Ever wonder what happens when you connect BOTH via wireless and wired ethernet to the same router? Probably not, but it's still a good question. Which interface gets priority? Where does the traffic go? How does it work? Is it safe to leave both connected?
I had a handy laptop (that belongs to a customer) with a fresh install of XP SP2, so I thought I would see how it works.
IPCONFIG
| Ethernet adapter Wireless Network Connection 2: | Connection-specific DNS Suffix . : | IP Address. . . . . . . . . . . . : 192.168.1.102 | Subnet Mask . . . . . . . . . . . : 255.255.255.0 | Default Gateway . . . . . . . . . : 192.168.1.1 | | Ethernet adapter Local Area Connection: | Connection-specific DNS Suffix . : | IP Address. . . . . . . . . . . . : 192.168.1.105 | Subnet Mask . . . . . . . . . . . : 255.255.255.0 | Default Gateway . . . . . . . . . : 192.168.1.1
OK, that looks normal. Each interface gets a seperate IP address. Both interfaces are active and enabled.
ROUTE PRINT
| =========================================================================== | Interface List | 0x1 ........................... MS TCP Loopback interface | 0x2 ...00 14 a5 18 56 71 ...... Broadcom 802.11b/g WLAN - Packet Scheduler Miniport | 0x3 ...00 0a e4 d8 2c 38 ...... Realtek RTL8139/810x Family Fast Ethernet NIC
- Packet Scheduler Miniport | ========================================================================== | | Active Routes: | Network Destination Netmask Gateway Interface Metric | 0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.102 30 | 0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.105 20 | 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 | 192.168.1.0 255.255.255.0 192.168.1.102 192.168.1.102 30 | 192.168.1.0 255.255.255.0 192.168.1.105 192.168.1.105 20 | 192.168.1.102 255.255.255.255 127.0.0.1 127.0.0.1 30 | 192.168.1.105 255.255.255.255 127.0.0.1 127.0.0.1 20 | 192.168.1.255 255.255.255.255 192.168.1.102 192.168.1.102 30 | 192.168.1.255 255.255.255.255 192.168.1.105 192.168.1.105 20 | 224.0.0.0 240.0.0.0 192.168.1.102 192.168.1.102 30 | 224.0.0.0 240.0.0.0 192.168.1.105 192.168.1.105 20 | 255.255.255.255 255.255.255.255 192.168.1.102 192.168.1.102 1 | 255.255.255.255 255.255.255.255 192.168.1.105 192.168.1.105 1 | Default Gateway: 192.168.1.1 | =========================================================================== | Persistent Routes: | None
Note the value for Metric for each interace. The wireless at .102 has a higher "cost" of 30 than the ethernet connection at .105 which has a cost of only 20. That means that all the traffic will go via the lower cost ethernet route. Checking the bytes moved on the network device status pages confirms this as all the traffic is going via ethernet. Nice.
Unfortunately, my BEFW11s4 v4 isn't too smart about multiple connections from the same computer. All it knows is that each IP address is probably a different computer. When I start a download with both the wired and wireless connected, the download goes via the wired. If I then pull the plug on the ethernet during the download, the wireless sorta takes over, but the download just stops. The router is not smart enough to move the traffic to the wireless interface. Bummer.
Therefore, it's safe to leave both wired and wireless connected. As long as the routing table shows a different metric for the two interfaces, the traffic will go via the fastest route. Some laptops (i.e. Toshiba Config-Free) have a utility that will switch interfaces on and off, but that appears to be un-necessary.