Multicast Switching Protocol

Nov 04, 2025

Overview

In a Just Add Power video distribution system, Multicast Switching is a method of source switching that changes the multicast IP of a Decoder—called a Channel—to match the multicast IP of the Encoder it should display.

Channel changes can be triggered in multiple ways depending on the control system or user interface. Two system modes are available:

Unified Mode: Audio, video, and USB share the same Channel.
Flexible Mode: Each service (audio, video, USB) can use a unique Channel. All devices in the system must use the same Mode.

Use AMP Software to set up devices for Multicast Switching automatically.

Requirements

Compatible with Omega, Ultra, and MaxColor Series devices
justOS firmware version B2.1.0 or newer
All devices must be on the same VLAN and within the same IP scheme

For network setup guidance, see Multicast Switching for Single VLAN Implementations.

Firewall & Ports

Telnet (CLI): TCP 23 — Used for Encoder/Decoder configuration (Unified/Flexible selection, astparam). Plain text; restrict to trusted VLANs.
HTTP API (justAPI): TCP 80 — Used for control calls like POST /cgi-bin/api/command/channel. Keep internal; do not expose publicly.

Best practice: place Just Add Power devices on a management VLAN, allow only required ports from authorized controller IPs, and block external access.

Concept

In a Multicast Switching system, audio, video, and USB data are distributed based on their multicast IP addresses. To simplify configuration, each multicast IP corresponds to a Channel number.

Audio and Video use separate multicast IPs, allowing independent routing.
Each Encoder has a unique multicast IP address.
Each Decoder changes its Channel to match the Encoder it should receive from.

Default Multicast IPs

Unified Mode — Audio, video, and USB switch together (default)

Video — 239.92.0.0
Audio — 239.92.0.0
USB — 239.92.0.0

Flexible Mode — Audio, video, and USB can switch together or independently

Omega & Ultra Series

Video — 239.92.0.0
Audio — 239.93.0.0
USB — 239.94.0.0

MaxColor Series

Video — 239.92.0.0
Audio — 239.93.0.0
USB — 239.97.0.0

Multicast IP to Channel Translation

The multicast IP structure defines how Channels are derived:

The first two octets must match on all devices.
- The first octet may be changed, but it must be consistent across the system.
- The second octet defines the service type (e.g., audio or video).
The last two octets uniquely identify each Encoder and map directly to its Channel number.
Channel numbers range from 0–9999.

Channel	Multicast IP
`0000`	`239.92.00.00`
`0099`	`239.92.00.99`
`0100`	`239.92.01.00`
`9999`	`239.92.99.99`

Telnet Protocol

Telnet is the primary method for sending CLI (Command Line Interface) commands directly to Just Add Power Encoders and Decoders. It provides low-level access to device settings such as channel control, IP configuration, and mode selection.

Connection Details

Protocol: Telnet
Port: 23 (default)
Default login: No authentication required
Session type: Plain-text command interface

Telnet connections can be made using applications such as PuTTY (Windows) or the built-in telnet command (macOS/Linux).

Usage Notes

Use Telnet when sending configuration commands like channel mode advanced or astparam strings.
Each command must be sent as a complete line followed by the Enter key.
Telnet sessions are intended for quick, local configuration—avoid leaving open connections active.
Only one Telnet session can modify device parameters at a time.
channel mode basic = Unified Mode
channel mode advanced = Flexible Mode

Security Considerations

Telnet operates as a clear-text protocol on port 23 and does not encrypt data. For secure network environments, isolate Just Add Power devices on a trusted VLAN or management network. Avoid exposing port 23 to public or untrusted segments of a LAN/WAN.

Unified Mode Commands

AMP Alternate Configuration builds systems in Unified Mode and applies both Channels and Management IPs. Use the following commands only if not using AMP.

All commands are case-sensitive.

Set Unified Mode (default)

Applies once system-wide. All services switch together.

channel mode basic

Note: The CLI keyword is basic, which corresponds to Unified Mode.

Set Audio & Video Channel

Configure on an Encoder or send to a Decoder to change the active source. Replace $ChannelNumber with a value between 0–9999.

channel $ChannelNumber

Set Management IP (Encoder & Decoder)

Example static configuration:

astparam s ip_mode static;astparam s ipaddr 172.17.128.1;astparam s netmask 255.255.0.0;astparam s gatewayip 172.17.255.254;astparam save

Note: Send commands using PuTTY or Windows Telnet. Do not use the device web interface.

Flexible Mode Commands

Use Flexible Mode for independent per-service switching.

All commands are case-sensitive.

Set Flexible Mode

Allows each service to switch independently. Apply once, then reboot all devices.

channel mode advanced

Note: The CLI keyword is advanced, which corresponds to Flexible Mode.

Set Audio Channel

channel -a $ChannelNumber

Set Video Channel

channel -v $ChannelNumber

Set USB Channel

channel -u $ChannelNumber

Set Management IP (Encoder & Decoder)

Example static configuration:

astparam s ip_mode static;astparam s ipaddr 172.17.128.1;astparam s netmask 255.255.0.0;astparam s gatewayip 172.17.255.254;astparam save

Note: Send via PuTTY or Telnet. Avoid the web interface.

HTTP API

The complete HTTP API for justOS is documented here.

HTTP API Channel Command

Unified Mode only. The POST /cgi-bin/api/command/channel endpoint switches a Decoder to a specific Channel in Unified Mode, where audio, video, and USB change together.

Endpoint Details

Method: POST
URI: /cgi-bin/api/command/channel
Content-Type: application/json (or text/plain)
Return: application/json ({"data":...} on success, {"error":...} on failure)
Port: 80 (HTTP)
Firmware: justOS B2.1.0 or greater

Request Body

Provide the Channel number (integer 0–9999) that the Decoder should join:

{
  "cmd": "set",
  "channel": 100
}

Example Request

POST http://172.17.128.25/cgi-bin/api/command/channel
Content-Type: application/json

{
  "cmd": "set",
  "channel": 100
}

Responses

{"data":"ok"}

{"error":"invalid request"}

All justAPI responses are returned in JSON envelopes:

"data" — Indicates success.
"error" — Indicates a problem (such as an invalid parameter or Channel number outside 0–9999).

Usage Notes

Applies only to Unified Mode. Audio, video, and USB switch together.
Channel range: 0–9999.
Command executes immediately; no reboot required.
Send one request at a time and wait for the response before sending another.
Ideal for control systems such as Crestron, Control4, and Q-SYS.