World's Simplest VWIC T1 Config?

Can somebody please tell me what I'm doing wrong here -- attempting to make a call from a phone on R1 to a phone on R2. Doesn't get much simpler than that. They're connected by an MFT1 T1 with a T1 crossover. There are no alarms. I have been trying to force some combination of FXO and FXS connection for a while now without luck.

R1
tdm clock T1 3/0 voice export line
voice-card 3
controller T1 3/0
framing esf
linecode b8zs
ds0-group 0 timeslots 1-2 type fxo-loop-start
ds0-group 1 timeslots 3-4 type fxs-loop-start

voice-port 3/0:0
output attenuation 0
!
voice-port 3/0:1
output attenuation 0
!
!
dial-peer voice 2 pots
destination-pattern 1...
port 3/0:0
!
!

R2
tdm clock T1 3/0 voice export line
voice-card 2
!
voice-card 3
!
controller T1 3/0
framing esf
linecode b8zs
ds0-group 0 timeslots 1-2 type fxo-loop-start
ds0-group 1 timeslots 3-10 type fxo-loop-start
!
!
!
!
!
voice-port 3/0:0
output attenuation 0
!
voice-port 3/0:1
output attenuation 0
!
!
dial-peer voice 55 pots
description to other
preference 1
destination-pattern 2...
port 3/0:0

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Comments

azaghul

Hi,

Looks like you're using 1760's (a great entry level voice router!) and there are a number of areas to look at.

Both R1 and R2 are set to receive clocking. You'll need to set one side as network to supply clock. The 1700 series has a very unintuitive method of clocking.

Set one side to;

tdm clock T1 3/0 voice import onboard internal

this will take clock from the on-board internal router clock (PLL) and import it into the VWIC card. Look for a doc at Cisco called "Clock Configuration for Cisco 1751/1760 Routers" which explains it fairly well.

DS0 group 1 has a mismatch on the number of timeslots allocated between the R1 and R2. There is also a mismatch in FXS/FXO signalling between them.

There is also a missing dial peer to process incoming calls for each router, something like;

dial-peer voice 1 pots
 desc *** Inbound Matching ***
 incoming called-number .
 direct-inward-dial
 exit

This should get you headed in the right direction.

An FYI, if you decide to change from CAS to PRI, you'll need to move the T1's to WIC/VWIC 0 or 1, it's just another oddity of the 1760.:)

azaghul

In a T1 world where there are 24 channels;

CAS (Channel Associated Signalling) embeds the call setup, teardown, and signalling within each of the 24 channels.

PRI/CCS (Common Channel Signalling) on the other hand, reduces the available channel count to 23, and designates channel 24 to carry call setup, teardown, and other signalling.

All this, and much more, is covered in CVOICE / CCVP.