Notes to remeber

    • Only one protocol type is supported under auto registration
    • Use loopStart for analog device
    • Use groundStart for connecting to another PBX
    • ISDN use Q.931 signaling protocol
    • Q.931 used for DNIS , ANI , transfer ,hold , etc
    • DNIS : Dialed Number Identification Service (used to determine the DID or called number)
    • ANI : Automatic Number Identification (Caller ID)
    • CCS : Common channel signaling (it used a dedicated channel for the signaling )
    • CAS : Channel Associated Signaling (it use 2 or 4 bit in the same frame of the data for signaling)
    • Two-stage dialing :The router/gateway then presents a dial tone to the caller and collects digits until it can identify an outbound dial peer.dial-peer matching is done digit-by-digit. This means the router/gateway attempts to match a dial peer after each digit is received
    • One-stage dialing : if the PBX or CO switch sends a setup message containing “all” the digits necessary to fully route the call, those digits can be mapped to an outbound Voice-Network dial-peer directly. With DID, the router/gateway does not present a dial tone to the caller and does not collect digits. It forwards the call directly to the configured destination
    • For inbound dial peers, the session target command is ignored.
    • when the isdn overlap-receving command is configured on ISDN interfaces. After every digit is received at the ISDN layer, dial peers are checked for matches. If a full match is made, the call is routed immediately


  1. Q.931 :Call Setup , Setup ACK , Call Proceeding, Alert,  Connect , Connect Ack


  • H225 : setup
  • H245 : Features
  • H261 , H263 : Video
  • H225 RAS : Gate-keeper
  • RTCP: Statistics
  • T.123 ,T.124,T.125 : Application (Real time)

debug vpm : used for debuging FXO ports

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