Siemens SIMATIC NET System Manual page 138

SCALANCE network components
4.5 SCALANCE X Industrial Ethernet Switches
IGMP snooping and IGMP querier
IGMP (Internet Group Message Protocol, RFC 2236) is a protocol used for the group
management of IP multicasts.
The group management is on a central device, for example a switch. With IGM snooping, the
switch (IGM querier) queries the multicast group membership of its connected devices. The
switch notes the outgoing interfaces on which devices are located that want to receive
certain multicast IP packets. The switch enters the devices in a list (MAC filter table). When a
switch receives a multicast, the message is forwarded only to the members of the multicast
group. The multicast data traffic is filtered as a result and the load on the network is limited.
Bundling network links for redundancy and higher bandwidth
Link aggregation according to IEEE 802.3ad allows several links between neighboring
devices to be bundled to achieve higher bandwidths, see section "Link aggregation
(Page 97)".
Topology support (LLDP)
The topology is identified using LLDP (Link Layer Discovery Protocol). The devices
exchange LLDP frames with each other. The information is stored and can be represented
graphically by network management software. In the default setting, LLDP is enabled for all
ports; in other words, LLDP frames are sent and received on all ports.
Using the GARP VLAN Registration Protocol (GVRP)
Whether or not a port belongs to a VLAN is set dynamically using GVRP frames.
Forwarding of multicast frames with GMRP (Generic Multicast Protocol)
GMRP is a mechanism for efficient forwarding of multicast frames. With a GARP Information
Declaration (GID), a node registers with the IE switch as recipient for a multicast address.
The IE switch sends this registration to its ports. As a result, this address is also known to
other IE switches and they send multicast messages for this address only to ports that have
received a registration for this address.
Fast redundancy in the ring
The SCALANCE X-200, X-300, X-400- and X-500 switches have functions that allow the
setup and management of redundant networks in a ring topology. These networks can
handle the failure of individual nodes or cable sections and "divert" the data traffic so that the
network remains available.
The following redundancy methods are possible:
● MRP in the ring with a maximum reconfiguration time of 200 ms, see section "MRP
(Page 84)"
● HSR with a maximum reconfiguration time of 300 ms, see section "HRP (Page 89)"
● MRPD (IE switches with IRT) with 250 µs reconfiguration time, see section "MRPD
(Page 88)"
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System Manual, 09/2019, C79000-G8976-C242-10
Industrial Ethernet