[Babel-users] Specifying the routing table of exported routes

[Henning Rogge]

On Thu, Aug 27, 2015 at 12:49 AM, Juliusz Chroboczek
<jch at pps.univ-paris-diderot.fr> wrote:
>> Then we can have the following order of routing tables on routers:
>>
>> babel
>> olsr
>> babel_default
>> olsr_default
>
> Mitar,
>
> I'll be glad to implement the hack that you require, but let's please
> think whether we can manage to avoid it.  What's wrong with putting both
> OLSR and Babel routes into a single table, and using a higher kernel
> priority for OLSR routes?  If you do that, the most-specific rule will
> cause host routes to be preferred to default routes, and the kernel
> priority will be used to prefer routes from one routing protocol to the
> ones from the other when they have equal specificity.
>
> Babeld's kernel priority can be tuned using the "kernel-priority" config
> file directive.  I have no idea whether something similar can be done with
> olsrd.  Henning?

Juliusz,

this feature has been around for olsrd for a long while... and I added
it to olsrd2 with an optional plugin called "route_modifier".

The "default route into its own table" is used for more complex setups
where you have different kinds of internet uplinks (e.g. the normal
one for your traffic, a VPN for mesh traffic) or where you don't want
to share your internet uplink but use it locally. All of this has been
integrated to some amount in a lot of Community Mesh firmwares in form
of complex policy rules... rules that can be made more sane if you put
certain routes from the routing protocol (e.g. the default route) into
a table of its own.

I am not completely sure if it could not be done without the feature,
most likely there is a complexity tradeof with the policy rules going
on.

Putting babel and olsrd into different tables allow you to run them
side by side without source-specific routing. Olsrd1 does not support
source-specific routing, so it cannot share a routing table with Babel
(unless you want the default routes of one routing protocol interfere
with the normal ones of the other).

Henning