net access failover

[Barney Wolff]

On Sat, Dec 27, 2003 at 03:57:16PM -0500, mark abrams wrote:
> 
> I have a cable modem and and a dsl connction to my machine. I would like to 
> use the cable modem as my default connection and automatically fail-over to 
> the dsl connection if/when the cable modem goes down.
> 
> Can routed(8) do this ? If so how? And is there a better way ?

I guess this should be a FAQ.  For something that can be adapted to
do what you want, see http://www.databus.com/dslsec.tgz .

routed won't do it because (unlike real multihoming) your address on
the two networks is different and the ISPs are not sending you any
routing protocol packets.  A simpleminded ping of the cable ISP's
router, and changing the default route when it goes away and comes back,
should work fine.  NATing adds a little to the effort, if you do it.
Existing connections will not survive a transition, but that's usually
not a big deal.

-- 
Barney Wolff         http://www.databus.com/bwresume.pdf
I'm available by contract or FT, in the NYC metro area or via the 'Net.