[plug] ADSL failover

[Colin Muller]

On Sun, Aug 19, 2001 at 09:55:06PM +0800, Glen Lewis wrote:

> Its always a bit disappointing when you can't compete in every
> market.  iiNet has a policy of only entering markets which it can make an
> iota of profit - the home aDSL market is not one of those.  We will
> continue to try to provide a competative service in those markets we can -
> in this case the business customers.

Having just spent two days involuntarily off-line (I take back
*everything* I said here last week about failover modem backup being
unnecessary with iiNet's ADSL service), might I suggest that a
profitable service to offer would be along the lines of "for a fee of
$50/$100/$whatever, we'll guarantee to have you back on line it within
4 hours, and no excuses". I'm sure there are others who, like me,
really need to reduce downtime and would pay for such a service, and for
the pleasure of NOT being told "it's Sunday and I don't have the key
to the modem store" or having the blame for the delay shifted onto
Telstra - iiNet and Telstra could both make money out of extra fees
like this.

Simon, what you probably want for failover is to ping/traceroute via
the eth-whataver port (the default route one for the ADSL) to a
specific machine every couple of minutes (using cron, I guess) and
parse the result.  If it indicates failure, delete the default route,
substitute a more slimly-masked route via that same Ethernet port to
the machine you're (trac|ping)ing, and fire up the ppp connection with
a default route through ppp0. Keep (trac|ping)ing the other one via the
ADSL eth port, and when it comes back up, kill the ppp link and
reinstate the default route via the ADSL connection. All not too hard
to automate. Note that this is useless for incoming traffic to a fixed
IP - that would require routing co-operation from your ISP. It would
work well for Web browsing etc, though.

Colin