Monitoring; The Link Monitor - D-Link DFL-1660 User Manual

2.4. Monitoring

2.4. Monitoring
The real-time performance of NetDefendOS can be monitored in a number of ways. They are:
• The NetDefendOS link monitor.
• Monitoring through an SNMP client.
• Hardware monitoring for specific hardware models.

2.4.1. The Link Monitor

Overview
The Link Monitor is a NetDefendOS feature that allows monitoring of the connectivity to one or
more IP addresses external to the NetDefend Firewall. This monitoring is done using standard ICMP
"Ping" requests and allows NetDefendOS to assess the availability of the network pathways to these
IP addresses. The administrator can select one of a number of actions to occur should a pathway
appear to be broken for some reason.
Link Monitor Actions
If sufficient replies are not received to link monitor polling, NetDefendOS makes the assumption
that the common link to those IP address is down and can then initiate one of 3 configurable actions:
• A NetDefendOS reconfigure.
• A High Availability (HA) cluster failover.
• An HA cluster failover followed by a NetDefendOS reconfigure.
The Link Monitor Reconfigure is Different
The reconfigure that can be triggered by the link monitor has one special aspect to it. The link
monitor reconfigure has the additional action of restarting all interfaces. This means that if there is a
problem related to a particular Ethernet NIC, perhaps due to overload, then this can be cleared by
interface initialization. This results in only a momentary delay in throughput while the reconfigure
takes place.
Link Monitor Uses
The Link Monitor is useful in two distinct scenarios:
• An external device develops an occasional problem with its link to the NetDefend Firewall and
the physical link needs to be renegotiated. Such problems can occur sometimes with some older
equipment such as ADSL Modems. For this scenario action 1. Reconfigure should be selected.
A reconfigure means that the NetDefendOS configuration will be reloaded. All connections and
states are saved but reloading means all traffic is suspended for a short period and all interface
Note: Link monitoring is not available on all NetDefend models
The link monitoring feature is only available with the D-Link NetDefend
DFL-1600, 1660, 2500, 2560 and 2560G.
Chapter 2. Management and Maintenance
72