Introduction
After installing Nagios on the Master server and NRPE on the Slave server, open the Nagios Web UI to monitor hosts and services in real time.
Tactical Status Overview
Provides a high-level overview of all hosts and services. Displays whether hosts are UP, DOWN, or UNREACHABLE.
- DOWN: Host is confirmed offline or not responding.
- UNREACHABLE: Nagios cannot determine status due to parent/network issue.
Map Page (Network View)
Visual representation of your monitored infrastructure. Shows how hosts are connected and highlights issues.
- Topological view of infrastructure
- Displays host groups and parent/child relationships
- Status color codes:
- Green → UP / OK
- Yellow → WARNING
- Red → DOWN / CRITICAL
- Gray → UNREACHABLE / PENDING
Host Page
Displays all monitored hosts with real-time status information.
| Column | Description |
|---|---|
| Host Name / Alias | Name of host and optional friendly alias |
| Status | UP (green), DOWN (red), UNREACHABLE (gray) |
| Last Check | Timestamp of last check |
| Duration / Uptime | Time host has been in current state |
| Attempt / Hard State | Current attempt vs max attempts; HARD or SOFT state |
| Last State Change | When host status last changed |
| Notifications | Last notification sent & total notifications |
| Scheduled Downtime | Shows if host is in planned maintenance |
| Flap Detection | Indicates frequent state changes |
Service Page
Displays services being monitored, grouped by host. Shows real-time service states:
- OK
- WARNING
- CRITICAL
- UNKNOWN
Host Groups & Service Groups
- Organize multiple hosts under one group
- Apply common notifications or checks
- Useful for large infrastructures
- Simplifies dashboards and reporting
Problems Page
Displays all hosts and services currently in non-OK state:
- WARNING
- CRITICAL
- UNKNOWN
- DOWN
- UNREACHABLE
Navigation Summary
- Host Page → Overview of host status
- Service Page → Overview of service status
- Network Page → Connectivity & dependencies