[Olsr-users] Subnet settings of NICs and mobility

[Henning Rogge]

On 09/24/2012 11:14 AM, Vigneswaran R wrote:
> Hello Henning,
>
> I have a question based on your reply to the thread[1]. However, it is
> not related to the problem discussed there.
>
>> They have the same network address and netmask (all three have
>> 10.0.0.0/8). This cannot work, the routing code will not know where to
>> send packets.
>>
>> You have to give each interface its own unique network range.
>> (e.g. 10.1.0.0/16, 10.2.0.0/16, 10.3.0.0/16)
> [1]
> <https://lists.olsr.org/pipermail/olsr-users/2012-September/005264.html>
>
> You mean all the NICs of a single machine should be in different subnets
> for OLSR to establish routes properly, right?

They should have different subnets to make the IP stack work properly. 
Using the same subnet for all interfaces/NICs is a problem with and 
without OLSRd.

> In that case, while connecting two machines, if the NICs being part of
> the link have different subnet settings, will OLSR establish route?
> (assume that this connection happened due to node movement).

A group of NICs which might have a connection should share a subnet.

So if you use a wifi on channel X, give all NICs on this channel the 
same subnet.

It MIGHT work with the same subnet on multiple NICs because OLSRd sets 
/32 routes, but its a hack and will make looking for bugs a pain.

> +-----------------+        +-----------------+
> |eth0: 10.1.1.1/16|        |eth1: 10.2.1.2/16|
> |                 |        |                 |
> |      Node1      |        |      Node2      |
> |                 |        |                 |
> |eth1: 10.2.1.1/16|<------>|eth0: 10.1.1.2/16|
> +-----------------+        +-----------------+
 >
> When we tried the above setup a couple of months back, routes were not
> established :-(. So, we used 10.0.0.0/8 for all our NICs and found
> working. (However, as a side effect PIMd was not working -- that is
> another story).
>
> Please suggest.

Same layer-2 domain, same subnet. Different layer-2 domain, different 
subnet.

In your example eth1 on Node1 and eth0 on Node2 should have the same subnet.

I guess you do not have to wifi-cards on the same channel in one 
machine, right?

Henning Rogge

-- 
Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für
Kommunikation, Informationsverarbeitung und Ergonomie FKIE
Kommunikationssysteme (KOM)
Fraunhofer Straße 20, 53343 Wachtberg, Germany
Telefon +49 228 9435-961,   Fax +49 228 9435 685
mailto:(spam-protected) http://www.fkie.fraunhofer.de

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