User Guide

NETNode Operations Guide
Commercial in
Confidence
IP Mesh Systems
000-130
R1.8 2015-07-24
Commercial in
Confidence
Page 2-28
1. IP packets with destination address 224.0.0.0 are blocked; these are used internally
within the MESH.
2. IP packets with destination addresses 224.0.0.1 to 224.0.0.255 and 239.255.255.250
(SSDP) are flooded to all nodes and interfaces regardless of being members of the group
or not.
3. All other multicast packets are forwarded only to nodes and interfaces which are
members of the group.
Although non-registered groups should be forwarded to all destinations, this is prevented in
the MESH to control bandwidth.
There are two types of interface as far as IGMP is concerned:
1. Multicast-router interfaces – these interfaces lead towards multicast routers or IGMP
queriers
2. Group-member interfaces – these interfaces lead towards hosts
IGMP Querier 2.6.2
A querier is required on the network to ensure proper functionality of the IGMP protocol. A
querier periodically sends out a IGMP general query which causes each host to send out a
membership report for each of its’ group. This in turn refreshes the multicast routing tables
in the routers. Without this, the table entries would eventually timeout and become void.
There is usually only one querier on the network. This is the multicast router with lowest IP
address, and any routers with higher addresses fall silent.
NETNodes act as multicast routers. By default, a NETNode will become a querier at start up,
and will continue to send queries if it has the lowest IP address of all the NETNodes and
multicast routers.
Connecting a NETNode to a Multicast Router 2.6.3
To let IGMP function correctly between MESH and an external multicast router, the ports
connected between the multicast-router and the NETNode must be set to forward IGMP
membership reports. For the NETNode the Eth1 or Eth2 check boxes must be ticked
(depending on which port the router is connected to), and a similar procedure repeated on
the multicast-router. This will forward IGMP reports for both LAN and all VLANs.
Alternatively, if the external multicast-router management interface is not accessible, and the
multicast router has a lower IP address than all MESH nodes, then it is necessary to start up
a second querier on a NETNode using the IGMP Force Query popup panel. This will cause
the external multicast router to continue to forward IGMP membership reports to the MESH.
A querier can be setup for each VLAN. The presence of a forced querier will automatically
prevent any other (non-forced) queriers starting up on the local (but not on a remote) MESH
network.
Note: To prevent excess network traffic only one forced querier per VLAN should be set
on the MESH network.
1. Connect your PC to the NETNode and log on.
2. Navigate to the Global Settings tab.