[LARTC] interaction between different tables' default routes

[LARTC] interaction between different tables' default routes

[bert hubert]

On Wed, Feb 27, 2002 at 04:29:23PM +0530, suresh wrote:

> to forward request from another lan network it works fine
> but req from 172.16.1.0 does not work
> 
> if i remove 
> ip route del default via w.x.y.z dev eth1
> 
> its work well.
> 
> Did i leaveout anything in configuration?

I'm not sure about this. At one point I understood how this worked but I
don't anymore. There is something in the HOWTO about fallback routes. I
think there are people here who do understand the interaction between
different tables' default routes.

Regards,

bert

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Re: [LARTC] interaction between different tables' default routes

[Arthur van Leeuwen]

On Thu, 28 Feb 2002, bert hubert wrote:

> On Wed, Feb 27, 2002 at 04:29:23PM +0530, suresh wrote:
>
> > to forward request from another lan network it works fine
> > but req from 172.16.1.0 does not work
> >
> > if i remove
> > ip route del default via w.x.y.z dev eth1
> >
> > its work well.
> >
> > Did i leaveout anything in configuration?
>
> I'm not sure about this. At one point I understood how this worked but I
> don't anymore. There is something in the HOWTO about fallback routes. I
> think there are people here who do understand the interaction between
> different tables' default routes.

Let's see if I can explain. First: suresh, your setup ought to work.

The point of having different routing tables is exactly that: having
different routing tables. Each table is technically independent. However, if
a particular table does not come op with a route for a packet to take, the
next rule is investigated, and if it matches the packet, a route is searched
in the table looked up from that rule. For most rulesets one would end up
using the routes in table main...

In your case I don't see how that can occur, as you have a default route in
table isp1. However, what *does* occur is somewhat of a mistery to me.
Could you show us your full routing tables (ip route show table all)
as well as the routing cache (ip route show table cache) with and without
the default route via w.x.y.z dev eth1? (You may want to run a
ip route flush table cache   first... this will make the route cache
somewhat more palpable.)

Doei, Arthur.

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