D-Link DFL-210 - NetDefend - Security Appliance, User Manual

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Specifying Hosts
For each host specified for host monitoring there are a number of property parameters that should be
set:
• Method
The method by which the host is to be polled. This can be one of:
• ICMP - ICMP "Ping" polling. An IP address must be specified for this.
• TCP - A TCP connection is established to and then disconnected from the host. An IP
address must be specified for this.
• HTTP - A normal HTTP server request using a URL. A URL must be specified for this as
well as a text string which is the beginning (or complete) text of a valid response. If no text
is specified, any response from the server will be valid.
• IP Address
The IP address of the host when using the ICMP or TCP option.
• Port Number
The port number for polling when using the TCP option.
• Interval
The interval in milliseconds between polling attempts. The default setting is 10,000 and the
minimum value allowed is 100 ms.
• Sample
The number of polling attempts used as a sample size for calculating the Percentage Loss and
the Average Latency. This value cannot be less than 1.
• Maximum Failed Poll Attempts
The maximum permissible number of polling attempts that fail. If this number is exceeded then
the host is considered unreachable.
• Max Average Latency
The maximum number of milliseconds allowable between a poll request and the response. If this
threshold is exceeded then the host is considered unreachable. Average Latency is calculated by
averaging the response times from the host. If a polling attempt receives no response then it is
not included in the averaging calculation.
The Reachability Required option
An important option that can be enabled for a host is the Reachability Required option. When this
is selected, the host must be determined as accessible in order for that route to be considered to be
functioning. Even if other hosts are accessible, this option says that the accessibility of a host with
this option set is mandatory.
Where multiple hosts are specified for host monitoring, more than one of them could have
Reachability Required enabled. If NetDefendOS determines that any host with this option enabled
is not reachable, Route Failover is initiated.
4.2.4. Host Monitoring for Route
Failover Chapter 4. Routing
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