Multihomed DC's

Discussion in 'Server Networking' started by hedon, Jan 6, 2007.

  1. hedon

    hedon Guest

    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, and
    Internet Vlan, 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 vlan? Is
    their a better way I can design network flow, with the priority on server

    Thanks in advance for help
    hedon, Jan 6, 2007
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  2. hedon

    Bill Grant Guest

    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 interface. The only traffic using the 192.160.1.x
    interface will be traffic going to machines on the VLAN.
    Bill Grant, Jan 7, 2007
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  3. 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

    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

    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

    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):

    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]:

    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

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

    (Create this Multi-String Value under it):
    Registry value: DnsAvoidRegisterRecords
    Data type: REG_MULTI_SZ
    Values: LdapIpAddress

    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]:

    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 ( is used for illustrative

    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:

    10. If you haven't done so, configure a forwarder. You can use 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

    323380 - HOW TO: Configure DNS for Internet Access in Windows Server 2003
    (How to configure a forwarder):

    Active Directory communication fails on multihomed domain controllers

    <==*** 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]:

    Active Directory communication fails on multihomed domain controllers

    246804 - How to enable or disable DNS updates in Windows 2000 and in Windows
    Server 2003

    295328 - Private Network Interfaces on a Domain Controller Are Registered in
    [also shows DnsAvoidRegisterRecords LdapIpAddress to avoid reg sameasparent
    private IP]:

    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]:

    825036 - Best practices for DNS client settings in Windows 2000 Server and
    in Windows Server 2003 (including how-to configure a forwarder):;en-us;825036

    291382 - Frequently asked questions about Windows 2000 DNS and Windows
    Server 2003 DNS;en-us;291382

    296379 - How to Disable NetBIOS on an Incoming Remote Access Interface
    [Registry Entry]:

    Rid Pool Errors and other mutlhomed DC errors, and how to configure a
    multihomed DC, Ace Fekay, 24 Feb 2006


    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 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

    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...
    Ace Fekay [MVP], Jan 8, 2007
  4. hedon

    Bill Grant Guest

    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.

    Bill Grant, Jan 8, 2007
  5. 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 Fekay [MVP], Jan 9, 2007
  6. hedon

    arno Guest

    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

    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)


    arno, Jan 9, 2007
  7. "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

    191611 - Symptoms of Multihomed Browsers;EN-US;191611

    Microsoft Windows XP - Multihoming Considerations

    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]

    The views expressed are my own (as annoying as they are), and not those of
    my employer or anyone else associated with me.
    Phillip Windell, Jan 9, 2007
  8. hedon

    arno Guest

    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

    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

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


    PS:nbtstat -n

    Node IpAddress: [] 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

    Node IpAddress: [] Scope Id: []

    NetBIOS Local Name Table

    No names in cache
    arno, Jan 10, 2007
  9. hedon

    arno Guest

    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, Jan 10, 2007
  10. 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

    Ace Fekay [MVP], Jan 10, 2007
  11. 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 Fekay [MVP], Jan 10, 2007
  12. hedon

    arno Guest

    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

    Thank you

    arno, Jan 11, 2007
  13. In
    That's the best thing I've heard you say today! One NIC! :)

    Ace Fekay [MVP], Jan 12, 2007
  14. hedon

    arno Guest

    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)


    arno, Jan 15, 2007
  15. 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]

    The views expressed are my own (as annoying as they are), and not those of
    my employer or anyone else associated with me.
    Phillip Windell, Jan 15, 2007
  16. hedon

    arno Guest

    thank you, I will test as you described.

    arno, Jan 16, 2007
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