Fail Detection

It is important for LSNAT to know whether a real server can provide the requested service. There are three methods supported to determine the state of a real server, server ports, and its applications:

Fail detection methods are configured within probes using the tracked object manager facility. Probe creation and configuration is detailed, along with fail detection method details in Tracked Object Manager Configuration.

ICMP ping probe monitoring of a real server occurs by default, using the predefined ICMP probe $slb_default. See Preset Default ICMP Probes for preset default ICMP probe details.

LSNAT server load balancing supports the assigning of up to two probes per server: an ICMP ping and a UDP or TCP probe that can be configured for port verification and optionally for application content verification. Probes are assigned to a real server configuration using the faildetect probe command in real server configuration mode. When assigning a probe to a real server, specify probe one or two, and the name of the probe. The $slb_default default ICMP ping probe is auto-assigned to probe one, whenever probe one is not configured with an administratively created probe.

The probe type setting allows you to set whether configured probes are active or inactive for a server context. The probe type setting does not change the probe configuration. When probe type is set to probe, the probe configuration for the server context is active; probes are sent to the server in accordance with the configured settings. When probe type is set to none, the probe configuration is inactive; no probes are sent for the server context, and the real server is set to UP. The default probe type is probe. Use the probe type command in real server configuration mode to set the probe type for the server context.

In a server configuration context, probe configuration can be reset to factory default values by resetting fail detection for that server context. Resetting fail detection in a server configuration context:

Any preexisting probe is overwritten when assigning a probe.

This example shows how to: