Skip to main content

windows - Which network connection is used if connect using multiple interfaces


I'm using Windows 7. I connect to the internet using both my Ethernet port and Wifi.


How can I know which interface is Windows using to connect to the internet? What if there are even more interfaces, like an additional USB Wifi adapters? Is there a general rule for this?



Answer



There are two things you need to look at:



  1. The routing table (and its default interface).

  2. The preferred network settings in windows.


The routing tables are easy. Start a shell and (e.g. start run cmd.exe) and use the command route print. One of the entries will have network destination 0.0.0.0 (that means every destination not explicitly listed). The IP in the column Interface is the IP belonging to the card use to reach the default interface.



IPv4 Route Table
======================================================================
Active Routes:
Network Destination  Netmask     Gateway        Interface      Metric
      0.0.0.0        0.0.0.0    192.168.1.252   192.168.1.12     20

I know this is a bit brief, but there is a nice long answer at in this post on our sister site.


That part is rather generic and works that way for every computer, regardless if it is running windows, CPM, DOS, Linux, BSD, OS X, etc etc.



The second point is windows specific.


Windows defaults to the link with the highest speed.


If you have wireless up to 54Mbit and wire (usually 100mbit or 1000mbit) then windows will use the wired card if it is plugged in, and fall back to the wireless card if it is not plugged it. (This is not always a case of wired over wireless, you can have a 100mbit wired connection and a 300mbit wireless connection).


This might even change when you are waling around with the laptop, or when someone moves between your laptop and the WAP. (Water, and thus human are great absorbers of 2.4 GHz radiation.). Thus the actual used connection can change at any time.


If desired you can manually select which network should be use by going to the local area connection settings under Adapters and bindings.



Edit to answer some of the questions on comments which got to long to answer without using several 'comment posts':



Can you say that the interface with the lowest metric in the route table is the one that is used? – awe



Yes.


If there is more than one path then windows will look first at the most specific path and use that. If there are multiple paths to the same destination then it will use the path with the lowest metric value.


This value may be manually set to indicate cost (as in €/MB), or the number of routers to cross (more a technical cost), or speed.


This post on Serverfault describes how windows sets the default values for the metric.


Other interesting posts are:



  1. Technet: The IP routing table

  2. Technet: The route command

  3. Here on [SU]: How does windows 7 decide which route to take if there are 2 connections



Update for windows 8.1 (with thanks to Joseph Quinsey):


For Windows 8.1, to find the manual selection, you need:



  • Network and Sharing Center

  • Change adapter settings

  • Press Alt

  • Advanced

  • Advanced Settings

  • Adapters and Bindings,


or



  • right-click Start

  • Network Connections

  • Press Alt,

  • Advanced

  • Advanced Settings

  • Adapters and Bindings,


Comments

Post a Comment

Popular Posts

Use Google instead of Bing with Windows 10 search

I want to use Google Chrome and Google search instead of Bing when I search in Windows 10. Google Chrome is launched when I click on web, but it's Bing search. (My default search engine on Google and Edge is http://www.google.com ) I haven't found how to configure that. Someone can help me ? Answer There is no way to change the default in Cortana itself but you can redirect it in Chrome. You said that it opens the results in the Chrome browser but it used Bing search right? There's a Chrome extension now that will redirect Bing to Google, DuckDuckGo, or Yahoo , whichever you prefer. More information on that in the second link.
Post a Comment
Read more

linux - Using an index to make grep faster?

I find myself grepping the same codebase over and over. While it works great, each command takes about 10 seconds, so I am thinking about ways to make it faster. So can grep use some sort of index? I understand an index probably won't help for complicated regexps, but I use mostly very simple patters. Does an indexer exist for this case? EDIT: I know about ctags and the like, but I would like to do full-text search. Answer what about cscope , does this match your shoes? Allows searching code for: all references to a symbol global definitions functions called by a function functions calling a function text string regular expression pattern a file files including a file
Post a Comment
Read more

How do I transmit a single hexadecimal value serial data in PuTTY using an Alt code?

I am trying to sent a specific hexadecimal value across a serial COM port using PuTTY. Specifically, I want to send the hex codes 9C, B6, FC, and 8B. I have looked up the Alt codes for these and they are 156, 182, 252, and 139 respectively. However, whenever I input the Alt codes, a preceding hex value of C2 is sent before 9C, B6, and 8B so the values that are sent are C2 9C, C2 B6, and C2 8B. The value for FC is changed to C3 FC. Why are these values being placed before the hex value and why is FC being changed altogether? To me, it seems like there is a problem internally converting the Alt code to hex. Is there a way to directly input hex values without using Alt codes in PuTTY? Answer What you're seeing is just ordinary text character set conversion. As far as PuTTY is concerned, you are typing (and reading) text , not raw binary data, therefore it has to convert the text to bytes in whatever configured character set before sending it over the wire. In other words, when y
Post a Comment
Read more

networking - Windows 10, can ping other PC but cannot access shared folders! What gives?

I have a computer running Windows 7 that shares a Git repo on drive D. Let's call this PC " win7 ". This repo is the origin of a project that we push to and pull from. The network is a wireless network. One PC on this network is running on Windows 10. Let's call this PC " win10 ". Win10 can ping every other PC on the network including win7 . Win7 can ping win10 . Win7 can access all shared files on win10 . Neither of the PCs have passwords. Problem : Win10 cannot access any shared files on win7 , not from Explorer, nor from Git Bash or any other Git management system (E-Git on Eclipse or Visual Studio). So, win10 cannot pull/push. Every other PC on the network can access win7 shared files and push/pull to/from the shared Git origin. What's wrong with Windows 10? I have tried these: Control Panel\All Control Panel Items\Network and Sharing Center\Advanced sharing settings\ File sharing is on, Discovery is on, Password protected sharing is off Adapte
Post a Comment
Read more