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I've got an old Cisco WRT54GS router that I'm wanting to use to create a "experimenting" network. [ I want to packet sniff my 3DS, basically ]. My desktop has a wireless card that I use to connect to my actual internet connection from another router. Basically, I'm wanting a network set up like this:

3DS -> [ Old Cisco Router / Testing WiFi ] -> Desktop -> [Connected Router / Normal WiFi] -> Internet

My desktop is running Windows 8.1, and the connected router is a WD MyNet N750. I'm willing to put custom firmware on the Cisco router if needed, but if it can be achieved with the stock firmware I would just assume use that as it is one less headache.

Also if you know of a way to sniff packets from my 3DS on Windows, that would be awesome too. ( The reason I don't think I can as-is is something to do with NDIS 5 vs NDIS 6 - I'm not an expert with networks, I just write python code that uses sockets sometimes - but the answer that led me to believe I can't sniff w/o an OS change at least was here Wireshark - Help seeing all network traffic )

In short: My solution to being able to packet sniff my 3DS is to create a wireless network that runs through my desktop. I've tried this, but I'm not doing it right. If you know a better way to sniff the packets, OR if you know how to properly set up the wireless network I would appreciate it. (:

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  • Does your desktop have two Ethernet ports? Also, you don't mean "just assume" (you don't mean "just as soon" either, you mean "rather").
    – David Schwartz
    Oct 21, 2014 at 22:42
  • My desktop has a single ethernet port, and I'll have to remember that for next time, haha!
    – Full Metal
    Oct 21, 2014 at 23:37

1 Answer 1

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  • Install second network adapter on your desktop. This can be a USB-to-Ethernet adapter. Make sure drivers are properly installed and the second NIC shows up in ncpa.cpl

  • I am unsure if Windows 8.1 retains the Windows 7 behavior of using 192.168.137.X/24 for its subnet. If by some slim chance your "Normal Wifi" is using that range, change it.

  • Enable Internet Connection Sharing on the desktop. You want to share your Normal Wifi through your second Wifi.

  • On the testing Wifi, disable DHCP and routing. Your desktop will be doing both of those functions, you want it to be a dumb wireless bridge. DD-WRT allows you to disable DHCP and routing, flash it to DD-WRT if needed.

  • Configure the testing Wifi's WPA/WPA2 encryption to work with the 3DS. You may also want to set the testing Wifi to a different channel than your normal Wifi if needed.

  • Connect Ethernet cable from second NIC to a LAN port on the testing Wifi, not the WAN port.

  • For simplicity, disable anything that can generate traffic on the testing Wifi itself, such as DNS, DNSMasq, NTP, etc.

  • Download and install Wireshark.

  • I've never used Wireshark with Windows ICS but you ought to be able to capture packets on the second NIC and view what is going back and forth to the 3DS.

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  • Thank you for the help! Can the second adapter be the one built into my motherboard? And in my tinkering, I did notice a .137 pop up at some point, is that what you mean? And the "normal wifi" distributes IP's in the 192.168.1.* range, so leaving it as 192.168.137.X/24 should be fine, right? I'll look up DD-WRT and see where that gets me if I can't get the stock firmware to work correctly. Perhaps the WAN vs LAN port is what was stopping me earlier. And yes, Wireshark can isolate which NIC it scans. Thank you for your help! I'll comment here if I need further guidance.
    – Full Metal
    Oct 21, 2014 at 23:43
  • Second adapter can be built in your motherboard, wherever, as long as Windows sees it. I was talking about in the unlikely event your current "normal Wifi" is set to work on 192.168.137.X (not X.X.X.137) that you could encounter conflicts (it's probably 192.168.0.X or 192.168.1.X, so don't worry).
    – LawrenceC
    Oct 22, 2014 at 3:24

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