[LARTC] 2 default gw in redhat 6.2

[Arthur van Leeuwen arthurvl@sci.kun.nl]

<PRE>On Fri, 2 Feb 2001, Rene 'Lynx' Pfeiffer wrote:

&gt;<i> On Thu, 1 Feb 2001, Arthur van Leeuwen wrote:
</I>&gt;<i>
</I>&gt;<i> &gt; On Thu, 1 Feb 2001, Rene 'Lynx' Pfeiffer wrote:
</I>&gt;<i> &gt;
</I>&gt;<i> &gt; &gt; On Thu, 1 Feb 2001, Arthur van Leeuwen wrote:
</I>&gt;<i> &gt; &gt;
</I>&gt;<i> &gt; &gt; &gt; On Thu, 1 Feb 2001, bert hubert wrote:
</I>&gt;<i> &gt; &gt; &gt;
</I>&gt;<i> &gt; &gt; &gt; &gt; Linux is supposed to have something called 'dead gateway detection'
</I>&gt;<i> &gt; &gt; &gt;
</I>&gt;<i> &gt; &gt; &gt; Which it doesn't use when there's a multipath default route. Now, that isn't
</I>&gt;<i> &gt; &gt; &gt; technically the case here, so that shouldn't be the problem here.
</I>&gt;<i> &gt; &gt;
</I>&gt;<i> &gt; &gt; Does this mean that Linux automatically detects a failed default
</I>&gt;<i> &gt; &gt; route and takes the second one if I configure two default routes?
</I>&gt;<i> &gt;
</I>&gt;<i> &gt; No, it means the exact opposite. If you configure two default routes
</I>&gt;<i> &gt; Linux will randomly multiplex outgoing connections over the two routes.
</I>&gt;<i>
</I>&gt;<i> This is exactly the problem I am having. I am trying to set up a spare default
</I>&gt;<i> route in case the primary route is down. The router in question is a Linux
</I>&gt;<i> machine having access to three upstream connections and to the DMZ. I do not
</I>&gt;<i> want to have routing daemons on the box, I simply want to change the default
</I>&gt;<i> route in case the primary connection (which supplies the LAN behind the DMZ)
</I>&gt;<i> is down.
</I>
&gt;<i> The only thing I have come up so far (I do not want to have fancy things like
</I>&gt;<i> zebra, routed or gated on this machine) is a Perl script that measures the
</I>&gt;<i> connectivity and takes action if it detects that the route is down.
</I>
&gt;<i> Does anyone have a better idea? (I am willing to to a nice and tidy ASCIIgram
</I>&gt;<i> if you like ;-)
</I>
Nope. Polling for connectivity is what you're stuck with doing, unless you
want to do some kernel hacking.

Doei, Arthur. (Who is thinking about actually doing the latter... it's
               *useful*, in more cases than one)

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</PRE>