location. The modem cannot do both at the same time. For information about remote access
to the Branch Gateway via modem, see CLI access using modems on page 31.
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
Unnumbered IP interfaces on
page 426.
Note:
Modem dial backup has complex interactions with other configuration modules within the
Branch Gateway 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
Modem dial backup
interactions with other features on page 264 for brief discussions of the various 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
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.
Related topics:
Typical installations on page 260
Prerequisites for configuring modem dial backup on page 261
Configuring modem dial backup on page 261
Modem dial backup interactions with other features on page 264
Configuration example on page 266
Modem dial backup maintenance on page 270
Typical installations
The Branch Gateways were designed for small branch offices of a larger enterprise.
Consequently, the same RAS may serve many branch offices, and, therefore, many Branch
Gateways. A reasonable assumption is that not all branch offices would need modem dial
backup at the same time. Therefore, the ratio of modem channels at the RAS to Branch
Gateways at branch offices can be less than 1:1. There are several practical ways to configure
the RAS server for use with modem dial backup Dialer interfaces:
• The RAS can assign an IP address to the calling Branch Gateway. This requires the RAS
to identify the call gateway using the PAP/CHAP username, and install an appropriate
WAN interfaces
260 Administering Avaya G430 Branch Gateway October 2013
Comments? infodev@avaya.com
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