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Thread: configuring multihomed server

  1. #1 Guest

    configuring multihomed server

    I would like to know if you need to have RRAS services installed and/
    or a configured routing table if a Windows Server 2003
    server is multihomed. Is it possible to just use 2 or more network
    adapters on the
    server without the server having to be configured as a router? Any
    help or links to documents about this would be most appreciated.

  2. #2
    Ace Fekay [MVP] Guest
    It all depends on what you need it for. Will it be routing between two
    subnets? Then yes, you need RRAS. Will it be used as a NAT? Yes, you'll need
    RRAS. Will it be a VPN server for outside clients to VPN into the sytem
    with? Then yes, you need RRAS here too. And no, for a VPN server, you do not
    need multiple NICs, but then again, it depends on what you need it for.

    However, if this server is a domain controller, then you really really do
    NOT want to multihome it. The additional NIC causes numerous issues if the
    DC is not configured properly with the multiple NICs. I'm not trying to stop
    you, but highly suggest not to. If you really want to, I do have a set of
    instructions I can provide to assist you in properly configuring a
    multihomed DC that involves a couple of reg changes, etc. Let me know if
    this is the case.

    However, if you want the multi NICs to increase network performance and laod
    balancing, then you can install the appropriate NIC drivers from the
    manufacturer and team them. This is good with a DC too.

    I just saw your ost after asking pretty much the same question. I'm
    interested in any information regarding configuring a multihomed DC for NAT
    and to segment a network (two separate networks).

    I really do not recommend it because the settings alter default DC
    functionality inorder to make it work for what you want. It's better to get
    a firewall like a Cisco PIX or similar to do the trick and let the DC do
    it;s job.

    Here's what I mean... happy reading...

    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
    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

    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

    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

  3. #3 Guest
    It definitely sounds like
    multihoming a DC is not worth the hassle, but I would like to clarify
    one point since I am relatively new to networking. It sounds like if
    you are connecting two or more different networks or subnets with a
    multihomed Windows server performing any role whatsoever, then that
    server needs to have RRAS installed and be configured as a router. Is
    this correct, or can you somehow connect two subnets with a dual-homed
    server and not need routing installed?

    Could either of you point out a link where I might get instructions
    for setting up a workstation or server for routing using the method of
    enabling routing in the registry? In particular, would I need to
    manually configure a routing table?

  4. #4
    Ace Fekay [MVP] Guest
    As long as it's not a DC, no worries. The problem with a DC and multi NICs
    is multiple DNS registration. This the main concern, especially if RRAS
    comes into the picture on a DC because now you have the RRAS IPs
    registering. If a client is now looking for the DC (especially if it is a
    GC), can it get to it from any of the IPs that may answer using Round Robin?
    This is just the tip of what can go wrong. That's why it's basically not
    worth the effort with a DC.

    For what you are saying, multiple NICs on a member server, or a workstation,
    as Bill points out, is fine.

    How To Set Up Routing and Remote Access for an Intranet in Windows Server
    2003 Enterprise Edition and Windows Server 2003 Standard Edition;en-us;323415

    Depending on your network, you may need to build a static route table,
    unless the current routers are using a prototocol to broadcast is such as
    OSPF or RIP, which Win2003 supports. How big of an infrastructure are we
    talking about here? Is NAT involved? Lay out an example of what you are
    trying to do. There are too many variables for a simple yes/no answer when
    it comes to RRAS and routing.

  5. #5
    Andrew Hayes Guest
    I don't know the OP's requirements, but from what has been said in this
    thread, it looks like you could help me.

    Currently, I have a single subnet (eg. 192.168.0.x) which I'll call LAN1,
    and I wish to add 2 more subnets (eg. 192.168.1.x and 192.168.2.x) which I'll
    call LAN2 and LAN3.

    This is to allow me to setup a staging environment that duplicates the real
    environment (where LAN1, LAN2 and LAN3 make a WAN through IP-VPN).

    From what I've read of routing, all I need is a desktop if I want to use IP
    Routing only, although I'd rather use RRAS so I can simulate the dial-in VPN
    users as well at a later stage.

    To accomplish this I would need a server with 3 NIC's. Each one has a fixed
    IP for each of the 3 subnets (NIC-LAN1, NIC-LAN2, NIC-LAN3 for examples sake).

    Up to this point I think I understand it.

    The next part is configuring RRAS so that a desktop in LAN1 can use TS to
    connect to a server in LAN2 or LAN3, and that a server in LAN2 or LAN3 can
    use TS to connect to a server in LAN3 or LAN2, respectively.

    Could one of you networking boffs explain how I need to setup the RRAS?
    Either using a wizard, or manually.

    Just to clarify the settings, here is what I did (feel free to skip to the
    end as I've included most of the steps for the benefit of others).

    I run Adminsitrative Tools | Routing and Remote Access tool, then I
    right-click on my SERVER, and choose the "Configure and Enable Routing and
    Remote Access..." which brings up the "Windows Firewall/Internet Connection
    Sharing service is enabled for SERVER..." message.

    Closed that dialog, then went to Adminstrative Tools | Services tool and
    stopped the "Windows Firewall/Internet Connection Sharing (ICS)" service,
    then went to the service Properties and set it's "Startup type" to Disabled.

    Go back to Routing and Remote Access and choose Configure and Enable again.
    Up pops the RRAS setup wizard.

    Selected "Custom configuration" and hit Next, choose "LAN Routing" only and
    hit Next, then Finish. When it asks me if I want to start the service, I
    click Yes.

    In the tree, under Network Connections, I see Loopback, LAN1, LAN2, LAN3 and
    Internal. All Connected and all Enabled.

    Under IP Routing | General, I see Loopback (, Up), LAN1
    (, Up), LAN2 (, Up), LAN3 (, Up) and
    Internal (Not available, Unknown).

    IPCONFIG looks like this:

    Windows IP Configuration

    Ethernet adapter LAN1:

    Connection-specific DNS Suffix . :
    IP Address. . . . . . . . . . . . :
    Subnet Mask . . . . . . . . . . . :
    Default Gateway . . . . . . . . . :

    Ethernet adapter LAN2:

    Connection-specific DNS Suffix . :
    IP Address. . . . . . . . . . . . :
    Subnet Mask . . . . . . . . . . . :
    Default Gateway . . . . . . . . . :

    Ethernet adapter LAN3:

    Connection-specific DNS Suffix . :
    IP Address. . . . . . . . . . . . :
    Subnet Mask . . . . . . . . . . . :
    Default Gateway . . . . . . . . . :

    Is that all I need to do, or do I need to setup Static Routes?

    This is the one that caused me a few problems, which I have resolved, but I
    am including the details so that others may glean some insight.

    We also have another LAN on a different WAN (for arguments sake we'll call
    it LANX - 192.168.3.x), and most machines on LAN1 use the H/W router
    ( -> Leased Line -> to LANX as the default
    gateway, as LANX is a data center that contains the corporate servers (shared
    folders, email, etc.).

    However, the LAN2 and LAN3 machines have no need to connect to LANX, hence
    why I didn't include it in RRAS.

    Anyhow. The offshoot of this was that the desktops on LAN1 that need access
    to LANX, as well as the staging servers in LAN2 and LAN3, had to have their
    Default Gateway removed and then persistant static routes added to their
    routing tables in order to access resources on both LAN1 and LANX.


    Once that was all done everything was hunky dory. However, I do not know if
    this is the best way to go about it. I just know it works. Any further

    A little tool to help check line width.

  6. #6
    Bill Grant Guest
    In theory you do not need RRAS. You do not even need a server OS. You can
    use a workstation as a router by putting two NICs in it, connecting them to
    two different networks and enabling IP routing in the registry.

    RRAS is a pretty complete router and remote access server and it has
    builtin wizards to configure it for most common tasks. If you configure it
    as a LAN router only, it just enables IP routing.

    Enabling IP routing allows the machine to forward traffic arriving on
    one interface to be sent on through the other interface. The simplest case
    is a setup like this.

    192.168.1.x dg
    | dg blank
    router dg blank
    192.168.21.x dg

    Machines in either subnet can communicate directly "on the wire"
    using hardware addressing. Traffic for a machine in the "other" subnet will
    be sent to the default router (because it is not in the local subnet). If IP
    routing is enabled, the router can deliver this traffic directly in the
    "other" subnet from its other NIC.

    No, you do not need to configure anything in the routing table. A machine
    will automatically set up a route to handle the subnets used by the NICs
    attached to the router. All you need to do is enable IP routing in the
    registry. If the machines on each side of the router use the router as their
    default gateway, everyting just works.

    Here is the KB explaining how to enable IP routing in XP.

    It certainly isn't a very elegant solution. I don't like the idea of
    putting static routes on workstations. It is better to configure your
    network so that the routers actually do the routing.

  7. #7
    Join Date
    Jun 2010

    Re: configuring multihomed server

    I needed to configure my two DC's (which already had back-end nic's installed but weren't connected to anything) to talk to my new SAN. First attempt failed as I forgot about the preliminary steps needed to prevent them from causing havoc with AD and DNS. So I had a little havoc going on.

    Your info was helpful but ultimately I followed the steps outlined here to configure the NIC's and simply scoured my DNS (based on your info) which was already configured to listen on specific interfaces, for any references to the back-end nics and all is fine.

    I now have two multihomed DC's talking to my SAN (via the storage LAN) and User LAN without issues.

    I also want to say that there are times when a multihomed DC is unavoidable, such as in my case where I inherited a network with a DC running Exchange which is low on drive space. Ultimately it is easier to configure a set of back-end NICS and connect it to the SAN and move the Store rather than stand up another server and move the Exchange installation. I am currently in the process of virtualizing and will correct these faux pas' as I go but I gotta keep the hamsters runnin' for now.

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