[OLSR-users] olsrd with 2 networks

Bernd Petrovitsch (spam-protected)
Tue Feb 7 13:39:35 CET 2006


On Tue, 2006-02-07 at 12:47 +0100, Kosta Welke wrote:
> Bernd Petrovitsch wrote:
> > On Mon, 2006-02-06 at 19:19 +0100, Andreas T√łnnesen wrote:
[...]
> >> I take it you are running on one interface? Using 255.255.255.255
> >> for broadcast should be sufficient in that case.
> > Hmm, and if I run it on several interfaces (and all of the nets are
> > equally visible on all interfaces)?
> > Of course I would use it then in all interface sections.
> 
> If the broadcast addresses for these interfaces are correct, no further 
> action on your part is required, as olsrd uses theses addresses when 
> broadcasting on an interface.

The interface will have exactly one IP address.
And actually I'm thinking on configuring /32 on the interfaces IP
address because:
- I don't have to explicitly delete the automatically added route
  afterwards.
  This may be a Linux-only problem and it doesn't hurt really, but it is
  far from elegant (and error prone during debugging).
  Think of hosts with several OLSR interfaces (e.g. on antennas,
  LANs, OpenVPN endpoints).
- IMHO this is the conceptually *only* correct interface address
  configuration since OLSRD routes (conceptually) only hosts and not
  subnets (with != /32 netmask).
  So relying on some "artificial" subnet declaration looks somewhat
  "fishy" to me.
  "artificial" because it has nothing to do with routing (except that it
  defines a broadcast address. But I can configure it also in the config
  file) or broadcast or collision domains but more a pure administrative
  given value.
  I fear I have to read the RFCs and similar docs soon....

> The broadcast option is only needed when you want to connect to nodes 
> that are in your one-hop radius, but have a different network address.

Yes, but the next hop has potentially an address from a complete
different subnet.

> A (bad) example would be an ethernet where 10.0/16 and 192.168/16 

See it as an example setup for this discussion - there are several
reasons why such setups may make sense and they are IMHO absolutely
unavoidable in the mid-term.

> addresses are mixed. There, if all nodes use 255.255.255.255 as 
> broadcast address, everyone would see each other.

	Bernd
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