[LARTC] dead gateway detection in linux

[Madhuri Patwardhan <madhuri@cc.iitb.ac.in>]

Hi,

Few questions:

1] How does dead gateway detection happen in Linux?

2] I am using multipath default routes and I want the kernel to detect
when a particular default route is down and stop using it. I would also
like the kernel to detect when that particular default route is up and
start reusing it. From the reading that I have done so far I realized
there are two options.
a] One option is to use Juliano's patches
(http://www.ssi.bg/~ja/nano.txt). From what I understand Juliano's
patches provide following. The patches let a static route be marked as
'dead' when it goes down. Also it detects that when the route is up and
starts using it. However, it requires that we use NAT. I do not want to
use NAT. In that case will his patches work for me?
Another question regarding his patches is how does kernel detect when a
route is dead?

b] second option is put together a simple script which pings and find
out when routes are dead and changes the multipath default routes
accordingly. That is what I am doing now. I would like to know if there
is a better option.

I would appreciate if more pointers/information/options are provided for
failover mechanism in mutipath default routes.


Thanks,

Madhuri

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