Rockwell Automation Ethernet Design Considerations Reference Manual - Manual (Page 29)

Rockwell Automation Publication ENET-RM002C-EN-P - May 2013 29
Ethernet Infrastructure Components Chapter 2
Unmanaged versus Managed Switches
Unmanaged switches are relatively inexpensive and simple to set up, but they do
not provide any management capabilities, security, or diagnostic information.
Therefore, they are difficult to troubleshoot.
As a general rule for unmanaged switches, make sure of the following:
• Your application does not contain I/O traffic
or
• Your application has I/O control and the following is true:
–
The network is not directly connected to the IT network
– All nodes on the network are Rockwell Automation devices
– There is no potential to overload a device with traffic
Managed switches are typically more expensive than unmanaged switches and
require some level of support for initial configuration and replacement. However,
managed switches provide advanced features, which can enable better network
performance in your control system. Managed switches are able to manage
multicast traffic and provide diagnostics data, security options, and other
advanced features.
Autonegotiation
Autonegotiation lets devices select the optimal way to communicate without
requiring you to configure the devices. However, if you connect a
manually-configured device to an autonegotiation device, a high rate of data
transmission errors can occur.
All 100 Mbps devices are required to support autonegotiation, but most existing
10 Mbps devices do not. Select a switch that supports both speeds to enable you
to connect to existing devices that use the slower rate.
Switch Type Advantages Disadvantages
Managed • Ability to manage multicast traffic
• Diagnostics data
• Security options
• Additional advanced features
• Network segmentation features
• Network resiliency features • More expensive
• Requires some level of support and
configuration to start up and replace
Unmanaged • Inexpensive
• Simple to set up
• 'No Config' replacement • No network segmentation
• No dagnostic information
• No port security
• No traffic management
• No network resiliency