Advanced Settings For Route Failover - D-Link DFL-260E User Manual

4.2.5. Advanced Settings for Route
Failover
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.
HTTP Parameters
If the HTTP polling method is selected then two further parameters can be entered:
• Request URL
The URL which is to be requested.
• Expected Response
The text that is expected back from querying the URL.
Testing for a specific response text provides the possibility of testing if an application is offline.
If, for example, a web page response from a server can indicate if a specific database is
operational with text such as "Database OK", then the absence of that response can indicate that
the server is operational but the application is offline.
A Known Issue When No External Route is Specified
With connections to an Internet ISP, an external network route should always be specified. This
external route specifies on which interface the network which exists between the NetDefend
Firewall and the ISP can be found. If only an all-nets route is specified to the ISP's gateway, route
failover may, depending on the connected equipment, not function as expected.
This issue rarely occurs but the reason why it occurs is that ARP queries arriving on a disabled route
will be ignored.

4.2.5. Advanced Settings for Route Failover

The following NetDefendOS advanced settings are available for route failover:
Iface poll interval
The time in milliseconds between polling for interface failure.
Default: 500
ARP poll interval
The time in milliseconds between ARP-lookup of hosts. This may be overridden in individual
routes.
Default: 1000
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Chapter 4. Routing