multihomed is a script that can detect when your
primary Internet uplink goes down and switch to a
backup uplink. It's smarter than many similar
scripts: it continuously pings several hosts
around the Internet using both uplinks, and elects
the best one as primary. You can define the
priority with which uplinks are tried. This can be
very useful if you have a per-traffic contract on
one of your uplinks and a flat-traffic contract on
another one: you can configure multihomed to use
the per-traffic uplink only if the other one is
not working. It runs as a daemon, and you can
define the interval between consecutive checks. It
can detect failures in your ISP's uplinks too; by
checking multiple remote hosts around the
Internet, you can tell if your ISP is fully
working or not. This is much more reliable than
simply pinging a single server or (worse) your
default router. It is very flexible: you can
easily customize the commands to execute whenever
one of the links goes down.
