📡 Monitoring an OLT with SNMP

ISPMan monitors OLTs (Optical Line Terminals) over SNMP. An OLT usually sits on the local network behind one of your managed routers. This guide shows how to add the OLT to ISPMan, allow ISPMan to reach it through that router, and enable SNMP on the OLT itself.

📋 Prerequisites

• The router the OLT sits behind is added to ISPMan and online.
• You know the OLT's local IP address (the address it has on the router's LAN, e.g. 192.168.1.10).
• You can log into the OLT's web or CLI to enable SNMP.

Step 1 — Add the OLT in ISPMan

Go to Devices → OLTs → Add OLT and fill in:

• Parent router — the router the OLT is connected behind.
• Name and Brand (e.g. V.SOL).
• OLT LAN IP — the OLT's address on the router's local network.
• OLT SNMP port — the port the OLT listens on for SNMP. Defaults to 161.
• SNMP community — a memorable value is generated for you (e.g. shimmeringbrain). You'll configure the same value on the OLT. Use “Generate a new community” to change it.
• Public IP (optional) — only if the OLT is directly reachable on a public address. Add :port if it's published on a non-standard port.

Step 2 — Allow ISPMan to reach the OLT

When the OLT sits behind a managed router, ISPMan needs the router to forward monitoring traffic to it. Open the OLT's page in ISPMan — under “Router command” you'll find a ready-to-run command tailored to this OLT.

1. Copy the command from the OLT page.
2. Paste it into the router's terminal.

Step 3 — Enable SNMP on the OLT

1. Log into the OLT's web/CLI and open the SNMP settings.
2. Enable SNMP v1/v2c and make sure the agent listens on the SNMP port you set in ISPMan (default 161).
3. Under the Community table, add a Read-Only community whose name exactly matches the ISPMan community (e.g. shimmeringbrain).
4. Permit SNMP access from the router's subnet. Most OLTs have an access-control / firewall list that limits who may query SNMP. Add a rule that permits SNMP from the /24 subnet of your router's management IP (shown on the OLT's page in ISPMan). For a router whose management IP is 10.121.x.x, permit the whole 10.121.0.0/24.

Step 4 — Verify

1. On the OLT's page, click Poll now.
2. On success you'll see system info, PON ports (with ONU counts), the ONU list, VLANs, and metric charts populate.
3. If it fails, the message tells you why — most often the community doesn't match, the router command hasn't been applied, or SNMP isn't enabled/allowed on the OLT.