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Entry type: FAQ Entry ID: 24947500, Entry date: 01/16/2015
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Which settings do you have to comply with in a PROFINET RT network in conjunction with VLAN switches?

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  • Associated product(s)
Priority is assigned to PROFINET real-time messages in accordance with standard IEEE 802.1Q.

The VLAN ID 0 with VLAN priority 6 is used for this. The general procedure for assigning priority is described in the standard IEEE 802.1P.


Fig. 01

In order for the PROFINET real-time communication to be possible also in a Virtual Local Area Network (VLAN) and thus also over switches that can evaluate the VLAN tag, the switches must support the following:

  1. PROFINET real-time messages with Ethernet type 0x8892 must be accepted and forwarded. 
  2. PROFINET real-time messages with VLAN ID 0 must be accepted by the switch and tagged with the prioritization by the configuration in the switch in a separate VLAN x.


Fig. 02

The VLAN ID 0 of the PROFINET real-time message must be set by Switch 1 to any VLAN ID (tagged VLAN), for example VLAN ID 2. This permits the priority still to be taken into account. In this way the switches can continue to recognize the PROFINET real-time messages as prioritized. The last switch that forwards the PROFINET real-time message to a terminal node or other IO device can remove the VLAN tag from the PROFINET real-time message before forwarding on the target port (untagged VLAN). All these settings have to be configured in each switch.

Notes

  • In this example the VLAN ID 2 is used for PROFINET real-time communication. You can use any VLAN ID for your own VLAN for PROFINET real-time communication.
    The priority is set with the VLAN so that the PROFINET real-time message is handled with priority.
  • The switch must not discard any multicasts (PROFINET IO has reserved multicast addresses which are used to find devices, etc.). Some manufacturers have Multicast disabled as default setting.
  • Change the security settings (like ACL, firewall, etc.) of the switch so that the switch ports can receive data packages from an sender (also data packages from a port with multiple MAC addresses, because LLDP, for example, uses an separate MAC address per port).

The following SCALANCE products can evaluate the VLAN tag so that it can be used in a VLAN with PROFINET real-time communication:

  • Industrial Ethernet Switches SCALANCE XM-400 and SCALANCE XR-500
    More information about configuring the VLANs in SCALANCE X-400 and SCALANCE X-500 is available in the manual in Entry ID 19625108.
  • Industrial Ethernet Switches SCALANCE X-300 and SCALANCE X-400
    More information about configuring the VLANs in SCALANCE X-300 and SCALANCE X-400 is available in the manual in Entry ID 109478046
  • Industrial Ethernet Switches SCALANCE XB-200, SCALANCE XC-200 and SCALANCE XP-200
    More information about configuring the VLANs in SCALANCE XB-200, SCALANCE XC-200 and SCALANCE XP-200 is available in the manual in Entry ID 109750283 
  • SCALANCE W Access Points and Client Modules
    More information about configuring the VLAN in SCALANCE W is available in the following manuals:
    - SCALANCE W780 / SCALANCE W740 in compliance with IEEE 802.11n: 109751568
    - SCALANCE W760 / SCALANCE W720 in compliance with IEEE 802.11n: 109751601
    - SCALANCE W770 / SCALANCE W730 in compliance with IEEE 802.11n.: 109751537
    - SCALANCE W-700 configuration manual: 79695884
   
Additional Keywords
Virtual Local Area Network, SCALANCE
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