Modem Pass through to remote PBX

Question

Dear All,
I would like to use the cisco router 3640 (with T1 card) and cisco 2621 (with 2 x FXS card) to simulate the network & pstn environment to test the modem pass through, here is the detail connection:
Analog Phone (Ext: 451660) <--> [FXS] Cisco Router 2621 <---- LAN ----> Router 3640 [T1] <--> [T1] PBX (Panasonic) <--> Analog Phone (Ext: 454820, Modem)
The dial-peer on the router 2621 & 3640 is working as I can call in/out from PBX analog phone, and I was success to connect the PC (with modem port, and use the hyperterminal, atdt454820) from Outside PC (with modem port, Ext: 451660).
But I was fail to dial-out from PBX analog phone (454820) to 451660.
From Cisco router 2600:
dial-peer voice 45166 voip
destination-pattern 45166.
modem passthrough nse codec g711ulaw redundancy
session target ipv4:192.168.0.60 (Router 3640)
From Cisco router 3640
dial-peer voice 454820 voip
destination-pattern 454820
modem passthrough nse codec g711ulaw redundancy
session target ipv4:192.168.0.44 (Router 2600)
Here is the link I try to follow to do:
http://www.cisco.com/en/US/docs/ios/12_1t/12_1t3/feature/guide/dtmodptr.html
I would like to know if there is any miss-configure or how can I troubleshoot (to find out the cause) which I cannot connect from PBX' PC.
Thanks!

Answer 1

Note that anytime a call traverses a voice gateway, we match *two* dial-peers, not one.  We match one inbound, and one outbound.  In your scenario, if the FXS side originates the call, it would be:
fxs(inbound pots)router(outbound voip)----LAN-----(inbound voip)router(outbound pots)---T1
The algorithm for how this works is documented in this link.  I recommend having a few reads over this:
http://www.cisco.com/en/US/tech/tk652/tk90/technologies_tech_note09186a008010fed1.shtml
If you can get these debugs, I can take a deeper look into the failure:
debug voip ccapi inout
debug isdn q931
debug vpm sig
debug h225 asn1
debug h245 asn1
Collect these in the following manner:
Router(config)# service sequence
Router(config)# service timestamps debug datetime msec
Router(config)# logging buffered 10000000 7
Router(config)# no logging con
Router(config)# no logging mon
Router(config)# voice iec syslog
Router# term len 0
Router# sh logg
Also send the full configs of both gateways.
-Steve