User Manual

Overview
Networking Ethernet/IP networks
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It is not enough to plan and implement the proper network technology to guarantee reliability and
availability.
Switches with two voltage inputs are commonly offered to increase availability. Alarm messages can also
be sent over hardware relay contacts (for example, in the event a connection or power supply fails, etc.).
The switch can also be monitored as an alternative on a suitable management platform such as Desigo CC
via the SNMP protocol.
Moreover, provide a separate or redundant power supply on important infrastructure, key automation
stations, sensors, or actuators.
Selecting the topology is not always easy. Plant or application requirements are always the decisive factor,
however. Special attention should be directed at the network since it forms the backbone of automation
communications.
DHCP or fix IP address
The question comes up repeatedly as to whether DHCP should be used on a Desigo project.
For the sake of understanding, the following arguments pro and contra DHCP are listed here.
The Dynamic Host Configuration Protocol (DHCP) is a communications protocol where a DHCP server
automatically assigns the network configuration (e.g. IP address, subnet) to a network participant (client).
The DHCP server operates as a network service in the background and waits for client queries. The clients
can be automatically or dynamically addressed based on the information on the available address pool from
its configuration file.
There are three types of address assignment:
● Under manual assignment (static DHCP), the IP addresses are assigned to specific MAC address for an
undetermined time on the DHCP server.
● The automatic assignment defined a range of IP address on the DHCP server and automatically assigns
new DHCP clients to the MAC address. A table sets the assignment and is permanent. Assignments are
not deleted and have the benefit that a participant always receives the same IP address so that the
address cannot be assigned to another participant.
● Dynamic assignment is comparable to automatic assignment. The DHCP server does however manage
data in its configuration file on how long certain IP address may be assigned to a participant before it is
required to register on the server and request an extension. The IP address becomes available if this
does not occur and can be assigned to other participants.
The DHCP procedures do have some disadvantages on a Desigo system or BACnet network:
● Access to the automation station is only through the BACnet names.
● Devices covering BBMD functionality, such as QXM7 or assigned Desigo room automation stations
always require a fixed IP address.
● It is difficult for the user to access device when addresses change since room automation stations have
a web server on board and are operated by ABT SSA for servicing and diagnostics.
For these reasons, Desigo automation stations are assigned a fixed IP address. The advantages clear
outweigh the DHCP process, since:
● Automation stations are permanently assigned to a network and always have the same IP address.
● Simply and unique address assignments are important in the Desigo Engineering tools for service,
diagnostics, and exchange.
● It permits unique project documentation on all levels.
● The devices can be uniquely assigned for servicing and diagnostics and simplifies operation via ABT
SSA (Service and system assistant).
An IP segment can also be divided on a project-by-project bases into a part with static addresses, e.g.
automation stations, etc., and a dynamic part (DHCP), e.g. for engineering laptops.
Managed Layer 2 Switches with
Rapid Spanning Tree Protocol
Max. 20 DXR2.E.. / PXC3.E..