Network structures and network configuration
2.3 Media redundancy
Industrial Ethernet
82 System Manual, 09/2019, C79000-G8976-C242-10
For a redundant link as shown in the figure, two devices must be configured as standby
redundancy switches within a network segment. Here, network segments are rings with a
redundancy manager (RM, in the example, the SCALANCE X202-2IRT switches). Instead of
rings, network segments might also be linear.
The two X202 devices connected in the configuration exchange data frames with each other
to synchronize their operating statuses (one device becomes the master; the other device
becomes the slave). If there are no problems, the link to the other network segment is only
active at the master. If this link fails (for example due to a link-down or a device failure), the
slave activates its link as long as the problem persists.
2.2.6 VLAN
Virtual Local Area Network
VLANs are virtual network segments in a physical network that are assigned to the nodes
during configuration. In contrast to the physical network, a VLAN is not spatially restricted.
This allows nodes to be put together in logical groups according to their function (VLAN
groups). VLANs can be set up without modifying the physical network.
SCALANCE X and SCALANCE W support port-based VLAN. For the parameter assignment
of the VLANs, a VLAN ID is assigned to the individual ports of a SCALANCE device.
Multicast and broadcast messages are possible only within the boundaries created by the
logical network structure, in other words, between ports with the same VLAN ID.
This segmentation not only reduces network load because broadcasts can be limited to a
practical number of end systems. VLANs also increase the security of a network since no
node can listen to the data traffic of other nodes any more on unless they are a member of
this VLAN.
To identify which packet belongs to which VLAN, the Ethernet frame is expanded by 4 bytes
(VLAN tagging). This expansion includes not only the VLAN ID but also priority information.
2.3 Media redundancy
2.3.1 Options of media redundancy
There are various options available to increase the network availability of an Industrial
Ethernet network with optical or electrical linear bus topologies:
● Mesh networks
● Parallel connection of transmission paths
● Closing a linear bus topology to form a ring topology
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