Using multiple interfaces

Nodes participating in an OLSR routing domain can be multi-homed. That means that they can run OLSR on multiple communication interfaces using multiple identifiers. Multiple interface declaration(MID) messages are used to diffuse information about multi-homed nodes. A MID message is essentially just a list of addresses used by interfaces on which a node runs OLSR. The format of the MID message is displayed in figure 3.8. The data is sent as the message part of an OLSR-message included in an OLSR packet as seen in fig 3.1.

Figure: The OLSR MID message.

Upon receiving a MID message, a node updates is Multiple Interface Association Information Base according to the information carried in the message. All OLSR interfaces listed in the MID message are registered on the main address of the originator. The main address is found in the originator field of the OLSR-message header. When adding a route to a node, OLSR will add routes to all addresses of other interfaces on which the remote node runs OLSR, using the same path.

All nodes running OLSR on more than one interface are generating MID messages on regular intervals. MID messages are to be flooded throughout the network using the default forwarding algorithm.