Network connections dropping since adding a Sorenson VRS

I setup a home network for someone and it was fine with 2 machines.  Their modem stopped working and Comcast gave them a new one.  At the same time, I have since added a few more machines and a Sorenson VRS into the mix they are having problems when more than 2 machines are on the network at the same time.  The Sorenson is a video relay service which allows deaf people to communicate via video.  The Sorenson equipment came with the Dlink Router and specified that I add into the DMZ.  I tried setting this up without the Dlink Router but then the Sorenson wasn't working.  All the machines have been scanned for virus and have the latest security patches.  Both routers have the latest firmware.

Here is the setup.  The cable modem is plugged into the Dlink Router.  Off the Dlink Router I have plugged in the Sorenson VRS, a Dell Laptop, and the Linksys Router.  Off the Linksys Router, I have plugged in 2 desktops and there are 2 laptops that connect to this router via a wireless connection.

Cable modem -> Dlink Router -> Sorenson VRS
                                             -> Dell Laptop
                                             -> Linksys         -> Dell Desktop            
                                                                     -> Dell Desktop
                                                                          wireless (Dell Laptop)
                                                                          wireless (Thinkpad)

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Rob WilliamsCommented:
Does the Dell laptop that is plugged into the D-link continue to work OK?

How have you wired the Linksys? There are 2 options:
1) a cable from a LAN port of the D-Link to the WAN port of the Linksys
2) a cable from a LAN port of the D-Link to a LAN port of the Linksys, making it an access port.

If you went with option 1 it should work but it can cause problems with a few services or possibly un-expected results from time to time. If so, try option 2. With option 2 connect as suggested, give the Linksys a LAN IP in the subnet/range as the D-Link and make sure it doesn't conflict with the DHCP range of the D-Link. Then disable DHCP on the Linksys, and leave the WAN configuration of the Linksys blank. This eliminates 1 "hop" and double NATing (Network Address Translation), gives you a single DHCP server -the D-Link, and maintains the wireless functionality.

Another option might be the Sorenson unit using most of the bandwidth. Try disabling it to isolate if the new network configuration is the problem or the Sorenson.

Just a few suggestions to try.

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skates94Author Commented:
Unfortunately, I don't know which machines aren't connecting as I haven't been there when they have had problems.  The Dell Laptop plugged into the D-LINK router is really only used when the Sorenson VRS is in use.  

I have the cable going to the the LAN port of the Linksys.  The D-Link IP address is and the Linksys IP address is  I'm heading over there this afternoon and will try your suggestions.  Thank you for your reply.
Rob WilliamsCommented:
Sounds like the Linksys is set up correctly so that is not likely the problem. May be difficult to diagnose where it sounds like it is not a consistent problem and you are not always on site. Good luck, I will be curious as to how you make out.
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Rob WilliamsCommented:
Might want to try a bandwidth test just to see how it 'stacks up' against other locations. If low, as suggested, the Sorensen might be taking full control. If that were the case you would normally go to a router that offers QOS (Quality of Service) where you can impose bandwidth restrictions. However sounds like you are required to use the D-Link.
The VRS might be taking up too much bandwidth. How well do things work when you're NOT using the Sorenson (we're assuming that it's off at that time)? In addition, how often does that unit get used?

Also, you probably want to set up the Linksys as an access point (no DHCP or NAT) rather than as a normal router. It's already been mentioned to use a QoS router.

Does Comcast offer higher speed service in that area (some places you get an additional 2Mbps for some additional fee)? It might alleviate SOME of your problem, but bandwidth control is going to be the key thing to fixing your problem.

What model routers are you using?
skates94Author Commented:
The Sorenson is primarly used on weekends, the child that uses it goes to boarding school during the week.  They have been having problems during the week when the unit is not on.  From what I have read about Sorenson VRS, I have to use the D-Link Router.

The D-Link is modle DI-604 and the Linksys is WRT54G V 1.1

Try this: Take the D-Link and Sorenson out of the equation for a few days... a stretch when you know that its user isn't around. The D-Link router might be causing you some headaches. If that's the case, you might need to replace that router... or you might need to tweak some settings on it.
skates94Author Commented:
Thank you everyone.  I disabled the dhcp from the Linksys and {knock on wood} it's working.  This was even with the Sorenson running.
Rob WilliamsCommented:
Thanks skates94,
Thanks for the update.
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