Port 2246: pc-mta-addrmap — The Cable Phone Provisioning Port

Port 2246 is registered with IANA as pc-mta-addrmap — PacketCable MTA Address Mapping. It runs on both TCP and UDP.

What It Does

PacketCable is the CableLabs specification that lets cable Internet providers offer voice phone service over their broadband networks. It's the infrastructure behind cable phone service — the kind where you plug a regular analog telephone into a device attached to your cable modem and it just works.

The MTA in pc-mta-addrmap stands for Multimedia Terminal Adapter. An MTA is the hardware that bridges the gap between the cable network's digital VoIP infrastructure and the analog phone plugged into your wall. Most customers never see a standalone MTA — it's typically embedded directly in the cable modem itself, creating what the industry calls an eMTA (embedded Multimedia Terminal Adapter).¹

Port 2246 specifically handles the address mapping phase of MTA provisioning — the step where the network resolves the MTA's identity to a usable address so it can receive its configuration. This is part of the broader PacketCable provisioning sequence, which involves DHCP, DNS, TFTP, and Kerberos-based authentication working in sequence before the MTA is ready to carry calls.²

The Provisioning Dance

When a cable modem with an embedded MTA boots up, it doesn't just start working. It goes through a multi-step initialization:

1. The cable modem comes online and gets its IP address
2. The MTA component registers separately, also via DHCP
3. DNS resolves the MTA's identity to locate provisioning servers
4. The MTA downloads its configuration (the VoIP settings, codec parameters, server addresses)
5. Optionally, Kerberos authentication establishes a secure channel

Port 2246 participates in steps 2–4 of this flow. The address mapping service helps the provisioning infrastructure locate and identify the MTA so the right configuration gets delivered to the right device.³

Who Uses It

This port matters to:

• Cable operators running PacketCable voice services (Comcast, Cox, Charter, and similar providers)
• Network equipment vendors building cable modems with embedded voice capability (Arris, Cisco, Technicolor, and others)
• Broadband Access Center servers — Cisco's term for the server-side provisioning infrastructure that manages eMTA devices at scale

If you're troubleshooting cable VoIP provisioning and see port 2246 blocked or failing, the MTA likely can't complete its address resolution phase, and the phone won't register.

Port Range

Port 2246 falls in the registered ports range (1024–49151). These ports are registered with IANA by companies and standards bodies for specific applications, but unlike the well-known ports below 1024, they don't require elevated privileges to bind on most operating systems.

The registered range exists precisely for services like PacketCable — real, widely-deployed protocols that need a stable, collision-free port assignment without being fundamental enough to occupy the sub-1024 space reserved for core Internet infrastructure.

Checking What's Listening

To see if anything is using port 2246 on your system:

macOS / Linux:

# Show processes listening on port 2246
sudo lsof -i :2246

# Or with ss (Linux)
sudo ss -tlnp sport = :2246

Windows:

netstat -ano | findstr :2246

On a typical workstation or server, you'll find nothing — port 2246 is relevant only to cable network infrastructure, not end-user machines. If something unexpected is listening here, it's worth investigating.