Product specifications

Efficient Networks
®
Router family
Command Line Interface Guide
Chapter 6: Connection Management
Efficient Networks
®
Page 6-7
Dial Backup
The Dial Backup capability provides a backup asynchronous modem connection to
the Internet when the default DSL link goes down. If your router model is equipped
with an internal modem and the feature key is present, the backup connection uses
the internal modem; otherwise the backup connection uses an external modem. The
modem connection is provided through the MGMT (console) port. In this case, the
console port is used as a serial port and must be connected to an external modem.
NOTE:
The Dial Backup feature is effective using either V.90 or ISDN modems.
Dial Backup is intended for customers with critical applications for which continuous
Internet access is vital. If the DSL link for those applications goes down, the router
can automatically switch their traffic to the asynchronous modem. Later, after
determining that the DSL link is, once again, up and stable, the router automatically
switches the modem traffic back to the DSL link.
This feature may also be useful for a customer whose DSL line is not yet installed.
The router can begin providing service through an asynchronous modem and later
automatically switch to the DSL link when it becomes available.
Dial Backup can be used with a VoDSL (voice over DSL) router. However, when data
traffic is switched to the backup modem or restored to the DSL connection, all voice
calls are terminated.
Dial Backup with a Tunnel
Dial Backup works with L2TP and IPSec tunneled connections. However, an IPSec
tunnel from the backup interface must use IKE aggressive mode, not IKE main mode,
because, it is assumed that the ISP assigns an IP address to the backup interface
dynamically (see “Main Mode and Aggressive Mode” on page 5-54.)
You may wish to restrict an L2TP tunnel or IPSec tunnel to only the primary interface
or only the backup interface:
If you do not want tunnel traffic to go through the backup asynchronous modem, you
should restrict the tunnel to use only the primary interface. With this restriction in
place, if the primary interface fails, the tunnel is terminated, and it is not re-established
with the backup interface.
Or, you might want a tunnel to be established only when the asynchronous modem is
being used. In this case, you would restrict the tunnel to the backup interface only.
To set either restriction for an L2TP tunnel, use the l2tp set wanif command. On the
command, you specify the remote name that the tunnel is restricted to and the tunnel
name. To restrict the tunnel to the backup interface, specify the remote name that you
created for the dialup parameters as described in “Specifying Modem Parameters” on
page 6-14.