Connect Serial Console with DB9 to RJ45 Adapter

By Innov8 Wholesale Ltd | Published: 2026-10-29

Category: How-to Guides

Learn how to connect a serial console device using a DB9 to RJ45 adapter cable. This guide covers wiring, pinout checks, and common setup mistakes.

Quick answer

Use a DB9 to RJ45 adapter to connect your serial console device to a Cat5 or Cat6 network cable. Ensure the pinout matches your equipment to avoid communication errors.

Why a DB9 to RJ45 adapter works for console connections

A DB9 to RJ45 adapter lets you connect legacy RS232 serial devices to modern structured cabling like Cat5 or Cat6. This is useful for managing network switches, routers, and industrial equipment that still use a serial console port.

The adapter converts the 9-pin serial connector to an RJ45 jack, allowing you to run the connection over long distances using standard Ethernet cable. However, pinout assignments vary by manufacturer, so you must verify the wiring before use.

Common pinout standards and their differences

There are two common pinout standards for DB9 to RJ45 adapters: Cisco (rolled) and standard (straight-through). Cisco devices typically use a rolled cable where pin 1 on one end connects to pin 8 on the other. Other equipment may use a straight-through mapping.

Using the wrong pinout can cause no connection, garbled data, or no power to the serial port. Always check your device manual or the adapter documentation to confirm which standard it follows.

Steps to connect your serial console with a DB9 to RJ45 adapter

1. Identify your console device port: Locate the DB9 female port on your serial console device (e.g., a switch, router, or industrial controller). It is usually labeled 'Console' or 'RS232'. Check the pinout diagram in your device manual before proceeding.
2. Connect the DB9 to RJ45 adapter: Plug the DB9 female end of the adapter into the console port. Ensure it clicks or screws in securely. Then insert an RJ45 patch cable (Cat5 or Cat6) into the adapter's RJ45 jack. A loose connection can cause intermittent communication failures.
3. Connect the other end of the RJ45 cable: Run the RJ45 cable to your computer or terminal server. If your computer does not have a serial port, use a USB-to-serial adapter. Connect the RJ45 end to the adapter or directly to a serial console server. If using a USB adapter, install the driver before connecting the cable.
4. Configure your terminal software: Open a terminal program (e.g., PuTTY, Tera Term, or screen). Set the baud rate, data bits, stop bits, and parity to match your device. Common settings are 9600 baud, 8 data bits, 1 stop bit, no parity. Wrong baud rate will produce garbled characters or no output.
5. Test the connection: Press Enter or send a break signal. You should see a login prompt or command output. If nothing appears, double-check the pinout, cable type, and terminal settings. No response usually means a pinout mismatch or a faulty cable.

Product used in this guide

DB9 9 Pin Serial Female to RJ45 Female Adapter Cat5 Cat6 RS232 to RJ45 Ethernet Console Converter Cable 0.15m: DB9 9 Pin Serial Female to RJ45 Female Adapter Cat5 Cat6 RS232 to RJ45 Ethernet Console Converter Cable 0.15m This short adapter cable is ideal for lab or rack setups where you need a reliable interface between a DB9 serial port and an RJ45 patch cable without extra bulk.
DB9 9 Pin Serial Female to RJ45 Female Adapter Cat5 Cat6 RS232 to RJ45 Ethernet Console Converter Cable 0.15m