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Re: Automatic ISP failover if connection fails

On Fri, 8 Oct 2004 12:05:56 -0700 (PDT), Mike Mestnik
<cheako911@yahoo.com> wrote:
> --- Albert Ulmer <jayaeu@gmail.com> wrote:
> > OK, sounds reasonable. Can this scheme be adapted to a scenario where
> > 1 NIC (no pppd) and 1 ISDN-card are involved? Putting
> > up-/down-statements into the NIC-setup won't do much good, as the
> > NIC-link doesn't go down, even when the connection on the WAN-side is
> > lost.
> > 
> What happens is the routing code detects that the metric 0 path isn't
> working and it starts using the metric 1 part.  The thing that may be
> tricky for you, I don't know ISDN only NICs, is that you must keep the
> interface bound to an IP and have routes(that have a higher metric)
> attched to it.  This means that the interface has to be "ifconfig xxxy
> up", but maby not dialed and working.

The ippp0 interfaces pretty much behaves like a normal eth-interface.
I should be able to assign a static IP-address for routing purposes,
albeit using a virtual ippp0.0 interfaces if necessary.

> > Is there a way to alter the metric of an interface based on RTT of the
> > ISP-router on the other side of the link? I guess this would solve
> > part of the problem....
> > 
> That's what metric is, it's the admins perseption of what routes are
> better then others.  You could base this only on RTT, but that may be
> narrow minded.

That would basically be what I want: If the RTT goes up, try the
alternative uplink. It may be narrow minded, but it would certainly
get the job done. ;)

Best regards,

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