Generate IOS-XE config for PRI T1 or E1 voice gateway: controller, ISDN switch type, D-channel, framing, and protocol binding (MGCP / H.323 / SIP) to CUCM.
PRI config spans the physical controller, the D-channel, signaling protocol binding, and dial peers. Miss one line and calls don't go through. This generator emits a full working block for your circuit type and carrier.
Set inputs, click Generate PRI config.
Physical circuit settings.
D-channel interface.
Voice-port + encoding.
Route to CUCM.
Switch-type mismatch: if your carrier provisioned the circuit as NI (National ISDN) and you configure isdn switch-type primary-5ess, the circuit physically comes up (LED green), Layer 2 (LAPD) comes up, but no calls can complete. You'll see "PRI Layer 3 errors" in show isdn status. Always verify with the carrier: "What's the switch type on our Q.931?"
Clock source: T1/E1 must have exactly ONE clock source in the circuit. The carrier always provides clock from their central office — your router should use clock source line on the controller. Using internal on both ends causes slips, then errors, then the circuit drops. If you have multiple PRIs from the same carrier, only one should be line; the others should be line secondary or follow the primary.
Framing/encoding mismatch: T1 needs ESF framing + B8ZS encoding for modern ISDN. Older circuits might use SF/AMI but ISDN PRI requires ESF. E1 needs CRC4 framing + HDB3 encoding. If these don't match on both ends, you get Layer 1 alarms (yellow alarm, red alarm). The LED on the NIM tells you Layer 1 state; show controller t1 0/2/0 tells you the details.
Protocol binding (SIP/MGCP): the dial peer or voice port needs to know where to send calls. For SIP: dial-peer voice X voip with session target ipv4:<cucm>. For MGCP: mgcp call-agent <cucm> + tie voice-port to MGCP. Don't mix — one protocol per gateway. SIP is preferred in 2026; MGCP requires CUCM manages the gateway state.
show isdn status — you want Layer 1 ACTIVE, Layer 2 MULTIPLE_FRAME_ESTABLISHED, Layer 3 OPERATIONAL.
Much older, no D-channel. Use only for very legacy tie lines. Different config — ds0-group instead of pri-group.
Per voice port / DS0, yes — but complex. Best to pick one.
debug isdn q931 (verbose). Look at call SETUP → CONNECT flow.
50 users.
PBX tie.
Call center, all MGCP.
Our Upgrade Sprints convert legacy PRI circuits to SIP trunks with parallel run, failback, and documentation.