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share comcast cable modem with a VPN connection at home

Posted on 2004-09-21
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Last Modified: 2013-12-14
i already have a comcast cable modem at home that connects thru a VPN box then to the PC that used as work purpose to connect to the remote company network(work from home).
i am thinking to build up another PC for my kid, so my questions here are:
1. is the VPN box( supplied from the current employer) only dedicated to the employer's network? if i connect 2nd PC to it will all traffic from the 2nd PC also go thru the employer's network? i don't like this. i just want the second PC connected to the internet as regular at-home computers, is there any way to use the same VPN box but not thru private network? the cable modem has only one cable out to the VPN.
2. the first PC is win2000 pro, is there any requirement for 2nd PC OS?
3. do i need a hub or router if i cannot go thru VPN for the reasons above, and if so, is there any problem to the first computer to put the hub/router in between the modem and the VPN? will it still see everything as usual or i need to change some settings?
comcast cable modem can allow up to five PC connected at the same connection.
thanks.
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Question by:wangzq
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by:Yan_west
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Usually, A vpn BOX is used to create a tunnel between 2 locations. If the Access list at your employer's site allows all your network to get in, then Yes, your kid's computer will have access to the other network.

There is no requirement for the second OS btw.. but I would definitly go with XP for your kid :).. more stable, and easier to understand.

If your network is connected via a tunnel. Then you will have to ask your system administrator at the other site to create a rule that is only accepting traffic from the IP address of your PC, and reject the rest.
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by:Yan_west
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btw, even if you would put a linksys box on your side, plugged in your vpn box, it would allow access anyways... everything in your network, no matter what will have access... like I said.. your sysadmin has to create a rule..
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by:wangzq
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i am not clear by your answer.
looks like there are some 'if's. i need to be sure the way will work. as i said, the kid's PC will not want to bother sysadmin to create any new rules. so my point is how to connect the PC so it will not interfere the VPN, and will not get into the VPN  first then to access internet, because otherwise the company's filtering and firewall will also apply, which is not what i want.
 the linksys you mean hub or router?the vpn box is after the modem, so i figured it should be possible to add a relay in between, without adding any on the software side, just like the electrical circuit?

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by:Yan_west
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Ok, your network should be like this:

Internet
    |
Modem
    |
VPN BOX
|        |
PC     PC

Is that right?

If that is so, and the tunnel goes up as soon as the box is up. you cannot split your connection between the modem and the vpn box.. I guess you could buy a cheap linksys internet router, and unplug the vpn box to go on the internet without being on vpn, and unplug the linksys and replug the vpn box when you need access to your corporate lan.. but that would be a bunch of trouble.

You could also ask your admin how to get in your box to disable the tunnel, and only re-enable it when you need..
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by:wangzq
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yes, it is like the picture, but is it possible to insert a hub in between the modem and the VPN box;, like this:

modem
    |
  hub--home PC
  |  
VPN
  |
work PC

i will also call comcast to see if they can help to answer the question.
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by:Yan_west
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Hmmmm, usually, your VPN Box has to be plugged in the modem directly..  it has to receive the ip address from the Internet provider directly.. if it'S plugged in the other Internet router, it will not work out..
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by:Yan_west
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It would be possible if you would have a real router instead of the hub.. but it would cost you alot to do it, because you would need to have a router with 3 interfaces, and put your home PC in a different subnet. It would also be pretty complicated to setup for simple home use..

Call them, but I'm 99% positive that they wont support this type of configuration..
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by:wangzq
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the words from comcast tech support:

i can directly connect kid's PC into VPN box, it does not necessarily mean that the kid's PC will go thru company's network before it sees the internet. VPN only add security to certain PC, itself is a built-in router/hub already. so the kid's PC should be able to use its hub/router part to see the internet , and not thru VPN part for work purpose.
also he said it is ok to insert another hub in between modem and VPN box to split the traffic, but it's pointless since VPN box can do that already.
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by:Yan_west
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Yes, it will have access to your Internet connection, but the kid WILL be able to connect to your corp lan if he tries to...
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by:Yan_west
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As I reread our discussion, I didnt see that you did not want your kid to pass through your company internet access..

I have a PIX 501 at home with a tunnel to our network, and My internet access is local.. :)
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by:Yan_west
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If you do that, be sure that your kids computer has update patches and AV definitions at all time..
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I still think that you cannot plug an internet router into a second internet router...

I just spoke with our engeneer, and he told me that for a VPN tunnel to work, each end of the tunnel must be on a public IP address.. if you put your VPN box behind your hub, your external interface will not have a Public IP address assigned..
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by:aj247
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1. Vpn box may be blocking ports.  If you're going to be gaming, may have to assign ports in the vpn box to allow out.
2. No requirement 2 PC OS.
3. a hub or router should work.  Make sure not between the modem and vpn.  Must be behind vpn - vpn to modem shouldn't have to change any settings.
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