In some countries the Telco would send the digits in overlap and not as en-block.
En-bloc dialling expects all the information (esp the called party number) in one set up message.
In overlap receiving the information is not received in one message. Additional information elements are required for the call to be routed properly.
The overlap receiving can be seen in the debug q931:
The first set up message does not have the complete digits for the called party number. Additional information elements follow thereafter for the called digits:
The number dialled in this case is 9586874
060298: May 30 08:36:51.269: ISDN Se0/0/0:15 Q931: RX <- SETUP pd = 8 callref = 0x72BC
Bearer Capability i = 0x8090A3
Standard = CCITT
Transfer Capability = Speech
Transfer Mode = Circuit
Transfer Rate = 64 kbit/s
Channel ID i = 0xA98391
Exclusive, Channel 17
Calling Party Number i = 0x2181, '6224143323'
Called Party Number i = 0xC1, '95868'
High Layer Compat i = 0x9181
060299: May 30 08:36:51.269: ISDN Se0/0/0:15 Q931: Received SETUP callref = 0xF2BC callID = 0x12BE switch = primary-net5 interface = User
060300: May 30 08:36:51.269: ISDN Se0/0/0:15 Q931: TX -> SETUP_ACK pd = 8 callref = 0xF2BC
Digit "7" being sent by the Telco as Additional Information Element:
060301: May 30 08:36:51.457: ISDN Se0/0/0:15 Q931: RX <- INFORMATION pd = 8 callref = 0x72BC
Called Party Number i = 0xC1, '7'
Digit "4" being sent by the Telco as Additional Information Element:
060302: May 30 08:36:51.725: ISDN Se0/0/0:15 Q931: RX <- INFORMATION pd = 8 callref = 0x72BC
Called Party Number i = 0xC1, '4'
In case the numbers are received as overlap, the following changes are advised on the router:
Avoid using the translations on the voice-ports. Use them on the incoming dial-peers rather.
interface serial 0/0/0:15
isdn overlap-receiving t302 <time in milliseconds>
Incoming Dial Peer:
dial-peer voice 1 pots
incoming called number .T
The important thing to note is that direct inward-dial should not be configured in the incoming dial-peer
dial-peer voice 2 voip
destination-pattern .T <<<< the destination pattern in the outgoing dial-peer should terminate with .T
Another thing to note is the sending complete message.
060319: May 30 08:37:18.897: ISDN Se0/0/0:15 Q931: RX <- INFORMATION pd = 8 callref = 0x72BD
Incase the information element has the sending complete message the wait timer t302 would stop and the next step of matching the outgoing dial-peer would proceed:
Links for reference:
Understanding Inbound and Outbound Dial Peers Matching on IOS Platforms: