[Olsr-users] Question on multiple interfaces

[Thijs van Veen]

> OLSR (both v1 and v2) do not set routes to external (non-OLSR)
> networks, they just can announce the existence of these links to the
> network (and in v2, they can attach a cost to them).

> If you have a node that is connected to TWO internet providers, both
> routes will be "default routes" (0.0.0.0/0 or ::/0). 

This is pretty much what I meant by layer-2 magic. 
As far as OLSR is concerned, the forwarding sub-nodes are completely
transparent, all they do is provide access to the network(s) containing
OLSR nodes. 
In it's simplest form (only 1 wlan network to connect to), it will look
like this.
The exact number of forwarding sub-nodes will be changing from case to
case and the nodes OLSR B and C will be mobile.
I've had a similar setup with only one such forwarding node working, but
this might have been because of the default route.

                  + - - - - - - - - - +
                   |    OLSR  A   |
                   |  eth.0   eth.n |
                   + - - - - - - - - - +
                       |            \
                       |              \
                 + - - - - - +    + - - - - - +
                 |     eth    |    |     eth     |
                 |  FWD 1 |    |  FWD 2  |
                 |    wlan   |    |    wlan    |
                 + - - - - - +    + - - - - - +
                         |        /        |
                         |      /          |
                + - - - - - +      + - - - - - - +
                |    wlan   |      |    wlan    |
                | OLSR B |      | OLSR C |
                + - - - - - +      + - - - - - - +
                 
> This means the
> decision which to use is either local (and outside OLSR) or you need
> some additional information that the clients can select the outgoing
> interface.

I would think the metric cost as given by the forwarding sub-nodes would
be good enough for this as it would be rather similar to the ETX in the
LQ extension.

> If your local router has two IP addresses, you could use each of them
> as an endpoint for a tunnel for example, or you could use
> source-specific routing (we are discussing this in the IETF Homenet
> group at the moment).

The forwarding sub-nodes offer DHCP, so the nodes (should) end up with
at least a single IP address in the same subnet (172.16.0.0/16) for easy
identification.
Different IP addresses (and subnets) for the individual interfaces are
optional as required.

The network on the wlans will be the same (ad-hoc/mesh), so OLSR B can
and will get connected to both forwarding nodes at some point.
   
> In fact, the "two interface see one interface" is one of the examples
> in the NHDP document (RFC 6130).

I will make sure to give this a look.

-- 
  Thijs van Veen
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