Hi

I have 2 new servers with both having 2 NICs. 

They both are DHCP connected for Public Network and working well. Public Network is a 100Mbps link.

I now want to configure a backup network so when backups are done or live migrations its done via the 1GBps link.

I see people mention a gateway should be used but what gateway. The company I got the servers from only provides a gateway fro public network.

So here are the information

Server 1

NIC1 - Public - Internet

NIC2 - Backup Network

10.0.0.10

255.255.255.0

Server 2

NIC1 - Public - Internet

NIC2 - Backup Network

10.0.0.11

255.255.255.0

Now when I got to \\10.0.0.11\c$ from Server1. Then it connects fine and I can transfer files but it goes over the Public Network at 10MB/s and not the Backup Network at 100MB/s which is what I want. If I however disable the Public NIC and then try copying the file it works perfectly.

Not sure what I am doing wrong.

You should not have two NICs on the same network. If you have configured both NICs for DHCP and have them connected to the same network, Windows is only going to use one of the NICs. It takes some special configurations in certain situations to get two NICs to work on the same network. It is not a recommended practice.

If you want two different networks to be defined for two different uses, you need to define them differently.  For example, in what you showed above, you gave us a single address for each host. Host 1 has 10.0.0.10 with a network mask of 255.255.255.0.  You did not provide any information about the second NIC, but if it is assigned via DHCP, it most likely also has a 10.0.0.x address, but I'm not sure.  Never tried having two NICs on the same network for DHCP.  Windows might not assign anything because it doesn't like two NICs on the same network.

Anyway, to use the second NIC you would need to connect it to a different network that offers DHCP or define static IP addresses.  Then the application that you want to use that network as to be configured to use that network.  How that is done varies, but in many cases it might be a matter of using the IP address in the path.

So if you defined the second NICs on the 1 Gbps network to have 192.168.100.x addresses with 255.255.255.0 subnet masks, and then you copied to \\192.168.100.x\sharename, you would end up using the 1 Gbps network for the copy.

  Your heading is misleading. This is not a routing problem. The only routing which takes place is in the 10.0.0.0 subnet and you are not changing that at all. What you need to do is set up a separate network on its own IP subnet (as Tim explained), and machines on the new subnet will communicate with each other directly. The traffic on that network will not be routed anywhere and does not need (and should not have) a default gateway configured. You should only have one DG per machine, not one per interface (unless you have two gateway routers and want to play with failover).