ISDN Issue

From the perspective of using 4 diffrent ISDN BRI's and devices to dial a single Centeralized BRI and ISDN device, this is no big deal, just create ppp users for each of the devices and create a dial string for each device, on the centeral device, then up to 2 remotes can be connected via a 64KB on a 2b+d BRI circuit.

If you are trying to have 4 seprate devices share the same Physical BRI circuit, like daisy chained together similar to the analog lines at a home, to my knowlegede this can't be done, due to the NT-1. The only solution here would be a physical line swap between devices. Be warned this will cause problems, like the circuit will hang and you will constantly be calling your LEC to open trouble tickets because your circuit is hung or is rejecting the SPID's.

hope this helped.

Attaching multiple ISDN modems to the same BRI line, or switching between modems on the same line will be truly ugly. Unlike a telephone modem, which is not connected when you are not using it, an ISDN modem is continuously talking to the central office equipment. If you were to throw a switch and move the line to a different modem with the same setup, there would be a loss of synchronization, and the new modem would take time to handshake with the line.

Think about switching the serial output of a single modem between four computers. There are devices available which will do this, the simplest being a 4-way serial switch. There is also modem sharing software which will do this.

Good luck.