use ICS on a DC, this further complicates matters with
DC functionality, and cannot be fixed with the following steps outlined in
this article.

To explain why will require a 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. I usually see
errors (GPOs not working, can't find the domain, RPC issues, etc), when the
ISP's DNS servers are listed on a client, DCs and/or member servers, or with
multihomed DCs. If you have an ISP's (or some other outside DNS server or
even using your router as a DNS server) DNS addresses in your IP
configuration (all DCs, member servers and clients), they need to be REMOVED
and ONLY use the internal DNS server(s). This can be very problematic.

Basically, AD requires DNS. DNS stores AD's resource and service locations
in the form of SRV records, hence how everything that is part of the domain
will find resources in the domain. If the ISP's DNS is configured in the any
of the internal AD member machines' IP properties, (including all client
machines and DCs), the machines will be asking the ISP's DNS 'where is the
domain controller for my domain?", whenever it needs to perform a function,
(such as a logon request, replication request, querying and applying GPOs,
etc). Unfortunately, the ISP's DNS does not have that info and they reply
with an "I dunno know", and things just fail. Unfortunately, the ISP's (or
your router as a DNS server) DNS doesn't have information or records about
your internal private AD domain, and they shouldn't have that sort of
information.

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 or simply use the internal networking
routing to allow access. Here's the whole list of manual steps to follow.

Another problem is the DC now becomes part of two Sites. This is another
issue that can be problematic.

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. If the both NICs are
internal, I would suggest to pick a subnet, team the NICs and allow your
internal routers handle the traffic between subnets - 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 DNS
http://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/treeview/default.asp?url=/technet/prodtechnol/windowsserver2003/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? Good question. 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

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/?id=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 multihomed DC errors, and how to configure a
multihomed DC, Ace Fekay, 24 Feb 2006
http://www.ureader.com/message/3244572.aspx

257623 257623 Domain Controller's Domain Name System Suffix Does Not Match
Domain Name
http://support.microsoft.com/?id=257623
==========================================


--
Ace

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

Please reply back to the newsgroup/forum to benefit from collaboration among
responding engineers, as well as to help others benefit from your
resolution.

Ace Fekay, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSA Messaging, MCT
Microsoft Certified Trainer
aceman@xxxxxxxxxxxxxxxxxxxxxxx
http://twitter.com/acefekay

For urgent issues, you may want to contact Microsoft PSS directly. Please
check http://support.microsoft.com for regional support phone numbers.


.

Relevant Pages

  • Re: Urgent! New router and big disaster
    ... Both NICs should point to his internal IP for DNS. ... forward ports to it reliably in the router. ... I should have been more clear about internet connection.. ...
    (microsoft.public.windows.server.sbs)
  • Re: Seeking info about best practice for multihomed (or not) DCs
    ... advisable to use multihoming on a DC. ... Unteamed NICs in a DC is inviting trouble, ... Prior to making any registry modification, ... Multihomed DCs, DNS, RRAS servers. ...
    (microsoft.public.windows.server.networking)
  • Re: Seeking info about best practice for multihomed (or not) DCs
    ... Unteamed NICs in a DC is inviting trouble, ... Prior to making any registry modification, ... Multihomed DCs, DNS, RRAS servers. ... In the DNS console, right click the server name, choose properties, then ...
    (microsoft.public.windows.server.networking)
  • Re: Urgent! New router and big disaster
    ... Both NICs should point to his internal IP for DNS. ... You should give your SBS a fixed external address so you can forward ports to it reliably in the router. ... I should have been more clear about internet connection.. ...
    (microsoft.public.windows.server.sbs)
  • Re: Seeking info about best practice for multihomed (or not) DCs
    ... like to reiterate that a multihomed DC is not advisable unless the NICs ... registry entries to be modified. ... Multihomed DCs, DNS, RRAS servers. ... A standard Windows service, called the "Browser service", provides ...
    (microsoft.public.windows.server.networking)