User's Manual

NETNode
Phase 1 and 2 Units
NETNode
User Manual
NETNode-V2.3
8-81
DS000034 Unclassified
8. Interlink Mode
Normally IP networks do not allow multiple routes from an IP source to an IP destination
address. This precludes multiple nodes to be connected to the same IP backbone network.
For example in a city it is often advantageous to have multiple high points on the same Mesh
all connected to the same IP backbone. In this example connection of two NetNodes onto
the same IP backbone would cause a loop to be created in the network.
In practice each NetNode identifies this network loop occurrence (same MAC address
appearing on multiple ports) and blacklists the entry for 30 seconds, to prevent this
happening.
However, it can be extremely useful to be able to connect multiple NetNodes to the same
backbone. For example, a city Mesh system may have two nodes on two different buildings.
In this example it may be that a mobile node is only served by the one of the two nodes (for
example Mesh #1 in the diagram below), and if this not the node connected to the backbone
then IP forwarding over the radio link would have to take place. This reduces the overall
network capacity; as the hop means information has to be sent twice over the radio network.
8.1. Operation
Interlink mode replaces the radio links between the Mesh nodes on the backbone with an IP
tunnelling protocol over the IP backbone. To make this IP tunnelling possible one of the
NetNodes acts as a master allowing both tunnelling data and the main IP data through the
Ethernet interfaces while the other nodes act only as slaves just allowing IP tunnelling data
to and from that node.
Mesh #1
Mesh #2
Camera
IP Backbone