[Olsr-dev] OLSR IPs for node with multiple interfaces

[Harald Geyer]

Hi David.

> I noticed that Markus Kittenberger (in a previous post) was talking 
> about their mesh in Vienna using 255.255.255.255 or /32 subnet masks. 
> However, I did not understand the reasoning. If you have the time, I 
> would be very interested in hearing why you do this.

There are actually two things that are peculiar about the funkfeuer
mesh in Vienna.
a) The mesh runs with public ips from two different blocks. The
ips are distributed quite randomly over the mesh (no geografic or
topology information is encoded in the ips) so in order to get
olsr broadcasts to work, we need to use the broadcast address of
255.255.255.255 - this is a olsr configuration issue, not a network
issue.

b) Since all our devices are configured according to a) and since olsrd
installs hostroutes to any device in the mesh anyway, it is possible
to use /32 subnet masks. This gives one further advantage: If there
is any traffic targetted at a device for which no routing information
is available (i.e. the device is down) then you get a clear icmp error
back instead of waiting for arp timeouts. This makes debugging the mesh
easier. - But only a minority of nodes in Vienna is configured with /32.

HTH,
Harald