Polling Interval: Network monitoring, SNMP and home-lab notes

Polling Interval is about the quiet part of running a network: knowing it is healthy before anyone has to ask. We write about SNMP and syslog, polling and alerting, uptime maths, open-source monitoring tools, home labs, and the careers built on keeping links green.

Despite the name, nothing here assumes a five-minute poll is sacred. Every guide is vendor-neutral where it can be, every command is something you can paste into a terminal, and every number is one you can check.

Start with the field manual

Nineteen chapters, from what a monitoring system does to writing your own checks:

• Basics: Introduction: what an NMS does and the vocabulary · Installing: sizing, the software stack and first steps · Data flow: raw input, events, consolidation, alarms, actions · Hosts: naming, groups, maps and auto-discovery · What to monitor: a catalog of check types
• Collecting data: Polling: pollers, intervals, timeouts, GETBULK and poller load · SNMP traps and informs, snmptrapd setup and testing · External inputs: traps, syslog, scripts and webhooks · Syslog lines to events with regular expressions
• Events and alerting: Events, alarms, severities and acknowledgement · Event filters and saved views for the console · Triggers, actions, escalation and dependencies
• Running the system: Using the console: status, acks, graphs, handover · Day-to-day administration: reports, cleanup, backups · Users, customers and who sees what · Satellites: polling from more than one place · Troubleshooting handbook: errors and fixes
• Extending: Worked example: graph ICMP messages over SNMP · Writing your own checks and pollers

Tools on the bench

• IPv4 subnet calculator: network, broadcast, usable range, mask and wildcard for any CIDR block, plus a split into smaller subnets
• SNMP counter to bit rate: two octet-counter readings to bits per second and utilization, with 32-bit wrap handling
• Uptime and SLA calculator: allowed downtime for any availability target, achieved uptime from an outage log, and serial or parallel paths
• Transfer time and bandwidth: how long a file or backup takes over a given link, and the link a deadline needs
• PoE budget calculator: power for access points, cameras and phones against a switch PoE budget, with headroom

Also here

• What a network monitoring system should do
• What useful monitoring screens show
• Free and open-source monitoring software worth downloading
• Help: getting unstuck with network monitoring
• Every article in the knowledge base