Wireless AND ethernet to same router

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.

--
Jeff Liebermann jeffl@xxxxxxxxxxxxxxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.

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