A serial console is a hardware interface often used for initial configuration and troubleshooting of networking devices such as switches, routers, and firewalls. This is more practical when the device’s network connection is not yet ready or not working properly. A serial console will provide you with a command-line interface (CLI) that enables you to access and configure the device. From the console you can enter commands and receive output from the device in real-time, similar to using a command prompt or terminal window.

Netgate is a company known for making networking network appliances based on the open-source pfSense software. The appliances are designed to be used in small to medium-sized businesses, as well as home users and enthusiasts. In our Lab environment we’re running Netgate pfSense SG-2100. This appliance fills the gap between SG-1100 and SG-3100 devices.

Netgate SG 2100

Netgate SG-2100 pfSense Plus Appliance features:

  • CPU: Dual Core Cortex-A53 ARM64 Soc @ 1.2GHz
  • Memory: 4 GB DDR4
  • Storage: 8 GB eMMC (upgradable)
  • Network Ports: (1) GbE (RJ45/SFP) WAN port, (4) 1 GbE switched LAN ports with 2.5Gbps uplink

You can get one from Amazon.

Connecting to Serial Console on Netgate Appliance

The Netgate hardware I’m working on has a serial console. We need a client PC with an appropriate port and terminal software to connect to its console.

For most firewalls purchase from Netgate store, connecting to a serial console requires correct hardware, including:

  • A client PC with a physical serial port or a USB-to-Serial adapter
  • A physical serial port on the Netgate appliance
  • A null modem serial cable and/or adapter, or a device-specific serial cable
  • A terminal program on the client, such as PuTTY, or screen for Linux / macOS
  • The correct serial settings on the client software

My appliance has MiniUSB console cable included in the box – USB A to Mini-B cable

usb mini adapter
One end connects to Netgate appliance, and another to your PC

If the appliance you’re working on has a serial console port, you’ll need this type of cable.

usb serial

But for most Netgate appliances the hardware required is a USB A to Mini-B cable.

Step 1: Install serial console client program

A serial console client program has to be installed on your client PC.

Linux / macOS – use screenor minicom

### Install screen on RHEL Based systems ###
sudo yum -y install screen minicom

### Install screen on Debian Based systems ###
sudo apt update
sudo apt install screen minicom

### Install screen on macOS ###
brew install screen minicom

Windows – Install one of the following programs on your Windows system.

Step 2: Connect a Serial Cable

Connect a serial cable between Netgate appliance and your client PC. If your PC does not have a physical serial port, use a USB-to-Serial adapter. Once connected we need to locate the client Serial Port.

  • Linux: USB-to-Serial adapter is likely to show up as /dev/ttyUSB0. You can attach and check with dmesg
  • macOS: Run the command ls -l /dev/cu.* to list available devices after connecting.
$ ls -l /dev/cu.*
crw-rw-rw-  1 root  wheel  0x9000001 Apr  6 13:26 /dev/cu.BLTH
crw-rw-rw-  1 root  wheel  0x9000003 Apr  6 13:26 /dev/cu.usbserial-14230

The name follows syntax /dev/cu.usbserial-<id>

  • Windows: A a physical serial port is typically COM1. For USB-to-Serial adapter, it may be COM3. To validate open Device Manager in Windows and expand Ports (COM & LPT) to check port assignment.
  • FreeBSD: On FreeBSD the device associated with a USB-to-Serial adapter will likely be /dev/cuaU0

Step 3: Launch serial client program on PC

Once the cable is connected we can launch appropriate client application for our client system. The settings for the serial port, including the speed, must be known before a client can successfully connect to a serial console.

  • Speed: 115200 – this is the default speed pfSense software uses out of the box (must specify)
  • Data Bits: 8
  • Parity: No
  • Stop Bits: 1

This is typically written as 115200/8/N/1.

Start a Serial Client

Windows – PuTTY
  • Start PuTTY
  • Select Serial for the Connection Type
  • Enter the serial port device name for Serial Line, e.g. COM3 or /dev/ttyUSB0.
  • Enter the appropriate Speed, e.g. 115200
  • Click Open
macOS

Screen: Press Ctrl-A, \ to quit, or Ctrl-A, Ctrl-\ in some cases.

sudo screen -U /dev/cu.usbserial-<ID> 115200

Minicom

minicom -D /dev/ttyUSB0 -R 115200
Linux

Screen: Press Ctrl-A, \ to quit, or Ctrl-A, Ctrl-\ in some cases.

sudo screen /dev/ttyUSB0 115200

Minicom

minicom -D /dev/ttyUSB0 -R 115200

Sample screen output:

Boot process:

You can now power on the Netgate appliance, and watch the console output in your terminal emulator program.

pfsense screen serial netgate 01

You should see the boot process and login prompt.

pfsense screen serial netgate 02

From here, you can configure and manage the Netgate appliance using the command-line interface. Once you are done, you can exit the console connection and unplug the serial cable.

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