Documentation forServer & Application Monitor
Monitoring your applications and environment is a key capability of SolarWinds Observability Self-Hosted (formerly Hybrid Cloud Observability) and is available in the Essentials edition. Server & Application Monitor (SAM) is also available in a standalone module.

ISC DHCP Server (Linux)

This SAM application monitor template assesses the performance of the ISC DHCP service on Linux machines. It uses Perl script and an SNMP process monitor for monitoring the performance of queries.

Prerequisites

SSH and Perl are installed on the target server. SNMP installed on the target server and permission to monitor dhcpd processes.

If Perl is installed in a location different from /usr/bin/perl, correct all components in the first line of the Script Body field (#!/usr/bin/perl), or create a symbolic link to Perl with a ln command).

To locate the Perl installation, run: which perl

Credentials

Root credentials on the target server.

Tested on CentOS 5.5 and ISC DHCP 3.0.5 version.

Component monitors

You need to set thresholds for counters according to your environment. It is recommended to monitor counters for some length of time to understand potential value ranges and then set the thresholds accordingly.

Queries Rate per Sec

This monitor returns the rates per second of different queries. All rates are calculated as the number of specific queries for 20 seconds and then divided by 20. Information about DHCP queries are taken from the /var/log/messages file. It is possible that scripts will return non-integer values. Returned values are as follows:

  • Discovery – The number of queries, which the client broadcasts to locate available servers.
  • Offer – The number of DHCP server responses to Discovery queries offering, with configuration information.
  • Request – The number of clients’ responses to the server Offer packets, containing the following:
    • Requesting offered parameters from one server and implicitly declining offers from all others
    • Confirming correctness of previously allocated address after, (e.g., system reboot)
    • Extending the lease on a particular network address
  • Ack – The server's response to the client Request queries containing configuration parameters, including committed network address.
  • Nak – The server's response to the client Request queries indicating the client's notion of the network address is incorrect (e.g., client has moved to new subnet) or client's lease has expired.
  • Decline – The number of clients’ queries indicating network address is already in use.
  • Release – The number of clients’ queries relinquishing network address and canceling the remaining lease.
  • Inform – The number of clients’ queries where the client is asking only for local configuration parameters (client already has externally configured network address).

SNMP Process Monitor: Dhcpd

This component returns CPU and memory usage of the Dhcpd daemon.

If this counter is unavailable, check the SNMP configuration and make sure the Dhcpd service is running.