Serial Mode

Serial mode allows you to connect to network devices using a USB-to-serial console cable. This is essential for initial device setup, password recovery, and out-of-band management when SSH is not available.

Prerequisites

• A USB-to-serial console cable (RJ45-to-USB or DB9-to-USB)
• The USB cable connected to the probe's USB port
• Physical access to the network device's console port
• The correct baud rate for the target device

Supported Console Cable Types

Cable Type	Connector	Common Use
RJ45-to-USB	RJ45 console port	Cisco, Juniper, Aruba
DB9-to-USB	DB9 serial port	Older switches, industrial devices
USB-C/USB-A to RJ45	RJ45 console port	Modern console cables
USB-C to USB-C	USB-C console port	Some newer devices

Recommended Chipsets

For reliable serial communication, use cables with these chipsets:

• FTDI FT232R — most compatible, recommended
• Prolific PL2303 — widely available
• Silicon Labs CP210x — good compatibility

Avoid counterfeit FTDI cables, as they may not work reliably.

Setting Up a Serial Connection

Step 1: Connect the Cable

1. Connect the USB end of the console cable to the probe's USB port
2. Connect the RJ45/DB9 end to the network device's console port
3. Verify the cable is detected by the probe

Step 2: Add the Device

1. Navigate to CMod > Devices
2. Click Add Device
3. Select Serial as the connection type
4. Configure the serial parameters:

Field	Description	Default
Name	Friendly device name	—
Serial Port	Detected USB serial device	/dev/ttyUSB0
Baud Rate	Communication speed	9600
Data Bits	Number of data bits	8
Parity	Parity checking	None
Stop Bits	Number of stop bits	1
Flow Control	Hardware/software flow control	None
Device Type	Vendor/OS (for template matching)	—

5. Click Save & Test

Step 3: Open Terminal

1. Click the device in the CMod device list
2. Click Terminal
3. An interactive serial terminal opens in your browser
4. Press Enter to wake the device console

Baud Rate Reference

Common baud rates by vendor:

Vendor / Device	Default Baud Rate
Cisco IOS / IOS-XE	9600
Cisco NX-OS	9600
Juniper Junos	9600
HP/Aruba ProCurve	9600
MikroTik RouterOS	115200
Fortinet FortiOS	9600
Palo Alto PAN-OS	9600
Ubiquiti EdgeOS	115200
Linux (generic)	115200

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If you see garbled text in the terminal, the baud rate is likely incorrect. Try the common rates: 9600, 19200, 38400, 57600, 115200.

Serial Communication Settings

Standard 8N1 Configuration

Most network devices use the "8N1" standard:

• 8 data bits
• N (no) parity
• 1 stop bit

This is the default in CMod and should work with the vast majority of devices.

Flow Control

Type	When to Use
None	Default; works for most devices
Hardware (RTS/CTS)	Required by some industrial and older devices
Software (XON/XOFF)	Rarely used; some legacy terminal servers

Serial Port Detection

When a USB serial cable is connected, CMod automatically detects it:

1. Navigate to CMod > Devices > Add Device > Serial
2. The Serial Port dropdown lists all detected USB serial devices
3. If multiple cables are connected, each appears as a separate port (e.g., /dev/ttyUSB0, /dev/ttyUSB1)

If no ports are detected:

• Verify the cable is fully inserted
• Try a different USB port on the probe
• Check the probe's system log for USB device detection errors

Use Cases

Initial Device Setup

When configuring a new-out-of-box switch or router that has no IP address configured:

1. Connect via serial console
2. Complete the initial configuration (assign management IP, enable SSH)
3. Switch to SSH mode for ongoing management

Password Recovery

When locked out of a device:

1. Connect via serial console
2. Follow the vendor's password recovery procedure
3. Reset the password and regain access

Out-of-Band Management

When a device's management interface is unreachable:

1. Connect via serial console
2. Diagnose the issue (interface down, routing problem, etc.)
3. Apply corrective configuration

Firmware Upgrades

Some devices require console access during firmware upgrades:

1. Connect via serial console
2. Monitor the upgrade process in real-time
3. Intervene if the upgrade encounters errors

Troubleshooting

No output in terminal

• Press Enter several times to wake the console
• Verify the baud rate matches the device's configuration
• Try reversing the console cable (some cables are wired differently)
• Ensure the cable's USB driver is loaded (check probe system logs)

Garbled text

• The baud rate is incorrect; try 9600 first, then 115200
• Check data bits, parity, and stop bits settings
• Try a different console cable

"Permission denied" on serial port

• The CMod service requires access to /dev/ttyUSB* devices
• This is configured automatically during NetRecon OS setup
• If using a custom installation, add the CMod service user to the dialout group

Intermittent disconnections

• The USB cable may be loose; ensure a firm connection
• Some long USB cables cause signal degradation; use a cable under 3 meters
• USB hubs can cause issues; connect directly to the probe's USB port

FAQ

Q: Can I use serial mode remotely via Admin Connect? A: Yes. The serial terminal is accessible through the web dashboard, which is reachable via Cloudflare Tunnel. You get the same interactive terminal experience remotely.

Q: How many serial connections can the probe handle simultaneously? A: One serial connection per USB port. Most probe hardware supports 2-4 USB ports. Use a powered USB hub for additional connections, though direct connections are more reliable.

Q: Can I automate serial console commands? A: Yes. Command templates work with serial connections just as they do with SSH. You can create templates for repetitive serial tasks like password recovery or initial setup.

For additional help, contact [email protected].