[LARTC] DGD patch not detecting dead gateway

[Manish Kathuria]

On 1/20/07, Grant Taylor <gtaylor at riverviewtech.net> wrote:
> On 01/19/07 12:45, Manish Kathuria wrote:
> > My experience has been mixed. The patch worked very well in many cases
> > but in some it worked only if the first hop gateway was down and not
> > any of the subsequent hops. So as you mentioned its happening since it
> > can ping the switch / modem, it thinks the link is good. You can make
> > a script which will keep on running in the background and check it the
> > links are up or not and if any of the links is down, it can change the
> > default route and provide a failover.
>
> I have been tasked with writing such a script.  In my scenario, I'm
> taking it a bit further though.  I am planing on having my script test
> the actual service that I'm trying to connect to.  I.e. connect to port
> 80 and request a page.  I'm having to go this route because I've had
> sporadic MTU issues in one of our (primary) paths.  The provider is
> suppose to be repairing the problem, however I need a solution before
> that can happen.

The method I have adopted is to use a shell script which pings a
popular remote site 's IP (for example www.yahoo.com or
www.google.com) through each of the interfaces every 10 seconds. The
default multipath route is replaced by a single default gateway if
reply is not received for 4 consecutive tries from one of the links.
This is to avoid very frequent failovers. However, the link is treated
as live as soon as a  ping reply is received and the multipath route
is activated.

-- 
Manish Kathuria
Tux Technologies
http://www.tuxtechnologies.co.in/