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SONICWALL SONICOS STANDARD 3.0 ADMINISTRATOR’S GUIDE
C
HAPTER
19:
Configuring Modem Failover
Before you configure your Modem Failover Settings, create your dialup profiles in the Modem Profile
Configuration window, which you access from the Modem > Dialup Profiles page.
S
Alert: The SonicWALL security appliance modem can only dial out. Dialling into the internal modem is
not supported. However, an external modem can be connected to the Console port for remotely
accessing the SonicWALL security appliance for out-of-band support.
Configuring Modem Failover
Use the following instructions to configure the Failover Settings:
1
Select Enable WAN Failover.
2
Select Enable Pre-empt Mode if you want the primary WAN Ethernet interface to take over from
the secondary modem WAN interface when it becomes active after a failure. If you do not enable
Pre-empt Mode, the secondary WAN modem interface remains active as the WAN interface until
you click Disconnect.
3
Select Enable Probing. Probing for WAN connectivity occurs over the Ethernet connection, the
dial-up connection, or both. When probing is disabled on the Ethernet link, the SonicWALL security
appliance only performs link detection. If the Ethernet connection is lost for a duration of 5-9
seconds, the SonicWALL security appliance considers the Ethernet connection to be unavailable.
If the Ethernet link is lost for 0-4 seconds, the SonicWALL security appliance does not consider the
connection to be lost. If you are swapping cables quickly, unnecessary WAN failover does not
occur on the SonicWALL security appliance. If probing is enabled and the cable is unplugged, the
5-9 seconds link detection does not occur. Instead, the probing rules apply to the connection using
the parameters configured for Probe Interval (seconds) and Failover Trigger Level (missed
probes) settings. If probing is enabled on dialup, the dialup connection is terminated and re-
established when probing fails over the modem.
4
Select an option from the Probe through menu. Select Ethernet Only to probe the Ethernet WAN
connection and failover to the modem when the connection is lost. Select Modem Only to probe a
dial-up connection and have the modem redial when the dial-up connection is lost. Select Modem
and Ethernet to enable both types of probing on the SP.
5
Enter the IP address for the probe target in the Probe Target (IP Address) field. The Probe IP
address is a static IP address on the WAN. If this field is left blank, or 0.0.0.0 is entered as the
address, the Probe Target is the WAN Gateway IP address.
9
Tip: The probe is a ping sent to the IP address and is used, along with the response, as a method of
determining Internet connectivity.
6
Select ICMP Probing or TCP Probing from the Probe Type options. If you select TCP Probing,
enter the TCP port number in the TCP port field.
7
In the Probe Interval (seconds) field, enter the amount of time between probes to the Probe
Target. The default value is 5 seconds. To deactivate the Probe Detection feature, enter 0 as the
value. In this case, the WAN failover only occurs when loss of the physical WAN Ethernet
connection occurs on the SonicWALL security appliance.
8
Enter the number of missed probes required for the WAN failover to occur in the Failover Trigger
Level (missed probes) field.
9
Enter a value for the number of successful probes required to reactivate the primary connection in
the Successful Probes to Reactivate Primary field. The default value is five (5). By requiring a
number of successful probes before the SonicWALL security appliance returns to its primary
connection, you can prevent the SonicWALL security appliance from returning to the primary
connection before the primary connection becomes stable.
10
Click Apply for the settings to take effect on the SonicWALL security appliance.