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Device commissioning – Rockwell Automation Ethernet Design Considerations Reference Manual User Manual

Page 58

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58

Rockwell Automation Publication ENET-RM002C-EN-P - May 2013

Chapter 3

Ethernet Infrastructure Features

Device Commissioning

There are multiple methods for assigning IP addresses. Switches on the product,
such as thumbwheels, push buttons, or HIM modules, provide a static address
that survives power cycles.

Stratix switches support DHCP port allocation. DHCP port allocation is a
hybrid solution for IP addressing because it provides easy device replacement, but
is topology dependant.

Option

Description

Static

Devices are hard-coded with an IP address.
Advantage
Simple to commission and replace
Disadvantage
In large environments, can be burdensome to maintain

Static via BOOTP
configuration

A server assigns devices an IP address.
Precursor to DHCP
Advantage
Supported by every device
Disadvantages
Requires technician to configure IP address/MAC address when a device is replaced
Requires a PC for commissioning and replacement (unless there are switches to set the

address offline)

Adds complexity and point of failure

DHCP

A server assigns IP addresses from a pool (not recommended).
Advantages
Efficient use of IP address range
Can reduce administration work load
Disadvantages
More complex to implement and adds a point of failure
Devices get different IP addresses when they reboot

DHCP option 82

A server assigns consistent IP addresses from a pool (not recommended).
Advantages
Efficient use of IP address range
Can reduce administration work load
Disadvantages
More complex to implement and adds a point of failure
Mixed environments do not always work

DHCP port-based
allocation

IP addresses are automatically assigned per physical switch port.
Advantages
Efficient use of IP address range
Eases maintenance and replacement in large environments
Disadvantage
Requires some maintenance and upkeep on a per switch basis