Avaya G250 Administration page 235

Modem dial backup uses the G250/G350's backup interface functionality to activate the Dialer
interface for modem dial backup when the primary interface fails and to deactivate the Dialer
interface when the primary interface is up again. Currently, modem dial backup does not
support such features as Dial On Demand Routing (DDR), callbacks, or RAS. Modem dial
backup cannot receive backup calls. For more information about backup interfaces, see
interfaces on page 232.
Note:
You can only backup one interface with modem dialer backup.
Note:
Using the G250/G350's backup interface functionality, you can designate the Dialer interface as
the backup for the main WAN link. However, this method is not always available, since an 'up'
WAN link status does not ensure connectivity, and the main WAN link may not even be directly
connected to the G250/G350.
The workaround is to use the G250/G350's object tracking feature to verify connectivity to the
primary MGC using Respond Time Reports (RTRs) and object trackers. Configure object
tracking to change the state of the Loopback interface accordingly, and configure the Dialer
interface as a backup to the Loopback interface. For more information about object tracking,
see Object tracking on page 256.
Modem dial backup uses a modem connected directly to the G250/G350's USB or console port.
The modem can also be used to access the G250/G350 CLI from a remote location. The
modem cannot do both at the same time. For information about remote access to the G250/
G350 via modem, see
Finally, IP routing must be configured so that traffic to and from the site uses the Dialer interface
when the primary interface is down. The Dialer interface can work both with static and dynamic
routing (OSPF and RIP). Note that the latter mandates the use of unnumbered IP interfaces.
For information about unnumbered IP interfaces, see
page 406.
Note:
Modem dial backup has complex interactions with other configuration modules
Note:
within the G250/G350 and on your network. Before configuring modem
dial-backup, Avaya recommends reading Application Note - VoIP Network
Resiliency. This document discusses the issues of network design for maximum
resiliency, capacity planning for optimum performance, configuration options for
network devices, strategies for implementing routing across the network, and
security concerns. Based on your existing network design, several redundancy
scenarios featuring modem dial backup are available. See
interactions with other features
features required for an effective backup scenario for your VoIP installation.
Note:
Modem dial backup does not support backup dial-ins or callbacks. Some backup
Note:
configurations require the remote host to receive a request for connection,
acknowledge, end the connection, and dial back the requester. This configuration
is not supported.
Accessing the CLI via modem
on page 240 for brief discussions of the various
on page 37.
Configuring unnumbered IP interfaces
Modem dial backup
Issue 3 February 2007
Modem dial backup
Backup
on
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