Windows File Share not using Correct NIC Interface.

Question

Hi
I have Windows 2012 R2 server with two 1gb NICs.  I want to use NIC1 for the regular network traffic/Internet and the NIC2 for database traffic.  NIC1 has IP Addresses of 64.141.xxx.xxx (I am not showing the last 6 digits for security reasons)
and 192.168.10.21.  NIC2 has the IP Address of 192.168.11.2.
The Workstation accessing this server also has two NICS.  NIC1 has the IP address of 64.141.xxx.xxx and 192.168.10.22.  NIC2 has the IP Address of 192.168.11.4.
I created a share on the server myDataShare$.  On the Workstation I access the share using \\192.168.11.2\myDataShare$ and everything works accept that the data from the share is sent across NIC1 but I want it to go over NIC2.  If I add static
routes to both machines it makes no difference all network traffic always goes out on NIC1 for both machines.
If look at the status of each NIC on the send and receive bytes only NIC1 show any traffic.  NIC2 is silent.  How do I get traffic for the 192.168.11.0/24 subnet to use NIC2?
The strange thing is that if I ping a 192.168.11.0/24 address it goes over NIC2 but file sharing seems to ignore NIC2 altogether.
Thanks,
Simon

Answer 1

Hi Simon,
Windows Vista and later are based on the strong host model. In the strong host model, the host can only send packets on an interface if the interface is assigned the source
IP address of the packet being sent. Also the concept of a primary IP address does not exist.
If the program specifies a source IP address, that IP address is used as the source IP address for connections sourced from that socket and the adapter associated with that
source IP is used as the source interface. The route table is searched but only for routes that can be reached from that source interface.
You can try to set the “skipassource” flag ,by using this flag, the added new addresses are not used for outgoing packets unless explicitly set for use by outgoing packets.
The detail information about skipassource flag:
Source IP address selection on a Multi-Homed Windows Computer
http://blogs.technet.com/b/networking/archive/2009/04/25/source-ip-address-selection-on-a-multi-homed-windows-computer.aspx
The related KB:
How multiple adapters on the same network are expected to behave
https://support.microsoft.com/en-us/kb/175767/en-us
The related third party article:
Exchange 2013 on Windows Server 2012 with multiple IP addresses on a single NIC
http://blog.enowsoftware.com/solutions-engine/bid/185076/Exchange-2013-on-Windows-Server-2012-with-multiple-IP-addresses-on-a-single-NIC
I’m glad to be of help to you!
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