2 Gateway's on 1 NIC on Windows Server 2003

Discussion in 'Server Networking' started by Jwolfer, Apr 27, 2005.

  1. Jwolfer

    Jwolfer Guest

    Greetings all,

    Here is my situation.

    I have 2 internet connections to our company.

    1. Comcast Cable Service
    2. A local ISP DSL

    This is necessary due to the fact that since we host our own mail server, we
    need to have reverse DNS resolution. Something Comcast does not offer. Only
    in/out bound email travels through the DSL. All other web traffic uses

    My company network has ip info such as:


    I have a linksys router on the dsl service that routes packets to our
    server. My server has 1 NIC in it.

    Because the router has an IP addy of 1.250, I need to designate the Gateway
    of 1.250

    So, while the network clients point to 1.1 for a gateway, my server uses
    1.250 for its gateway. This is presenting a problem when communicating with
    that server. If a client with 1.1 connects to it, some small probelems

    Is there an effective way to give 2 gateways to 1 NIC, or maybe even 2 NICs?
    I have tried to enter the second gateway number (1.250) in, and give it a
    metric of 2, while giving 1.1 a metric of 1. But none of the SMTP traffic
    comes through.
    Jwolfer, Apr 27, 2005
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  2. No,...almost always,...but sometimes,... yes. I don't understand what you
    are attempting well enough to say. Can you explain in a more focused way
    what you are trying to do.

    I don't want to know about clients pointing here and there and this pointing
    there and that point here. What I want to know is:.......

    You have two INet connections:

    1. Comcast Cable Service
    2. A local ISP DSL

    What do you want to do with each one specifically?

    How does each one connect to your LAN? Using the same device? Separate

    What Servers are involved and where/how are they *physically* located with
    respect to these two Connections?
    Phillip Windell, Apr 27, 2005
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  3. Jwolfer

    Jwolfer Guest

    Sorry about that.. I sorta figured I wasn't describing this well.

    Here is a link to a JPG image outputted from visio of our network topography.


    If you look at the diagram, you will see that on the right side (corporate
    office), we have 2 Inet connections coming in. Each has a different

    The Planetcable DSL line comes in, hits the linksys firewall (who's IP is and forwards any smtp packets through port 25 on to the AV
    Server (which is our company Anti Virus Server), where it is then scanned and
    forwarded onto our SMTP email server.

    The problem is, the AVServer ( needs to connect to the linksys router gateway, as well as the rest of our network.
    The rest of the network uses as its gateway.

    Essentially, AVServer does not see Davinci. It sees, but not
    the DNS name Davinci.

    So, I would like to have 2 gateways set up on the AVServer, 1 for the
    linksys router side (1.25), and 1 for the rest of the network (1.1)

    That help?
    Jwolfer, Apr 27, 2005
  4. Excellent! If everyone gave a diagram like that life here would be so easy
    it would be a sin!
    1. Get rid of the second Nic in the AV Server. Adjust the PlanetCable box to
    pass the SMTP to instead of
    2. Plug *both* DSL Devices into the Switches. Do not plug the PlanetCable
    box into the AV server directly as the diagram shows.
    3. The AV Server will use the PlanetConnect Box as the Default Gateway (It
    is the only machine that does). It will never use the ComCast box, don't
    worry about it,...it is irrelevant.
    4. All the other machines will use the ComCast Box as the Default Gateway.
    They will use the PlanetConnect box to get to the Corp LAN due to my next
    comment, #5.
    5. On the ComCast box, add a Static Route that tells it to use
    as the Gateway to
    Your duel nics is causing this. If you do what I described above then this
    problem won't even exist to begin with.

    For futher details concerning DNS,...you should have you DNS setup as
    described below,...if you aready do, then good,...if not, you'd better
    change it.

    All devices,..everything,... must use your Active Directory DNS Server as
    thier DNS Server,...and only that server(s). Your ISP's DNS (nor the DSL
    Devices) should ever appear in any of the network settings of any device on
    your LAN,...ever.

    Then,...within the configuration of the AD DNS Server itself find the
    Forwarder List.

    MMC--> Servername ---> Properties ---> Forwarders Tab

    List the ISP's DNS Server(s) here.
    Phillip Windell, Apr 28, 2005
  5. Jwolfer

    Jwolfer Guest

    Sorry for the delayed response. I rolled out exchange server last week, so
    this got put on hold.

    I feel that I am right with you on the theory of this... but just not sure
    how to actually accomplish it.

    You are saying to add a static route on davinci? or on avserver?

    remote users are using for a gateway, coming through the VPN,
    hitting the comcast modem, and then the pix firewall/vpn. Then they hop onto
    our network just like veryone else.

    So, which server do I need to add the static route to?
    Jwolfer, May 9, 2005
  6. Static routes only effect "1 hop" so the Static route goes on the device
    that immediately preceeds the "next hop". In other words it goes on the
    Device that has to make the decision, and decisions are always asking "what
    is the next hop?",...not... "what is the hop after the next hop?"
    Phillip Windell, May 9, 2005
  7. Jwolfer

    Jwolfer Guest

    Next hop from who to who?

    This is where I am confused.

    The pix firewall sits on the same switch as the servers. So does the switch
    need to be configured for routing?

    I guess I didn't understand as much as I thought.
    Jwolfer, May 9, 2005
  8. Jwolfer

    Neteng Guest

    A switch can't route (lets keep the layer3 switch out of this one). You need
    the default gateway to be the inside address of your PIX. Philip is correct
    in what he stated, but I'll try and explain it another way. Let's say you
    have three routers in a line. If your on router 1 and you want to get to
    router 3, you will have to go through router 2. If you set your default
    gateway to router 3 you may or may not get there. Why? If router 2 knows how
    to get to router 3, you'll be OK. If router 2 doesn't know how to get to
    router 3 your traffic will die there. No matter what route statements you
    put in router 1, you'll never get there if router 2 does not know how to get
    there. A good test is from router 1 do a traceroute to router 3 and see if
    it crosses router 2. If it does router 2 it knows where to go! If it fails,
    either router 1 or router 2 does not where to go. The next step is get on
    router 2 and ping router 3. If it pings, it knows how to get there and the
    problem is on router 1. If it can't get there, look at the route table
    because the problem is on router 2.
    BTW I've never seen a windows box that has two IP's on one NIC that can
    route off it's configured subnets. If you get it working, please post for
    the rest of us.

    Neteng, May 9, 2005
  9. Jwolfer

    Jwolfer Guest

    I understand all of that, but I appreciate your reply.

    What I am getting from all of this, is I need to have 1 NIC enabled on this
    particular server.

    It has the IP

    Clients who have an IP of and a GW of can see the
    server just fine. Clients who have an IP of and a GW of cannot.

    So essentially, any PC with a GW of cannot see a gateway of

    I need to know how do a static route that fixes that.
    Jwolfer, May 9, 2005
  10. Jwolfer

    Neteng Guest

    I need a little more background. What is the device (router/firewall) at Why do your clients have a different gw than your server? Is
    the server supposed to be their gw? How does the 192.168.10.x network
    connect to 192.168.1.x network (does this connect to the same router as or is this your secondary IP on the server or ....)?
    Neteng, May 9, 2005
  11. Jwolfer

    Jwolfer Guest

    Here is a network diagram.


    We have 2 ISP connections. 1 Comcast Cable and 1 PlanetCable DSL

    The reason for this is that comcast will not reverse resolve our Mail
    Server's IP address/and/or name. So we use a local isp to handle our email
    routing and dns service.

    Comcast has the speed though, so that is what we have our VPN tunnel coming
    in through, as well as all internet activity and FTP.

    Essentially what is going on here is... for my AV server to process incoming
    email for virus control and spam filtering, it is has to have the same
    gateway as the router connected to the DSL modem (1.250)... and NOT that of
    the router connected to the Cable modem (1.1).

    All clients point to the gateway of the cable modem (1.1)

    My clients at our remote office have a gateway of their router connected to
    their internet connection (10.1)

    10.1 can see 1.1 just fine. 1.1 can see 1.250 just fine, but 10.1 cannot
    see 1.250 at all.

    I currently have 1 NIC in my AV server. Its connected to the same switch
    that my 2 routers are connected to. So, to direct traffic in/out of the DSL
    line, it has to have the same GW IP as the router connected to the DSL line

    The problem is, my 10.x clients cannot see my AV server (cannot even ping
    it) since the AV Server is on 1.250

    Hope that helps.
    Jwolfer, May 10, 2005
  12. Jwolfer

    Neteng Guest

    OK, from the AVServer, you can not ping anything on 192.168.10.x correct? It
    only has two routes, one for the local subnet, 192.168.1.x and one default
    route for all other traffic, pointing to (I know you
    know this, just keeping it straight in my head). To get to the 192.168.10.x
    network, you need the following static route in the AVServer.

    route ADD MASK -p

    The -p is to set it persistent, so it won't disappear after a reboot. Try
    this and let me know how it goes.
    Neteng, May 10, 2005
  13. Jwolfer

    Jwolfer Guest

    THis fixed the problem. Thanks a million for your help! And now I have a
    better understanding of how this all works. Thanks everyone!
    Jwolfer, May 10, 2005
  14. Jwolfer

    Neteng Guest

    good to hear

    Neteng, May 10, 2005
  15. You never fixed to one huge issue that I told you to correct several weeks
    ago, unless you just haven't updated the diagram.

    The physical link that runs directly between the PlanetCable DSL Device and
    the AV Server must be eliminated.

    The AVServer must run only one Nic (

    Both DSL Devices must connect into the LAN at Layer#2 (the Switches) just as
    the Comcast DSL Device is already doing.

    The AVServer,... according to your requirements last time we dealt with
    this,...must use the PlanetConnect DSL Device ( as it Default

    All other machines except for the AVServer must use the Comcast Device as
    their Default Gateway ( The machines then will all need
    (except the AVServer) a Static Route that uses at the
    "gateway" to network 192.168.10.*

    "C:\> Route add mask -p"
    Phillip Windell, May 10, 2005
  16. Jwolfer

    Neteng Guest

    That's incorrect. Your adding an additional hop. Also, you should never
    create a static route on all the client PC's. Your telling all client
    traffic, if you want to get to 192.168.10.x go to the Planet router. The
    Planet router hopefully has a route to 192.168.10.x, but maybe not. Let's
    assume it does (that route would be
    The Planet router then forwards all traffic for 192.168.10.x to the Comcast
    Router because it's the VPN endpoint and knows about that remote subnet. Now
    let's say the AVServer is only connected to the Planet router and not the
    access switch. You would want to create a host route on the routers for

    Neteng, May 10, 2005
  17. No it isn't. There is no additonal hop,...it is just that all the machines
    (except the AVServer) normally use the Comcast Device for Internet traffic,
    but to get to the Remote Office ( they have to use a different
    Gateway than the Default,....So,...it isn't an additional Hop, it is just
    using a different gateway,...that is not the same thing. It would only be
    an additional Hop if it went through the Comcast Device to get to the
    PlanetCable Device, but that is not what it is doing.
    That's my line. I'm always telling people that. :)
    Yes,...if the ComCast Device can except "Static Routes" then you could place
    just the one static route only on the ComCast Device telling it that all
    traffic to uses If it can do that, great,
    excellent,..that is the best way to go and you only have to worry about one
    static route on one device,...but I don't know that it is capable of doing

    It does. That is one of its primary reasons to exist.
    The AVServer has two Nics with one connected to the PlanetCable Device and
    one Nic connected to the LAN Switch. Both Nics are in the same subnet (the
    diagram just doesn't show both addresses). That is a bad design. It should
    only have one NIC. The original intent was that the AV Server use the
    PlanetCable Device for Internet Access instead of the Comcast one. All other
    machines are supposed to use the Comcast Device instead of the PlanetCable
    Device. What I suggested both then and now does exactly what is supposed to
    be done,...the only question is if the Comcast Device can accept static
    routes or not,....if it can,... then add the "route" there,..if not,..then
    it has to be done on every individual machine becuase there is no "LAN
    Router" since the LAN is a single subnet (

    He and I have dealt with this quite some time ago, so I am familiar with the
    context he is dealing with. Ironically I had just thrown out the printouts
    of the diagram this morning because I didn't think I would need them anymore
    and they had been cluttering my desk for that last week or so.
    Phillip Windell, May 10, 2005
    Phillip Windell, May 10, 2005
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