XGS-ONU-25-20NI on Proximus Fiber

FS.com XGS-ONU-25-20NI (XGS-GPON) on Proximus (BE) / KPN (NL)

This guide explains how to use the XGS-ONU-25-20NI XGS-GPON SFP+ ONU module from FS.com with:

• Proximus Fiber (Belgium)
• KPN Fiber (The Netherlands)

I originally posted this guide in Dutch, but since clear English instructions are hard to find, this README provides a complete step-by-step explanation.

Update 2026: The procedure has been simplified.

⚠️ Disclaimer

This guide describes advanced configuration steps.
Proceed at your own risk. You are responsible for any changes made to your equipment.

📦 Requirements

• FS.com XGS-ONU-25-20NI module
• SFP+ compatible router or SFP+ adapter
• Active fiber connection
• Login credentials from FS.com

🔑 Step 1 — Obtain ONU Credentials

After ordering the module, contact your FS.com representative and request:

• Username
• Password

The username is also the GPON Serial Number (SN).

You will need this serial number when registering the module with your ISP.

📝 Step 2 — Register the Module (Proximus)

Log in to MyProximus and navigate to:

  → Products
  → Internet XXXX Fiber
  → Install your own equipment
  → Register your own fiber modem

Enter the GPON serial number (the ONU username).

🌐 Step 3 — Connect to the ONU

The module runs a Telnet server at:

192.168.100.1

⚠️ This IP is only reachable when the fiber link is connected and active.

I used a Thunderbolt to SFP+ adaptor from QNAP connected to my laptop

Example Setup

1. Insert the ONU into an SFP+ adapter.
2. Connect the fiber cable.
3. Configure your computer manually:

IP Address: 192.168.100.2
Netmask:    255.255.255.0

💻 Step 4 — Access via Telnet

Open a terminal:

telnet 192.168.100.1

Log in using the credentials provided by FS.com.

🛠 Step 5 — Configure ETH UNI Slot to 1

Run the following commands:

ONT> enable
#ONT> system/shell
#ONT/system/shell> echo "ETH10GESLOT=1" > /mnt/rwdir/sys.cfg
#ONT/system/shell> reboot

The module will reboot with the correct configuration.

🌍 Step 6 — Install in Your Router

1. Insert the ONU into your router’s SFP+ WAN port
2. Attach your fibre cable
3. Configure your WAN interface

Proximus Configuration

Don’t forget to use VLAN 20.

🔄 Reverting the Changes

To restore the default configuration:

ONT> enable
#ONT> system/shell
#ONT/system/shell> rm /mnt/rwdir/sys.cfg
#ONT/system/shell> reboot

📚 Reference

FS.com Command Manual:
https://resource.fs.com/mall/doc/20230721113630xfzpbl.pdf

✅ Summary

• ONU username = GPON Serial Number
• ONU password = Get this from your FS.com rep
• ONU management IP: 192.168.100.1 (fiber must be connected)
• Change ETH UNI Slot to 1
• Proximus requires VLAN 20