Rules for Connectivity
Original instructions
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Introduction
The local rack within an M580 system can have different combinations of Ethernet communication modules. This topic describes the networks that are created when the BMENOC0321 control network module is configured in different ways.
Network Types
A local rack contains one CPU and up to six communication modules, only one of which can have the IP forwarding service enabled. The BMENOC0321 module can communicate with other modules and devices in the system for various network combinations depending on the status of the backplane connection (enabled or disabled):
In this illustration, the backplane connection on the local rack is disabled (red arrow). Therefore, the IP forwarding service is disabled. In this example of isolation, there is no transparency between the device network and the control network: 
1
The local rack has no Ethernet backplane connection between the M580 CPU (and other devices in the device network) and the BMENOC0321 module with the IP forwarding service disabled. 
2
The device network is connected to the CPU on the local rack. 
3
The BMENOC0321 module is connected to a control network with redundant links.
In the next illustration, you can enable the IP forwarding service among three configured networks because the backplane connection on the local rack is enabled (green arrow):
Network
Ports
device network
Ethernet backplane port
extended device network
service port (ETH 1)
control network
ETH 2, ETH 3
In this example, the IP forwarding service is enabled to allow network transparency. The BMENOC0321 module uses the backplane connection (green arrow) to communicate with the device network: 
1
The local rack includes a backplane connection (green arrow) between the M580 CPU and the BMENOC0321 module with the IP forwarding service enabled. 
2
The device network is connected to the CPU on the local rack. 
3
The BMENOC0321 module is connected to a control network. 
4
The service port on the BMENOC0321 module is connected to an extended device network.
Using Different Services and Protocols
The status (enabled or disabled) of one service or protocol can affect the use of other services and protocols. This table shows the possible combinations of services when they are enabled or disabled for the BMENOC0321 module:
IPsec protocol
IP Forwarding Service
Ethernet Backplane Port
on
off
off
off
on
on
off
off
on/off