Can I set a static network route for outbound socket in NODE.js?

Question

I have three network cards in my server where VMware is "owning" one subnet of 192.168.114.0 and a gateway at 192.168.114.1.

I have a "Logger" application running on the host (10.x.x.x) NIC and a third NIC that is for outbound traffic of 172.x.x.x which is not really relevant here.

My Node.js server is listening to 192.168.114.1 running on the server where the primary NIC is 10.x.x.x. In VMware there are other servers running all with IP's in the range of 192.168.114.x.

There are also databases installed on 10.x.x.x which the VMware servers are accessing without a problem.

The servers in VMware finds the Node.js server fine (TCP SYN sent) but then Node.js sends all TCP packages out on 10.x.x.x interface and thus I don't get anything back to the VMware server.

Adding a static route to Windows doesn't solve the problem as Node.js still selects the lowest metric which is always the primary NIC it seems.

As a test I added a new VMware server using a 10.x.x.x address and then Node.js sends the packets correctly. I also tested to set the primary NIC to a 192.168.114.x address and that too makes it work so it is clearly a routing issue.

Question being, how can I get Node.js to route out to a selected NIC rather than the primary one?

Answer 1

It depends on what you're doing.

For net.Server or http/https.Server you can pass the interface's IP to the server instance's listen() as the second argument.

For net.connect()/net.Socket.connect() or http/https.request() you can pass a localAddress option that contains the IP of the interface you want to use.