Multiple network adapters

Windows 2003 two nics two gateways   
Windows 2003 and 2 nic's trying to route between different subnets.
I do not think that you can achieve your requirement by any software application, as meniolf suggested; you need to think about manageable switches to configure subnet/VLAN.
=============================
DC with 2 NICs and DNS resolving in the different subnets
DNS configuration best practice on DC and clients/member servers:
== MULTIHOMING Domain controllers is not recommended, it always results in multiple problems.
1. Domain Controllers should not be multi-homed
2. Being a VPN Server and even simply running RRAS makes it multi-homed.
3. DNS even just all by itself, is better on a single homed machine.
4. Domain Controllers with the PDC Role are automatically Domain Master Browser. Master Browsers should not be multi-homed
272294 - Active Directory Communication Fails on Multihomed Domain Controllers http://support.microsoft.com/default.aspx?scid=kb;en-us;272294
191611 - Symptoms of Multihomed Browsers
http://support.microsoft.com/default.aspx?scid=kb;EN-US;191611
== DNS configuration on domain controller:
1. Each DC / DNS server points to its private IP address as primary DNS server and other internal/remote DNS servers as secondary DNS in TCP/IP property.
2. Each DC has just one IP address and one network adapter is enabled (disable unused NICs).
3. If multiple NICs (enabled and disabled) are present on server, make sure the active NIC should be on top in NIC binding.
4. Contact your ISP and get valid DNS IPs from them and add it in to the forwarders, Do not set public DNS server in TCP/IP setting of DC.
== IP configuration on clients and member servers:
 1. Each workstation/member server should point to local DNS server as primary DNS and other remote DNS servers as secondary.
2. Do not set public DNS server in TCP/IP setting of client/member server.
Once you are done with above, run "ipconfig /flushdns & ipconfig /registerdns", restart DNS server and NETLOGON service on each DC.
--------------------------------------------
running DCs multihomed is bad configuration and should NEVER be used
Why is this crappy setup chosen from you? Anyway, please remove on each DC one NIC, cleanup DNS zones and run ipconfig /flushdns and ipconfig /registerdns and restart the netlogon service. See Ace's article why NOT using this:
http://msmvps.com/blogs/acefekay/archive/2009/08/17/multihomed-dcs-with-dns-rras-and-or-pppoe-adapters.aspx
Use switches that provide VLANs and then divide the subnets that way.
==================================
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Multiple network adapters

Network Load balancing can use multiple network adapters in two different and distinct ways. The first use is to create multiple Network Load Balancing clusters; achieved by binding Network Load Balancing to each of the multiple adapters.
The second use for multiple network adapters is to use one or more adapters for handling cluster traffic, but also configure at least one adapter to be used for server management. The management adapter does not handle cluster traffic. Further information on this this second use of multiple network adapters is described below.

Multiple network adapters in unicast mode

In unicast mode, the cluster's media access control (MAC) address is assigned to the network adapter that is functioning as the cluster adapter, and the cluster adapter's built-in MAC address is not used. Because of this, host to host communication (other than Network Load Balancing heartbeat-related traffic) is not possible on the cluster adapter.
The following characteristics apply:

• Adapters used as cluster adapters
  
  • The cluster IP address resolves to the adapter's cluster MAC address (which Network Load Balancing automatically generates).
  • If the cluster adapter's dedicated IP address is used, this IP address also resolves to the cluster MAC address.
  • The cluster adapter handles client-to-cluster traffic using the virtual IP address. However host-to-host traffic within the same cluster is not possible on this adapter because the MAC address for each host in a particular cluster is the same. For more information, see Address Resolution Protocol (ARP).
• Adapter used as the management adapter
  
  • Network Load Balancing in not bound to this adapter.
  • This adapter's IP address resolves to the adapter's built-in MAC address.
  • This adapter handles network traffic specific to the computer, including traffic from both inside and outside the subnet in which the computer is located.

Multiple network adapters in multicast mode

In multicast mode, the cluster's MAC address is assigned to network adapters that are functioning as cluster adapters, but the cluster adapters' built-in address is retained so that both addresses are used, the first for client-to-cluster traffic and the second for network traffic specific to the computer.
This following characteristics apply:

• Adapters used as cluster adapters
  
  • The cluster IP address resolves to the adapter's cluster MAC address (which Network Load Balancing automatically generates).
  • If the cluster adapter's dedicated IP address is used, this IP address resolves to the adapter's original, built-in MAC address.
  • In multicast mode, the cluster adapters can handle both client-to-cluster traffic and traffic specific to the computer, including all traffic from both inside and outside the subnet in which the computer is located.
• Adapter used as the management adapter
  
  
  • Network Load Balancing in not bound to this adapter.
  • This adapter's IP address resolves to the adapter's built-in MAC address.
  • This adapter can be used to handle the network traffic specific to the computer, including traffic from both inside and outside the subnet in which the computer is located.

Important

• Network Load Balancing does not support a mixed unicast/multicast environment within a single cluster. Within each cluster, all network adapters in that cluster must be either multicast or unicast; otherwise, the cluster will not function properly.
  However, there is no restriction on the number of network adapters: Different hosts can have a different number of adapters.

Network Load Balancing handles the resolution of the cluster's IP address to its associated multicast cluster media access control address within the Address Resolution Protocol (ARP) on your router. In rare cases, the use of a multicast MAC address might not be supported by the ARP implementation on a given router. If this problem arises, the cluster will not be accessible from outside the local subnet. To correct this problem, you must create a static ARP entry within the router. Refer to the documentation for your router to determine how to create a static ARP entry. For more information, see Using a router in Network Load Balancing system requirements.
If you disable multicast support (causing the host to revert to unicast mode), Network Load Balancing automatically instructs the driver belonging to the cluster adapter to override the adapter's unique, built-in network address and to change its media access control address to the cluster's media access control address. This is the address used on all cluster hosts. You do not need to manually configure the network adapter to recognize this address. (Note that some network adapters do not support changing their media access control addresses. If you experience this problem, you must install a network adapter that does.)
Notes

• Multicast support is not enabled by default. To enable it, see Enable multicast support. However, even if you do not enable multicast support, you are advised to consider using at least two network adapters (with one network adapter dedicated to handling client-to-cluster traffic) in order to achieve optimum performance and the full range of networking functionality. For more information, see Optimizing network performance.
  
• If you are using single network adapter, see Single network adapter and Single network adapter limitations.

==================
Optimizing network performance

If the cluster hosts are directly connected to a hub in order to receive client requests, incoming client traffic is automatically sent to all ports.
To limit switch port flooding (for example, when computers outside the cluster also share the hub), see Limit switch port flooding. The steps outlined make all incoming client traffic flow through one switch port and thereby conserve switch bandwidth. In this configuration, you are advised to consider adding a second, dedicated network adapter for each host connected to an individual switch port. The use of two network adapters per host on the cluster subnet helps to direct network traffic through the cluster hosts. Incoming client traffic flows through the hub for simultaneous delivery to all hosts, while outgoing traffic flows directly to the switch ports. Be sure to enter a gateway IP address in the Internet Protocol (TCP/IP) Properties dialog box in Network Connections for the dedicated network adapter, to cause outgoing network traffic to flow through that network adapter. At the same time, be sure to remove the default gateway for the cluster adapter, if one has been configured. It is essential that the default gateway be configured for either the cluster adapter or the dedicated adapter but not both.