Installation guide

Network Infrastructure for EtherNet/IP™
6-75
Infrastructure Application Scenarios
Figure 6-9 depicts the logical view of the system set up as two VLANs. Here, ports 1, 3, 4, 5, and 6
belong to VLAN 1; ports 2, 7, 8 and 9 belong to VLAN 2. For more distributed applications, VLANs can
also be implemented across multiple switches.
Figure 6-9 Logical View of Two Single-Controller Systems Sharing a VLAN-enabled Managed Switch.
6.3.2 Multiple Single-Controller Systems with Data Sharing
Consider the example shown in Figure 6-9 but with the need for data sharing. If programmable controllers
need to share data or if input data produced by one more of the I/O devices needs to be shared, VLANs
are not an option. Infrastructure requirements for a network serving these applications are the same as for
an isolated network with a single controller as described in 6.2.2 Systems with High I/O Count. Even with
one switch, the number of devices connected to the network and the number of CIP connections demand
IGMP snooping and query to prevent a multicast overloading of devices.
6.3.3 Isolated Systems Summary
In small isolated EtherNet/IP networks with a single controller, control of IP multicast traffic using IGMP
snooping may not be required. In these cases, unmanaged switches may be used, given that the overall
multicast traffic load is calculated or the system pre-tested to prevent device shutdown from multicast
traffic overloads. In cases when unwanted multicast traffic affects performance of HMI workstations, a
separate network for controller-HMI communication should be used.
In large isolated networks when unwanted multicast traffic also affects the performance of traffic
producers (remote I/O, drives, etc.), managed switches with IGMP snooping could be used in
combination with unmanaged switches to lower total system cost. For maximum system performance, all
managed switches with IGMP snooping should be used. When IGMP snooping is used, one of the
switches must support the IGMP query function.
In isolated networks with multiple controllers that do not share data between them, managed switches
with VLAN functionality may be used to increase control performance by isolating traffic. If data sharing
between controllers (i.e., implicit messaging) or the use of produce-consume tags is required,
infrastructure requirements are the same as those for an isolated network with a single controller. The
same is true when controllers share remote inputs.
I/O
11
I/O
12
I/O
13
Programmable
Controller 1
Workstation 1
I/O
21
I/O
22
Programmable
Controller 2
1
2
3
4
5
6
78
VLAN 1 VLAN 2
Switch
Workstation 2
9