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Introduction Internet-based WAN Backup Solutions using NetVanta
2 Copyright © 2005 ADTRAN, Inc. 61200890L1-29.4A
Introduction
WAN communication links are traditionally the weakest component in computer networking. Unlike LAN
components, which are typically in the owner's direct physical and administrative control, the facilities that
make up the WAN link belong to and are controlled by a third party. These facilities also cover wide
geographic areas, making them more susceptible to physical harm. Such characteristics make WAN links
the single largest contributor to network downtime.
When the WAN link is critical to a network's operation, it is wise to design towards WAN resiliency. In
some cases, the volume and criticality of the WAN might dictate the need to completely duplicate the
WAN with redundant and independent facilities. The cost of this solution can be quite high, so the benefit
must be carefully weighed.
Another common solution, especially in large hub and spoke networks, is to use dial backup around the
WAN provider. In this solution, should a spoke lose its WAN connectivity to the hub, it will place a call to
a dial-up server located at the hub, completely bypassing the WAN. While this is a well known solution
that has been used for many years, the cost of dial-up server ownership, maintenance, and long distance
toll charges can be quite high.
The Internet as an Alternative
Using the stateful inspection firewall and powerful IPSec VPN capabilities provided in the NetVanta router
product line, the Internet can be a useful and low cost alternative for WAN connectivity -- as a backup or
even as a primary connection. Internet use eliminates the dial-up server and its ownership and maintenance
expenses, in effect outsourcing management of the modem bank to local ISPs at each location. It also
eliminates toll charges since each location can connect via a local ISP. A site can remain connected
indefinitely for a flat fee in many areas, incurring no toll charges.
Following are descriptions and detailed examples of several Internet-based backup solutions. These
solutions have been tested with AOS Version 8.0.22E.
Note that detailed firewall design and VPN design are dependent on each network's unique requirements.
The examples shown here are simpified to focus on the mechanics of using a primary and backup
connection.
Also note that in these examples, the NetVanta is the remote site router. A NetVanta or a third party device
can be used as the central router and the central FW/VPN gateway.