binding voice-port to specific timeslot

Answered Question
May 7th, 2008

Dear all,

I have a pbx and cisco 2821 with vwic.

i want to OPX on my router.

So on my pbx cas is configured with 30 specific number. on router side i have configured 30 seperate DS0 channel to achive 30 dedicated voice-port.

i have als0 30 FXS port on my router.

how can bind each fxs port into specific timeslot?

any idea?

Correct Answer by Paolo Bevilacqua about 8 years 9 months ago

Each fxs had a different plar string for a different timeslot. Any fxs is ok for that.

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Overall Rating: 4.7 (3 ratings)
Paolo Bevilacqua Wed, 05/07/2008 - 11:50

Hi, you've asked this question already, which signaling type do your PBX uses ?

Eg, if E1 R2, is not necessary to assign each port to a timeslot.

miskoolak Wed, 05/07/2008 - 11:58

the signalling between pbx and router is fxo-loop-start.

i have provided the connection between pbx phone extension into fxs ports.

but the problem is when you dial-out from fxo phone into pbx every time one number is appeared on pbx phone extension.

it seems some kind of round robin between dso timeslot..but i need one fxs phone uses just one and specific ds0 timeslot for dial-out.

any way thank you for you follow up my friend.

Paolo Bevilacqua Wed, 05/07/2008 - 13:10

Ok. Remove the 'cas-group' under controller. Configure instead 30 times, cas-group number from 1 to 31 with the correct timeslot - remember you have to skip 16.

Configure 30 dial-peers, one for each of the new 30 voice-ports that are consequently created, with destinaion-patter like C01 ... C31.

Under the voice-ports for fxs, configure "connection trunk Cxx" with xx being number for the corresponding timeslot.

This way, as soon you lift phone, you will have dial-tone from PBX.

miskoolak Thu, 05/08/2008 - 00:36

HI dear bevilacqua ;

according to your idea I have to small mistake.

I have to define "Connection PLAR ####" for each logical voice port "voice-port 0/3/0:1"

to make pbx extention call into fxs phones..

---here my config------

controller e1 0/3/0

ds0-group 1 timeslot 1 type fxo-loop-start

ds0-group 1 timeslot 1 type fx0-loop-start



voce-port 0/3/0:1

connection plar 40001


connection plar 40002


voice-port 0/1/0

description fxs port

voice-port 0/1/1

description fxs port



dial-peer voice 40001 pots

port 0/1/0

destination-pattern 400001


dial-peer voice 40002 pots

port 0/1/1



dial-peer voice 41000 pots

port 0/3/0:1

forward-digit all

dial-peer voice 41001 pots

port 0/3/0:2

forward-digit all




4100X are my pbx extension

behinde my pbx I have about 100 extensions

how can i dial all of them from my fxs phones??


calls from pbx to fxs are woking fine.

Paolo Bevilacqua Thu, 05/08/2008 - 02:17


under DP 41000 ... 41030 you need destination-pattern. I suggest to use Cxx, but you can use anything that is configured as connection plar under fxs port.

miskoolak Thu, 05/08/2008 - 03:01

please tell me how PBX dial tone will provided?

and what is your meaning with CXX?

Paolo Bevilacqua Thu, 05/08/2008 - 03:20

Once plar completes, fxo goes off hook and you have dialtone. Cxx are just numbers, you can use others.

miskoolak Thu, 05/08/2008 - 03:51

You mean that I should provide "connection plar XXXX" under my FXS voice-port?

that XXXX mentions to PBX phone extension number?

then how it understand to select proper dso timeslot..(To prevent worng caller id on pbx extension)

thank you again.

miskoolak Thu, 05/08/2008 - 03:52

teh other poitn is that is FXS-DID needed for this isuue or normal FXS can handel it?

Correct Answer
Paolo Bevilacqua Thu, 05/08/2008 - 04:00

Each fxs had a different plar string for a different timeslot. Any fxs is ok for that.


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