Question

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Issue with Multiple Network Connections in Windows XP

By matt.fishbeck ·
Hello All.

I have an issue with multiple network connections under Windows XP Professional Service Pack 2. See below for the details;

Setup

1. I have a regular LAN connection to the company network

2. I have added a 'dial up' network connection and am using a Nokia handset as a data modem over USB

Scenario

After plugging in the USB cable to the modem I right click on the dial up connection via 'Network Connections' and click Connect. The modem happily connects.

The problem is that Windows then 'Defaults' and uses the dial up connection (the data modem) as the default connection.

Both network connections are listed as 'Connected' in there status when this occurs but it would seem that when ever I connect to the data modem that windows diverts all TCP/IP traffic to the secondary connection. The regular connection with the LAN adapter seems to be halted, but is still listed as connected.

This same 'switching' behavior also occurs when I attempt to run simultaneous FTP sessions with FileZilla. I start one FTP download via one connection and attempt to start another running another instance of Filezilla. The second FTP download starts but the first one is halted. Again, under the network connection both com ports are defined as 'Connected'. I can seem to have one but not the other.

Question

Is there a way to simultaneously use multiple network connections in windows? Why does windows seem to switch to the last connection established? Any help would be greatly appreciated.

Matt

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All Answers

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How many 13 amp plugs fit into one 13 amp socket ? ...

by OldER Mycroft In reply to Issue with Multiple Netwo ...

That is the same question as you are trying to find an answer to. Strictly speaking only one plug can fit into one socket, unless you use an adapter.

However, sometimes the second 'plug' turns out to be a 15 amp, with round pins, then the troubles begin. Remove the 13 amp socket and replace it with a 15 amp round socket, but then the 13 amp square-pin plug won't fit.

They're BOTH plugs but they won't both fit simultaneously.

What you are attempting to do is the same.

The CPU must have a predefined path via which to send the data - it cannot figure out where the data should go if you offer it too many options, so it opts for the most recent option.

Similarly most users would be ecstatic to get ONE FTP working, yet you are trying to run two simultaneously?

By the same token, you cannot run a LAN connection and a WIRELESS connection simultaneously, because of the data path conflict, unless you employ 'bridging' techniques.

I've never heard of a bridging technique for what you are trying to do.

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Solution!

by matt.fishbeck In reply to How many 13 amp plugs fit ...

Hello guys,

Thanks for your colorful replies! :-) I enjoyed reading them.

What I am trying to achieve is related to testing involving multiple device contexts without giving too much away.

I appreciate your point concerning 13 amp plugs and 13 amp sockets. I physical plug will only sit in to one physical socket. But I solved this problem by using 2 13 amp plugs and 2 13 amp sockets.

I defined two dial up connections, cleared the routing table (route -f), and added two additional routes (route add <destination IP address e.g. FTP server> <one of the DUN ip address>), one pointing to an FTP server and the other pointing to a streaming video server. Both were happy to coexist with one physical handset.

Thanks again for your help!

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So you have managed

by Jacky Howe In reply to Solution!

to get two connections through the same phone line on one PC. What's the simultaneous
download speed like and the dual surfing experience. :)

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An extension of the problem

by rahul11 In reply to Solution!

Hi guys
I'm having exactly the same problem as Matt with some differences in the solution I'm hoping to arrive at. My office network blocks personal email sites, so I use a dial up data modem alongside the office LAN. Like Matt, I found that all data defaults to the dial up connection(and not the most recent connection as one post says). I've been trying to get one browser(firefox) working on the dial up for email and IE on the faster office connection for regular browsing. Matt, will your solution work for this? And in either case, can you dumb it down a bit and explain it?
Thanks!

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At a command prompt type

by Jacky Howe In reply to An extension of the probl ...
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Default Gateway

by Churdoo In reply to Issue with Multiple Netwo ...

What Mycroft is trying to say, so eloquently (please excuse my ignorance, but is a 13-amp plug a UK thing?), is that the new connection modifies your routing tables and adds itself as your new default gateway. Default gateway by definition is the next hop router used for communicating beyond your local network. With your default gateway on the second or newest connection, all externally bound traffic will route through this interface. Windows knows no way to balance multiple default gateways.

I'm not sure what you're trying to gain by leveraging multiple connections, but if you're trying to get a higher aggregate bandwidth, then I daresay that the benefit gained by trying to add the limited bandwidth of a cellular modem connection is not worth the work required to do so.

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I prefer the story about the 13 amp plugs :^0 ...

by OldER Mycroft In reply to Default Gateway

Yes - mains AC current in the UK is serviced by use of 3-Pin 13 amp plugs.

Back in the 70s the domestic UK ring-mains circuit was based on 3-Pin 15 amp plugs, but were superseded by the 13 amp variety because these PLUGS were fused.

On the 15 amp circuit when ANY appliance overloaded, it blew one of the B-I-G fuses you Americans are so fond of - the ones you keep hidden in your basements.

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Indeed, I enjoyed the story myself

by Churdoo In reply to I prefer the story about ...

and found it quite appropriate. Although admittedly I was a little confused when you started talking about square pins and round holes or vice-versa, but then a shiny object appeared out of the corner of my ... umm ... what was I saying?

Oh and thanks for following up with the lesson, and Greetings! from this side of the pond.

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