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Getting access to the ZTE ONT

The ZTE F6005 ONT terminates the TIM FTTH line and sits upstream of the Asus RT-AX86U gateway. This document describes how to reach its management interface, for example to check the optical link status.

Identify the WAN interface on the gateway

The 2.5 Gbps port is eth0 on the Asus RT-AX86U. eth0 is not in the br0 bridge, so it is the WAN interface:

marco@gateway:/tmp/home/root# brctl show
bridge name  bridge id          STP enabled  interfaces
br0          8000.f02f74924f38  yes          eth1
                                             eth2
                                             eth3
                                             eth4
                                             eth5
                                             eth6
                                             eth7

eth0 is the 2.5 Gbps interface:

marco@gateway:/tmp/home/root# ethctl eth0 media-type
Auto Detection of Serdes: Enabled
PHY Capabilities: 2.5GFD|1GFD|100MFD
Link is Up at Speed: 2.5G, Duplex: FD

In previous firmware versions, the 2.5 Gbps interface was eth5.

Reach the ONT

The ZTE ONT has a static IPv4 address: 192.168.1.1. Verify that it is reachable at the data link layer:

marco@gateway:/tmp/home/root# arping -I eth0 192.168.1.1
ARPING to 192.168.1.1 from 192.168.0.2 via eth0
Unicast reply from 192.168.1.1 [28:77:77:24:22:7c] 1.265ms

To reach the ONT from the gateway, add a route to it:

ip route add 192.168.1.1/32 dev eth0

Configure NAT because the ONT doesn't have a route back to the gateway, and sends all traffic to the optical interface:

iptables -t nat -I POSTROUTING -o eth0 -j MASQUERADE

When VLAN tagging is enabled on the WAN connection, connecting through the router doesn't work because the router tags the frames and the ONT doesn't strip the tag: connect an ethernet cable directly to the ONT instead.

Log in

The management interface is at https://192.168.1.1 (self-signed certificate). The credentials are the vendor defaults, which are easy to guess and publicly documented:

  • User: admin
  • Password: admin

Automation

The manual procedure above has been automated as part of the ONT monitoring stack that the ferrarimarco_home_lab_node Ansible role deploys:

  • config/ansible/roles/ferrarimarco_home_lab_node/files/config/monitoring-ont/configure-route-to-ont.sh configures access to the ONT idempotently: it discovers the WAN interface from nvram get wan_ifname, adds the route and the MASQUERADE rule if missing, and assigns a local address on the ONT subnet to the WAN interface.
  • config/ansible/roles/ferrarimarco_home_lab_node/files/config/monitoring-ont/zte-f6005-ont-exporter.py is a custom Prometheus exporter that logs in to the ZTE F6005 management interface and exports its metrics.
  • The systemd services and timer in config/ansible/roles/ferrarimarco_home_lab_node/templates/monitoring-ont orchestrate the two: monitoring-ont-network-config.service (triggered by its timer) runs the network configuration script, and zte-f6005-ont-exporter.service runs the exporter.

References