How to configure Windows 2003 as a Router ?

Discussion in 'Server Networking' started by Peter, Apr 30, 2007.

  1. Peter

    Peter Guest

    I am new to networking and would like to seek your advice.

    We would like to configure a Windows 2003 Server as a router between 2

    There are already 2 NICs and each of them is assigned IP address of
    different subnets.

    We would like to know is it necessary for us to install any service (like
    RRAS) to achieve our need ? Besides, does it mean that the default gateway
    for those workstations connected to that Windows 2003 Server will use its IP
    address as default gateway ?

    Thank you for your help.

    Peter, Apr 30, 2007
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  2. Peter

    Jeremy Guest

    You'll need to configure RRAS. Simply select it from the Admin Tools menu
    and use the help to get it working.

    Assuming a simple network with the only way out of the network being via the
    WS03 box, then you will need to set the default gateway for the workstations
    to be the network interface of the server. Keep in mind that devices on the
    other side of the server that is acting as the router need to have a static
    route for the workstation subnet that goes back through the WS03 RRAS server
    in order for return traffic to come back to the workstation.

    I hope this is clear.

    Jeremy, Apr 30, 2007
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  3. Peter

    Bill Grant Guest

    It is possible to allow IP routing without using RRAS, but it is pretty
    pointless. Simply configure RRAS to be a LAN router from the wizard and it
    will do it for you.

    As Jeremy pointed out, all this does is configure the machine so that it
    can forward traffic from one subnet to the other. Whether it routes or not
    depends on how the two subnets are configured.

    If all you want to do is link these two subnets, the routing is trivial.
    You simply make the RRAS router the default gateway for both subnets. eg

    192.168.1.x dg
    | dg blank
    RRAS dg blank
    192.168.2.x dg

    Any traffic which is not local (ie not in the same IP subnet) is sent to
    the router. The router can deliver it in the other subnet because it has an
    interface in that subnet (ie the target machine is local to the router).

    Usually the setup is not as simple as that. One subnet is usually using
    some other router, such as an ADSL Internet device as its default gateway.
    Simply enabling IP routing doesn't do much because the trafffic never gets
    to the RRAS router. You need extra routing to get the traffic to the correct
    router. If you are in that situation and can't see what extra routing you
    need, post a description of how your network is set up.

    PS. I hope this server is not a DC. Using a DC as a router is not recomended
    and it may cause you all sorts of odd problems.
    Bill Grant, May 1, 2007
  4. Peter

    Peter Guest

    Dear Bill,

    Thank you for your advice.

    The reason why we consider this option is because our Network Officer says
    that by using a Windows 2003 Server as a router for connecting machines in
    headquarter to a remote site.

    I just wonder whether it is a good idea as the single point of failure will
    be the Windows 2003 Server and the 2 NIC.

    Peter, May 1, 2007
  5. Peter

    Bill Grant Guest

    Whatever device you use as a router, it is going to be a single point of
    failure unless you have a very complicated routing setup with multiple

    How are you planning to connect HQ to a remote site? Leased lines or
    Bill Grant, May 1, 2007
  6. Peter

    Peter Guest

    It is planned to use leased line.


    Peter, May 2, 2007
  7. Peter

    Bill Grant Guest

    OK. As I said in a previous post, the important thing about routing is
    getting the traffic to the correct router. If this RRAS router is an
    additional router in a subnet which currently uses some other device as the
    default gateway (ie default router) the traffic for the other site may never
    get to the RRAS router unless you add extra routing to the LAN. It only
    works automatically if there is only one gateway and it is set as the
    Bill Grant, May 3, 2007
  8. Peter

    Peter Guest

    Dear Bill,

    There is default gateway in headquarter and remote site. However, the
    network guy says that in order to get both sites get connected with the new
    lease line, he has to remove the default gateway at remote site and make use
    of the Windows 2003 Server as router here.

    In this way, I believe that machines in remote site will regard the Windows
    2003 Server as default gateway while machines here will continue to use the
    existing default gateway (CISCO Router).

    Is there any adjustment has to be done ?

    Peter, May 3, 2007
  9. It doesn't matter what router is used for the Default Gateway as long as the
    router that is used "knows" how to get to everything else. So the network guys
    are "partially" correct, but they may have too narrow of a view of it.

    The Default Gateway of the hosts on any particular subnet should be the router
    that has the most "knowledge" about the rest of the LAN/WAN. That "knowledge"
    may or may not be accomplished by Dynamic Routing Protocols between the routers.

    Phillip Windell

    The views expressed, are my own and not those of my employer, or Microsoft, or
    anyone else associated with me, including my cats.
    Phillip Windell, May 3, 2007
  10. Robert L. \(MS-MVP\), Nov 29, 2008
  11. Peter

    Bill Grant Guest

    You can certainly use Windows Server as a LAN router between two LAN
    segments, and these two segments can be of different types. The server
    network will run at IGb and the other at 100Mb.

    Just installing RRAS and enabling LAN routing will probably not get
    routing working. It only works automatically if the router is the default
    gateway for both networks. If one network is connected to the Internet and
    all machines use the Internet router as the default gateway, no traffic will
    ever go to the internal router.

    There are a couple of options. If the LAN machines need to initiate
    connections to the servers (but not vice versa) you can use NAT. If you need
    full interaction (ie the servers can initiate connections to the other
    machines) you use standard LAN routing plus static routes. eg

    NAT setup

    gateway router
    10.1.1.x dg
    | dg
    RRAS/NAT dg blank
    LAN machines
    192.168.31.x dg 192.168.31.x

    Fully routed setup

    gateway router {static route}
    10.1.1.x dg
    | dg
    RRAS dg blank
    LAN machines
    192.168.31.x dg

    The NAT method works because all traffic from the inner subnet is using
    the NAT router's 10.1.1 address in the outer subnet (because of address
    translation in NAT).

    In the second case the traffic from the inner subnet is using the
    192.168. IP address, so the gateway router must know how to reach the inner
    subnet (via the NAT router).
    Bill Grant, Nov 29, 2008
  12. Hi,
    i dont see the clear advantage if all traffic passes the wire to / and from
    the router to the switch.

    first you should know how the serverfarm itself operates ? especially do
    they communicate with each other ?

    Juergen Kluth, Dec 1, 2008
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