Nokia ISAM GPON Checkmk Plugin

Checkmk SNMP plugin for monitoring Nokia ISAM GPON equipment.

Features

Check	Services	Data
Linecard	Per-slot availability	Planned/actual type, serial, availability state
GPON	Per-port status	Admin/oper status, SFP optics, traffic stats

GPON Metrics

• SFP optics: Tx/Rx power (dBm), bias current (A), voltage (V), temperature (C)
• Traffic: Tx/Rx bytes (unicast, multicast, broadcast, total, drops)
• Utilization: Tx/Rx utilization percentages
• Other: Active ONTs, DBA congestion time

SNMP Detection

Detects Nokia ISAM devices where sysDescr contains NOKIA ISAM.

Polling and Caching

The plugin provides two SNMP sections:

Section	Contents	Cost per host	Cache it?
oposs_isam_gpon	PM traffic counters	~1 s	no — must be fetched every run
oposs_isam_gpon_info	SFP optics, descriptions, interface status	~11 s	yes, at 300 s

The optics table is read from the SFP hardware on demand — about 23 ms per row against 5.8 ms for the counters — so it dominates the host's SNMP fetch. Splitting it out is what makes a short check interval affordable. Measured on a 16-port OLT, per 300 s of wall time:

Setup	SNMP per 300 s
300 s check interval (default)	18 s
60 s check interval, no caching	68 s (3.8x)
60 s check interval, _info cached at 300 s	22 s (1.2x)

The plugin works unchanged at the default interval. A 60 s interval mainly improves how faithfully bursty traffic is represented, because the counters are then differenced within one PM window instead of being read once per window.

To enable it, two rules in Checkmk:

1. Setup → Service monitoring rules → Service checks → "Normal check interval for service checks" — set 1 minute for these hosts. Scoping the rule to the service Check_MK$ is enough; that is the active check which drives the SNMP fetch.
2. Setup → Agents → SNMP rules → "Fetch intervals for SNMP sections" — add oposs_isam_gpon_info (and oposs_isam_linecard) at 300 s. Do not add oposs_isam_gpon. The internal name of this ruleset is still snmp_check_interval.

Install the package and activate before adding the rules, so the oposs_isam_gpon_info section exists when it is referenced. Setting the interval while an older, unsplit version is active is the 3.8x case.

Upgrading to 0.5.0

The traffic rate and utilization metrics were renamed and no translation maps the old names onto the new ones, so those graphs start empty. This is deliberate: every value they held was written by 0.2.0 through 0.4.0, whose rate conversion assumed a 900 s PM window where the device uses 300 s. That produced spikes far above the GPON line rate and under-reported steady traffic by roughly 6x, and filtering the spikes would leave a plausible- looking graph that is still wrong by that factor.

The SFP optics metrics, active-ONT count and DBA congestion time keep their names and their history.

Installation

MKP Package (recommended)

Download the latest .mkp file from the Releases page and install it:

mkp install oposs_isam_gpon-<version>.mkp

Manual Installation

Copy the plugin files into your Checkmk site:

local/lib/python3/cmk_addons/plugins/oposs_isam_gpon/
├── agent_based/
│   └── oposs_isam_gpon.py
├── checkman/
│   └── oposs_isam_gpon
└── graphing/
    ├── isam_gpon.py
    └── translations.py

License

GNU General Public License v3 - OETIKER+PARTNER AG. See LICENSE.

v3 rather than v2 because SLOT_TABLE and PORT_TABLE_NT in agent_based/oposs_isam_gpon.py are taken from LibreNMS, which is GPL v3; see the commit link in the source. GPL v3 code cannot be relicensed to v2.