References > Template Reference > ISC DHCP Server (Linux)

ISC DHCP Server (Linux)

This 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 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, you should correct all components in the first line of the Script Body field (#!/usr/bin/perl), or you can create a symbolic link to Perl (refer to your documentation for the ln command).

You can find where Perl is installed by using the following command: which perl

Credentials

Root credentials on the target server.

Tested on CentOS 5.5 and ISC DHCP 3.0.5 version.

Monitored Components

For details on monitors, see SAM Component Monitor Types.

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 – This component returns the number of queries, which the client broadcasts to locate available servers.
  • Offer – This component returns the number of DHCP server responses to Discovery queries offering, with configuration information.
  • Request – This component returns 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 – This component returns the server's response to the client Request queries containing configuration parameters, including committed network address.
  • Nak – This component returns 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 – This component returns the number of clients’ queries indicating network address is already in use.
  • Release – This component returns the number of clients’ queries relinquishing network address and cancelling the remaining lease.
  • Inform – This component returns 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, there may be problems with SNMP configuration or the Dhcpd service has stopped.