BACK TO BACK ISDN

[cbertron]

Has anyone ever made a cable to connect to ISDN routers together via a direct connection?

 

[aceman]

I am unclear how the protocol will operate and the numbers be processed with just a back to back cable ?<br><br>Whilst the pin outs can be arranged so as to allow TX/RX and TIP/No Connection to be crossed there will be no way of processing the SAPI and TEI ?<br><br>On a serial back to back connection I have simply used a DTC and a DTE cable connected with clock source applied to the DTC interface. <br><br>If anyone knows how to simulate ISDN back to back on Cisco's without purchasing something I would also be interested.<br><br>Not much help Cbertron.

 

[Lazarus777]

I concur, there is no way possible to connect two ISDN devices this way. It would be as ridiculous as plugging a crossover cable between two telephones: no talk battery and there's no switch between the routers...no network. You'd have clocking issues as well...

Most likely your Cisco BRI router will not allow you to set up your serial ports to cascade them but that's about your only option. Either that or drop BRI from your PBX.

I realize that is even less help but I hate to see you waste time on this.

Lazarus

 

[MaxPipeline]

I concur with others. Yes you can theoretically crossover TX/RX but without D-channel signalling, call setup cannot take place. Most likely whatever router you have would not be able to generate the D-channel signal. Therefore you cannot back-to-back ISDN.

 

[cticstinst]

what is the difference between an isdn bri u interface and an s/t interface, and how are they used. also what is a nt1 device. we are new to the isdn field.

 

[CinemaPhones]

ISDN U interface is the U.S. standard for BRI lines. In other parts of the world, Telco's deliver an S/T interface. In short, the U interface is a 2 wire circuit which must be converted to a 4 wire NT2 circuit. The device that does this is a NT1. Nearly all U.S. equipment routers, modems, pbx line cards have this NT1 device built directly into the circuitry. This allows you to plug equipment in a single piece of equipment and go.

The NT2 (s/t) interface alows more than one device to be connected. Theroretically with SPIDs, you could connect up to eight or more devices to one ISDN line all with different numbers and appearances (depending on the central office's switch). In the U.S. it is unlikely your central office will EVER provision your line with more than 2 SPIDS.

The primary use of s/t type equipment in the U.S. is behind PBX phone equipment which supports 2B data and video conferencing equipment.

 

[voipguy254]

It is absolutley possible to connect 2 ISDN VWIC on a cisco router together via a cross over cable and make calls from one to the other. The config is quite simple infact:

The interface that you want to use to emulate the telco would look something like this:

interface Serial1/0:23
no ip address
no logging event link-status
isdn switch-type primary-net5
isdn protocol-emulate network
isdn incoming-voice modem
no cdp enable

The interface making the call would look like this:

interface Serial1/1:23
no ip address
no logging event link-status
isdn switch-type primary-net5
isdn incoming-voice voice
no cdp enable

dont forget to set (in this case) the clock for 1/0 to internal.

all that needs to be done after this is to make your dial-peers, which I assume you know how to do.

cheers.

al.