The Facts about Industrial Ethernet Switches

There are many misconceptions about Industrial Ethernet switches. Some vendors are providing misleading information indicating that their switches have some special features required for Ethernet/IP or Profinet. Ethernet Direct will support the device recognition and device profiles of the various Industrial Ethernet protocols including LLDP and IEEE 1588. Remember, these are 'open' protocols and not proprietary 'clubs' that limit membership. What limits the ability to support these standards is the memory, CPU power and the firmware set of the switch.

Ethernet Direct switches have the necessary processor power and memory to support these evolving standards. Since Ethernet and Ethernet switches are a true standard, they are, one to one, replaceable with any vendor. Variations are easily seen in the published specifications. Managed Switches in the commercial world support SNMP v1, v2, or v3 in addition to RFC 1493 and can be monitored by open network management packages and not the vendor specific software. IntraVUE is the open standard for Industrial Ethernet network management applications and works with vendors who support true management of their switches.

We have made it easy to compare many switches to Ethernet Direct - such as,  Hirschmann ,  N-Tron ,   Phoenix ,   Siemens ,   Sixnet ,  Moxa  and  Contemporary Contols.

The benefits of Industrial Ethernet switches vs. commercial grade switches:

  • Greater Temperature range - wider and higher, typically -10 C to +70 C
  • Ability to handle large fluctuations in power
  • Redundant power sources
  • DIN rail mounting with industrial equipment
  • Longer MTBF times - typically 215,000 hours +
  • Better shock,vibration, RFI and EMI resistance
  • No moving parts - no fans

The Requirements for Industrial applications:

  • IGMP Snooping for multicast traffic control ( Ethernet/IP implicit messaging )
  • Port Mirroring - to help in Diagnostics
  • RMON ( remote monitoring ) - to help in Diagnostics
  • Redundant power sources
  • DIN rail mounting with industrial equipment
  • Metal cases for heat dissipation
  • Redundancy schemes - Ring preferred
  • Install it, program it, BE ABLE to monitor the switch and use diagnostics to troubleshoot the network devices

The Facts about SNMP Management

'Smart' or 'Lean Managed' switches are not SNMP managed switches - they are missing important features. These switches may have IGMP enabled from the factory - this is not always a desirable situation. Ethernet/IP requires IGMP snooping to control the PLC's multicasting, but to have every switch set as a 'Querier' is not always desirable in an application.

SNMP Features

Managed switches should be a major consideration if the health of the network is important. A managed switch supports SNMP v1, v2, or v3 and it allows communication with network management packages. This requires greater intelligence at the switch, and there is a wide variation in the performance of SNMP in Industrial switches. several companies are misleading customers by calling switches that have a web-server or answer to specific SNMP queries as 'smart' or 'managed'. Several vendors state that SNMP is a security risk, implying that, although this is a standard method for all applications, it is a problem for automation applications. A quick look will show that these vendors do not have SNMP capability in their switches to try to reduce costs.

Ethernet Direct switches operate as fully managed SNMP switches with the same or better performance as Cisco and Hirschmann at much less cost.

IGMP Snooping

With Unicast traffic, the switch learns the MAC address by looking into the source address field of every frame. With Multicast packets, the switch must deal with a multicast MAC header, which may or not appear in its Bridging Table. As a result, multicast packets are copied and transmitted ( 'flooded' ) to every port of the switch. During 'Multicast Floods', devices are unable to use the network, preventing control data from being sent. The effect of 'Multicast Floods' is particularly serious with full duplex links, because the bandwidth used is proportional to the number of attached nodes - each of which invites a multicast packet.

IGMP Snooping prevents a flood of packets from 'flooding' a network segment where a node is not interested in receiving the packets. IGMP is an integral part of IP and is used by Layer 3 switches ( routers ) to report their multicast status to nearby routers. Because a router must look into the MAC header and 'snoop' into the IP header before handling the packet, this capability is called 'IGMP SNOOPING'. The multicast packet is then directed only to those nodes listed in the router's table of learned multicast addresses said to be interested in receiving the traffic.

  • ABSOLUTELY REQUIRED for I/O over Ethernet/IP, unless using ProfiNet I/O, which does not use multicasting
  • Controls Multicasting by PLCs
  • Enable the IGMP Querier in networks' Managed switches
  • A multicasting PLC can reduce the performance of switches to that of Hubs !
  • Network bandwidth is severely compromised by a PLC that is multicasting

GMRP ( GARP Multicast Registration Protocol )

GMRP is employed to configure switch ports dynamically to forward IP multicast traffic reports used by Multicast Hosts.

VLAN ( Virtual Local Area Network )

A Virtual LAN is a way that allows switches to create a single Collision Domain logically even though the nodes are on separate network segments physically. The benefit is that instead of physically installing hardware to segment a network, VLANs can do it through software. VLAN configuration can be based on port ID, MAC or IP addresses. The Port based VLAN standard is IEEE 802.1q. Each switch in the VLAN must be able to implement the port based VLAN policy. Ethernet Direct switches support IEEE 802.1q port based VLANS.

RMON ( Remote Monitoring Protocol )

RMON is an alternative to SNMP that transfers the monitoring responsibility to the managed switch, rather than to the Network Monitoring Software staion. The switch can transmit data at convenient times and send alarms to the station without waiting to be polled.

MIB ( Management Information Base )

MIBs are a database maintained by the SNMP package that logs the device's condition and the traffic through the device. The IETF has defined MIBs for ethernet switches.

MIBs are critical to interoperability. The NMS talks to the device through SNMP, but pulls information from the switch's MIBs. A common SNMP and MIB structure make it possible to operate different vendors' switches on the same network because the NMS can work with a common interface.

Managed Ethernet Direct switches incorporate SNMP V1/V2c agents and MIB-II objects. Managed Ethernet Direct switches interoperate with all NMS based software that can read MIB data directly - such as Network Vision's IntraVUE.

Ring Redundancy

The use of a ring for redundancy or failure recovery is common among suppliers. Since there is no IEEE or IETF standard, each supplier has a slightly different scheme and thus, proprietary method. For this reason, many customers are not selecting ring redundancy - it would lock them into a particular supplier. Those customers choose Rapid Spanning Tree - it is another redundancy scheme and is an IEEE standard that can be used for most applications. Ring Redundancy must be configured in managed switches using, according to the vendor, pre-defined ports, and one switch must be defined as the 'ring manager'. Ethernet Direct switches allow any ports to be used as 'ring' ports.

Rapid Spanning Tree Redundancy ( RSTP )

This redundancy scheme allows a back-up path to be put in a standby mode and activated upon failure of the primary path. The network topology CAN be in a ring - similar to Ring Redundancy. Different switch vendors that support RSTP in their managed switches can be used in the same network segments - RSTP is an IEEE standard. Users must configure RSTP in managed switches - defining various aspects of the configuration.

How difficult is it to learn how to set up managed switches ?

It depends on how the switch needs to be configured - most parameters are very easy, such as:

  • Setting the IP address and giving the switch a name, location and description ( all optional )
  • Enabling the IGMP Snooping
  • Port Control - turning off unused ports
  • Security - entering the IP addresses ( laptops, desktops ) allowed for management changes
  • Ring Redundancy - entering the ports used for the ring

Parameters that are more difficult: you should read the manual:

  • VLANs
  • RSTP Redundancy - setting all the necessary parameters

Many Parameters do not have to be set - they can be left in the default setting.

We can help you with switch management - our EDucational Link Support Library contains many presentations and videos that explain and demonstrate how to set up the parameters for your application. You can always call us for help.

To sum it all up ...

Always purchase switches that are true SNMP managed. They will operate with any others that are SNMP managed. A switch labeled as a 'Smart switch' is probably not a true SNMP managed switch and may have inferior chipsets - it may have some SNMP features, but will not work properly with other switches and the NMS software on the network.

Ethernet Direct makes fully managed, true SNMP switches affordable for all applications.