[Cerowrt-devel] dealing with soft default gateway failures

[Dave Taht]

I have a couple situations where the default gw fails for some reason
or another and I would like to sanely fail over to another router. In
two case, the dsl modem in place periodically loses connectivity and
should fail over to the cable modem in place...

and in another case I had plugged in a cable modem that supplied a
default route but did not actually have connectivity to the internet
itself, but have multiple cable modems on the same network each with a
babel interface to them, supplying default routes where appropriate.

I filed a request for babel-pinger here, but it doesnt quite do what I
want. I would like something more responsive.

https://github.com/openwrt-routing/packages/issues/65

Rather than constantly pinging at a slow rate, having an iptables rule
that looked for ICMP unreachable messages and fired up a ¨checker¨
process to see if basic connectivity had been lost (both for ipv4 and
ipv6) seems like a solution that is faster and lighter weight and more
robust.

Instead of trusting the default dhcp route, do something to check that
the path is good, first, instead.

-- 
Dave Täht

thttp://www.bufferbloat.net/projects/bloat/wiki/Upcoming_Talks