Concurrent Network Connections

Posted on 2006-11-14
Last Modified: 2013-12-14
Is it possible to have concurrent network connections?  I can directly connect to my school's network from home (I live at a boarding school), and thus have free internet access.  The problem is that the internet connection is painfully slow and a victim of our sysadmin's firewall and web filter.  So, as a solution I now have a cable internet connection.  Is it possible for me to use this connection for the internet (via USB) while remaining on the netowrk (vie ethernet) for e-mail and access to shared drives & servers?

I'm running a cutum WinXP Pro desktop with 1 GB RAM & a 3.2 MHZ CPU.

Thanks in advance!

Question by:zbrusko
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LVL 14

Expert Comment

ID: 17944869
nope, windows will only allow 1 network connection
however if both connections are live with separate netwk cards (usb & ethernet) then it is possible to bridge the connections, see here:

Expert Comment

ID: 17946128
What if one of the connections is "wired", and one is "wireless"...say the school network is wired and the cable is wireless (using separate cards as "FT" mentions above).  Can't you then just temporarily disable the one you don't want to use and let the other one be live?

I dunno...I'm just wondering?
LVL 20

Accepted Solution

ElrondCT earned 350 total points
ID: 17947757
I disagree with FriarTuk. You can have two network connections, not bridged. However, you then need to tell your computer which connection it should use for going to which sites. This is accomplished with routing assignments, using the ROUTE command at the command prompt. To do this, you need to know what IP addresses your school's network uses, and its default gateway. You can get the gateway information by typing IPCONFIG at the command prompt, while connected to the school's network. You'll get something like:

Ethernet adapter Local Area Connection:

        Connection-specific DNS Suffix  . :
        IP Address. . . . . . . . . . . . :
        Subnet Mask . . . . . . . . . . . :
        Default Gateway . . . . . . . . . :

Yours will be different; a school network is unlikely to start with 192. Most likely, you'll be connecting to a class 2 network, where the first two sets of IP numbers are the same for all computers on the school campus, and the last two sets can vary. If, for instance, the default gateway is, you'll want to give the command

route add mask

What this means is that any request to access an IP address that starts with 22.100 will go to the gateway at address

Next, you want to set up your two adapters so ordinary Internet traffic will go through the USB connection. Go to Control Panel, Network Connections. For each of your two adapters (USB and Ethernet), right click the adapter, choose Properties, select "Internet Protocol (TCP/IP)", choose Properties, choose Advanced (on the General tab), and uncheck Automatic metric. Set the metric for the USB to 1; set the Ethernet to 2. Now your computer will give preference to the USB connection. If it's unavailable or if you're using an IP address that's in the 22.100 range (or whatever your actual numbers are that you use in the route add command), then your computer will use the Ethernet connection.
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LVL 20

Expert Comment

ID: 17947950
Forgot to mention that you should put -p in the route add command, to make it persistent (i.e., be reinstated after a reboot). So it would be something like:

route -p add mask

You can get a list of route settings by giving the command

route print

More information on using route add is available at


Author Comment

ID: 17949780
When I run ipconfig, the default gateway is blank...

How do I proceed from there?

Is this something my sysadmin can give me?
LVL 20

Expert Comment

ID: 17949927
AFAIK, if the default gateway is blank, it means that you have no network connection on that adapter. Is the IP address for the adapter something starting with 169? If so, you need to repair the connection. (Control Panel, Network Connections, right-click on adapter, choose Repair.) I'd recommend disconnecting the cable modem while you're trying to get the school connection set up properly.

If this isn't sufficient to give you direction, post the results of the IPCONFIG command, and we can try to decipher it more.

Author Comment

ID: 17950022
I am running ipconfig from my office, which is connected to the network.  I am trying to run both at home, but in the meantime I thought I would get the info I needed from here.

My results are:

Ethernet Adapter Local Area Connection

     Connection-Specific DNS Suffix:
     IP Address:
     Subnet Mask:
     Default Gateway:

LVL 20

Expert Comment

ID: 17950496
Hmm, I'm surprised by that. Your sysadmin would probably be able to give you that information. I thought tracert (traceroute, which shows the steps to an IP destination) might show it, but as I test that here, it looks like it doesn't list the gateway, but immediately goes to the next step. One other thing to check, though, would be if you have a static IP address assigned; go to Properties of TCP/IP for the adapter as described above, and see if a gateway is assigned there. If so, take that address.

With your IP address, you'd want the route add command to be:

route -p add mask 10.x.y.z

where "x.y.z" would be the address for the gateway that you're actually using.
LVL 14

Expert Comment

ID: 17953724
according to El's ms$ link for routing it states this:
"Windows NT computers can be configured with multiple default gateways. When a dead gateway is detected by TCP, it can direct IP to switch default gateways to the next gateway in the backup list. This switch can occur when there are multiple gateways configured for the same network adapter or when different default gateway addresses are given on various network cards on a multihomed computer."

which means that when the default gateway doesn't connect it will switch to the other.  so how does this allow simultaneous connections to different networks, answer:  it doesn't.  you will only get one ip addr from one source, you will not get two ip addr's from two different sources at the same time.

solution would be to use your usb high spd connection, then vpn into the school's to accessing that netwk (this will require the school's sysadmin to setup vpn access).
LVL 20

Expert Comment

ID: 17956020
I have direct experience in setting up two network adapters with routing assignments for internal and external networks, in just the type of situation described here. It's been about three years since I last did it, so it's possible I've got a glitch or two in applying my old notes to the current situation, but it can be done more or less as I describe.

The structure I'm describing will use the Ethernet connection all the time for the school network. It will use the USB connection as the primary Internet connection, but if for some reason that fails, the computer will automatically roll over to the school's connection. This is not impossible.

Author Comment

ID: 17956158
I've checked for our default gateway from your net admin.  I will hopefully get a response and be able to get things going tonight.  Thank you for your comments, and I will hopefully have a verdict for you tomorrow.
LVL 20

Expert Comment

ID: 17956178
BTW, FriarTuk, it's not hard to see a computer with two network adapters get two IP addresses. Take a laptop with a (connected) wireless card and also plug it in by cable to a router.

If you look at the summary of MSKB article 159168, which I referenced, it says: "On multihomed computers connected to disjointed networks, static routes may be added to the routing table to get connectivity to remote networks." Note the term "disjointed." Oddly, the article is listed as applying to WinNT and 2000, but has never been updated to say it applies to XP. However, it does work with XP as well.
LVL 66

Expert Comment

ID: 17961263
I believe the term youare looking for zbrusko, is "MultiHomed"

Here is an EE PAQ that talks about this type of setup, being on multiple subnets at the same time....

Title: Multi-homed LAN

Tons of links in there to different resources on the topic.....
LVL 27

Expert Comment

ID: 17964835
I agree with Elrond.  I have my XP Pro Laptop on my corporate wired net 172. right now, and connected to a wireless test DSL line with a 192. address.

When I want to run my default route through my wired side, I click on an icon which executes this script:
'This is to allow inbound outbound

'delete the outside default route
route delete mask

'add the inside default route back in
route add mask

When I want to run my default route out the wireless dsl connection, I click on an icon which executes this script:
'This is to allow traffic outbound

'add a default route to the wireless
route add mask

'add an helpdesk route to internal
route -p add x.x.192.0 mask
'add private routes to internal
route -p add mask
route -p add mask
'add corporate route to internal
route -p add x.x.240.0 mask

'delete the inside default route
route delete mask


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