One of the few frustrations with the Jetpacks is the lack of ethernet ports. I've just obtained the 6620L to serve as my primary source of home Internet, replacing a network based on an Airport Extreme base station. But my home phone consists of Google Voice via an Obii 100 device, which requires an ethernet connection.
I first tried extending the network with Airport Extreme, but the device doesn't have that capability. However some models of Airport Express are able to extend a non-Apple network, and each has an ethernet port. I have an Airport Extreme model A1264, so I tried it and within a couple of minutes have both an extended network and a working voip phone. According to a poster to Apple's user forum, the A1392 or A1264 versions of the Express with accomplish this, but the A1084 and A1088 will not. (A1392 is the current production model.)
I suppose that it is possible for PC users to accomplish the same, but I cannot test that. I also do not know if an ethernet hub can be attached to the single port on the Express.
Jetpacks are wireless and USB tethering devices only. If you need an Ethernet cable for one of your personal devices then you will need to get a wireless bridge setup and configured to provide that functionality. Wireless bridges connect to other wireless access points and then provide an cabled Ethernet connection for any additional devices. Many home routers can be converted into a wireless bridge if the hardware contains the correct antenna and software to support it.
If you cannot find a way to convert your airport into a wireless bridge then you will need to purchase a new device that can support that network functionality.
I don't understand the point of your reply. I explained for those interested how an Apple Airport Express can be used to extend Jetpack wifi and make a useful ethernet port available.
A correction to my initial post:
I referred to Airport Extreme model A1264, but I meant Airport Express. As I said, Airport Extreme won't work.
The easiest solution would be to get a WIFI as WAN router. In short they capture a wifi signal and re-broadcast it, or they can be configure as a wifi bridge, allowing you to use the ethernet ports and extend the WIFI coverage area
I would recommend the following:
Not sure why that is easier, but for many people there is an obvious advantage in using an Apple product that coordinates with other devices they already use, such as Apple TV and iPhones. Apple's video and audio streaming are famously easy. It took me about 3 mins. to configure Airport Express so it would work with Jetpack, and seconds to plug my voip device into the router's ethernet port. Airport Express has a wireless USB printing and an optical/analog audio jack. The prior generation Express. with all those same features, can be had for $50. Many people already have an Express they may not be using.