A GPON subscriber goes from spliced drop cable to working internet in about ninety seconds of CLI — but only if the optical work before it was done properly. This is the workflow I run on ZTE C320 and C300 OLTs, in the order it actually happens on site.
Before you touch the OLT#
Measure first. Roughly 80% of "provisioning problems" are optical problems wearing a config costume.
| Reading | Healthy | Action if outside |
|---|---|---|
| ONU RX power | −15 to −25 dBm | Re-clean connectors, inspect splice, re-check splitter ratio |
| OLT RX from ONU | −13 to −27 dBm | Suspect a dirty or bent drop fibre |
| Splice loss | < 0.1 dB | Re-splice |
| Connector loss | < 0.5 dB | Clean with a one-click cleaner, re-measure |
A 1:32 splitter costs about 17–18 dB of budget on its own. Two cascaded splitters plus a long feeder is how you end up at −28 dBm and a link that only fails when it rains.
1. Discover the ONU#
ZXAN# show gpon onu uncfggpon-onu_1/1/1:1 ZTEGC1A2B3C4 unknown
The serial matches the label on the ONU. If nothing appears, stop and go back to the optical table above — do not "try another port".
2. Authenticate and bind#
ZXAN# configure terminalZXAN(config)# interface gpon-olt_1/1/1ZXAN(config-if)# onu 1 type ZTEG-F660 sn ZTEGC1A2B3C4ZXAN(config-if)# exit
Keep the ONU index deliberate — index 1–32 mapped to a documented customer ID. Random indexes make the second engineer's life miserable.
3. Service configuration#
ZXAN(config)# interface gpon-onu_1/1/1:1ZXAN(config-if)# name CUST-10432ZXAN(config-if)# tcont 1 name INTERNET profile 30M-upZXAN(config-if)# gemport 1 tcont 1ZXAN(config-if)# service-port 1 vport 1 user-vlan 100 vlan 100ZXAN(config-if)# exit
The T-CONT carries the upstream bandwidth contract, the GEM port carries the traffic, and the service port maps the subscriber VLAN. All three or nothing works.
4. Bandwidth profiles#
Define profiles once, reuse them for every plan:
ZXAN(config)# gponZXAN(config-gpon)# profile tcont 30M-up type 3 assured 20480 maximum 30720
Type 3 (assured + maximum) is the right default for residential: a guaranteed floor with burst headroom. Type 1 fixed bandwidth wastes capacity on a shared PON.
5. Verify before you leave#
ZXAN# show gpon onu state gpon-olt_1/1/1ZXAN# show pon power attenuation gpon-onu_1/1/1:1ZXAN# show gpon onu detail-info gpon-onu_1/1/1:1
State must read working, and attenuation should sit under 25 dB. Then run an actual speed test from the customer premises — the OLT saying "working" and the customer having internet are different claims.
Recurring field faults#
- ONU flapping every few minutes. Almost always a marginal splice or a macro-bend in the drop cable at the wall entry. Check RX power over time, not once.
- LOS on the whole port after a storm. Feeder damage or water in an unsealed closure. Check the port before assuming thirty ONUs failed independently.
- One subscriber slow, everyone else fine. Wrong T-CONT profile applied, or the ONU's LAN port negotiated at 100 Mbps.
- New ONU refuses to register. Serial already bound elsewhere.
show gpon onu by snfinds it.
Documentation that pays for itself#
For every activation, record: customer ID, ONU serial, OLT/port/index, VLAN, plan profile, RX power at activation. That last figure is the baseline you compare against when the same customer complains eight months later — and it turns a two-hour diagnosis into a two-minute one.
