Installation guide

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Failover/load balancing
Failover
The failover principle is to have multiple Internet service providers, and let your gateway device handle the
connections for you automatically, depending on needs and availability of service.
The problem
We are becoming increasingly dependent on the Internet. Email is becoming the mainstream
communications medium, not only replacing traditional postal mail but also phone communications to some
degree. Financial transactions (online banking and shopping) is gaining importance, as is online information
access of any kind.
Especially in medical practice, we expect online services (like pathology result downloads) to be accessible
around the clock. However, often this depends on access to developing broadband infrastructure and types
of online services offered by the many vendors involved.
In cases where you absolutely rely on broadband connectivity (as in hosting our medical records with an
Application Service Provider (ASP) or via VPN at a branch surgery) you cannot afford to depend on a single
unreliable service. Even with uptime of 99.9%, you still have one working day per year when the service will
not be available from this provider, and virtually no Australian service provider can even go as far as
providing a 99.9% uptime guarantee.
The solution
The solution is not putting all your eggs into a single basket. Choose one Internet access service as your
primary service, but always have at least one more service that uses different infrastructure as backup.
Examples of services using different infrastructures:
•(A)DSL.
• phone line dial up – strictly speaking it uses the same infrastructure as (A)DSL (namely your
phone line), but the most frequent cause of failure of the (A)DSL system will not disrupt
phone services on the same line at the same time.
• cable Internet.
• two way Satellite Internet (VSAT).
• wireless Internet.
Figure 9: accessing two different ISPs via a single router device with 2 WAN ports