Connect two devices directly with twisted ethernet cable without disconnecting from wifi?

Question

I have a WiFi network at home with various devices connected which is reasonably reliable and gets me transfer speeds of about 4.5 MB/sec. However I often need to transfer several multi-gig files between my desktop and my laptop, both running Windows 7 64-bit, and for this I have a cat 5e crossover cable as both devices have gigabit ethernet adapters and my router is only 100 mbit.

If I disconnect WiFi on both devices I can get a fairly stable direct cable connection with transfer speeds of about 40 MB/sec (I guess this is about a third of gigabit, but I can live with that, its probably my laptop HDD write speed thats the bottleneck anyway, I haven't checked the spec...). If I disconnect WiFi on the laptop I can bridge the ethernet and WiFi connections on the desktop so both continue to have internet access, the transfer speed is still OK some of the time, but the connection becomes very unstable. I once tried disabling WiFi on the desktop but leaving it on on the laptop and actually got lower transfer speeds than I was getting over WiFi and the connection was even more unstable.

Does anybody know what on earth is the problem? Surely I should be able to leave WiFi connected on both devices, forget the network bridge (or bridge at both ends?), and get the file transfer to run down the physical connection when I want it to?

Answer 1

The thing that defines whether a network interface is internet connected or not is its default gateway.

The best approach from what I can gather from the description is to use a different IP network for the wired network, separate from what you use for normal network access. So lets say your router or dhcp server is handing out addresses in the 10.1.1.0/24 range, you would choose a different network for the wired connections and do not set a default gateway on the wired network cards.

So lets choose 10.99.1.1 255.255.255.0 for the desktop and 10.99.1.2 255.255.255.0 for the laptop. Go into the properties of the wired interface, into TCPIPv4 settings, set the IP address to manual and enter these details. Leave the wifi interfaces as normal.

Now if you want fast access between these two, you access them from each other by their IP address, not name.

Any traffic for the internet will ignore this network, and use the wifi interface (because it has a default gateway).

Again, do not put anything in the default gateway of the wired connections, and use a different network range than the one use for general purposes.