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T1 PRI and FXO PSTN Simulation??


I know we can have cross over cable to conect between MFT-T1s or E1s for PSTN simulation.

Is there any way to have FXO simulation?? Any documentations or ideas??



Cisco Employee

Re: T1 PRI and FXO PSTN Simulation??

for fxo simulation you need to connect fxo port to fxs port (straight through rj-11)

Re: T1 PRI and FXO PSTN Simulation??

Yes very much you can do that on any router (voice supported). I have 2600s back to back with a t1 cross over. All you need is a NM-HDV or NM-HDV2 (with or without onboard T1s) and DSPs on them, to make this happen. If you use ISRs then you may use DSPs on the motherboard and use HWIC slots to put the vwics.

You should set one end of the link to clock source line while set the other to clock source internal. Make the channels same on both ends and you are good to go. On the router that is on the PSTN side, your serial interface should be configured to emulate network side (user side is default).

int s1/0:23

isdn protocol-emulate network

With this setup you can simulate

T1 PRIs: using pri-group command (You need a T1 vwic or you can use a NM-HDV2 with one or two onboard T1/E1 ports. YOu can use the card type t1 command to set the ports on the NM to type T1)

E1 PRIs: using pri-group command (You need a E1 vwic or you can use a NM-HDV2 with one or two onboard T1/E1 ports. YOu can use the card type e1 command to set the ports on the NM to type E1)

You can additionally emulate T1 CAS (using ds0-group command) and also E1 R2.

For FXO simulation you need FXO port on one router and FXS on the PSTN side. Routing between various call legs can be done using POTS dial peers on the PSTN emulator router. Make sure you put direct-inward-dial on all the dial peers.

On the FXS side (PSTN) disable battery reversal and enable caller-id if you want to pass caller id to emulate just like in the PSTN.



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Re: T1 PRI and FXO PSTN Simulation??

Here is how to set up a 2600 router as a PBX simulator -

Scrounge a 2610 router with 64meg DRAM and 16 meg flash. Load 12.2.15T11 IP Plus or later code. Get an AIM-voice-30 module, E1 or T1 VWIC and a NM-2V/2 port FXS VIC and plug it all together.

Add a config similar to this -

hostname PBX_SIM

isdn switch-type primary-ni

network-clock-participate wic 0

controller t1 0/0

framing esf

linecode b8zs

clock source internal


interface serial 0/0:23

isdn switch-type primary-ni

isdn incoming-voice voice

isdn protocol-emulate network

voice-port 0/0:23

description - PRI port


voice-port 1/0/0

description - fxs port 1


voice-port 1/0/1

description - fxs port 2



dial-peer voice 1 pots

incoming called-number .


port 0/0:23


dial-peer voice 2 pots

destination-pattern 1...

port 0/0:23

forward-digits all


dial-peer voice 3 pots

destination-pattern 2...

forward-digits none

port 1/0/0


dial-peer voice 4 pots

destination-pattern 2...

forward-digits none

port 1/0/1


This will make the T1 PRI port appear as a network side NI PRI service, and with the above config the PRI simulator will have an inwards number range of 2XXX and an outwards number range of 1XXX. The POTS dial peers direct calls between the digital and analogue ports, change the detination patterns to suit your local dial plan.

You can select most ISDN PRI switch types as network side now in the later versions of IOS. Some of the more obscure variants may not be supported, but most work.

The PBX simulator router is using it's internal clock to drive the T1, so the attached device should be set to line clocking.

You then use a T1/E1 cross over cable to connect to the downstream device -

RJ45 RJ45

1 ----------- 4

2 ----------- 5

4 ----------- 1

5 ----------- 2

If you want to use CAS, change the controller to a ds0 group rather than a PRI group.

We use this technique all the time in the TAC lab to test customer configs and it saves us a lot of problems in trying to find PBX or switch 'network' side hardware, it also makes the programming far simpler and more flexible too. It has also been used to conclusively convince customers/telephone companies that the problem lies external to the gateway router - if a network simulator allows calls to be made into/out of the gateway but it stops working when the original line is plugged back in then the heat comes of us.

The NM-HD-2VE and NM-HDV2 cards will do a full TDM connection between ports, so this allows ISDN PRI to BRI data calls, or PRI to analogue ports with DSP bypass. This allows the IOS router to emulate a small PRI/BRI/analogue exchange.

The other option is to use the newer ISR's (2800 or 3800) and have the voice cards located in the HWIC motherboard slots. Either way, the technique works well.

New Member

Re: T1 PRI and FXO PSTN Simulation??

I am aware this is an extremely old post, but what version of IOS is required for this to work. I have a 2610 with an AIM-VOICE-30 and a VWIC-2MFT-T1. My goal is to get this to be a PSTN simulator, but can't figure out which IOS will make everything work. Thanks for any help.

Cisco Employee

Re: T1 PRI and FXO PSTN Simulation??

Any version of 2600 IOS software that is IPplus or IPvoice feature set should work. I haven't played with a 2600 for a while, but there should be 12.3T or 12.4 mainline code available that will give CallManager Express functions as well.

New Member

T1 PRI and FXO PSTN Simulation??

That is what all the literature says. Cisco has pulled all of the 12.2/12.3 T train releases from CCO, minus the a deferred 12.2(15). A quick look shows 12.2 a, b, c or d and 12.3 a,b,c or i. I work for a Cisco partner and know that if some magic IOS was available the router would have to have a valid maintenance contract before i could get a copy of the IOS... oh well.

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