PROFINET

Information About Configuring PROFINET

PROFINET is the leading Industrial Ethernet standard that uses TCP/IP and IT standards to connect and control machines in real time. It is widely used in industrial automation and process control networks, especially for motion control and precision instrumentation. PROFINET emphasizes fast, reliable data exchange and defines communication paths to meet different speed requirements.

Conformance Classes: PROFINET has different conformance classes that define supported features.

  • Class B: Common in factory automation, it supports fast, real-time communication and diagnostics — ideal for applications like production lines and equipment monitoring. Class B includes PROFINET Real Time (RT), which prioritizes important data to reduce delays, with cycle times around 10 ms. This makes RT suitable for tasks like conveyor belt and packaging machine control. However, the switches do not support Isochronous Real Time (IRT), which is required for ultra-precise synchronization.

Communication Levels: PROFINET communication is scalable across three levels:

  • Non-Real-Time (NRT): Uses TCP/IP with bus cycle times around 100 ms.

  • Real-Time (RT): Enables faster cycle times, approximately 10 ms.

  • Isochronous Real-Time (IRT): Achieves highly precise synchronization with cycle times as low as 1 ms (not supported in Class B).

PROFINET I/O System: PROFINET I/O is a flexible communication framework for distributed automation. It uses cyclic data transfer to exchange information, alarms, and diagnostics between controllers, I/O devices, and automation systems like motion controllers.

PROFINET Device Roles

An I/O controller is a programmable logic controller (PLC) that controls I/O devices and exchanges data such as configuration, alarms, and I/O data through an automation program. The I/O controller and the I/O supervisor exchange diagnostic information. The I/O controller shares configuration and I/O information with an I/O device and receives alarms from the I/O device.

There are three main types of I/O devices:

  • I/O Devices: Field devices connected to controllers.

  • I/O Controllers: Manage and control field devices.

  • I/O Supervisors: Tools for diagnostics and configuration.

Figure 1. PROFINET Device Roles

PROFINET is designed to serve as the sole or primary management system platform for industrial networks. It streamlines device configuration and communication, reducing the need for manual setup.

Automatic Device Detection and Configuration:The I/O controller automatically detects switches using the Discovery and Configuration Protocol (DCP). It sets the device name and IP address, so you don’t need to enter Cisco IOS commands for basic configurations.

Advanced Configuration with Cisco IOS: For advanced features, like Quality of Service (QoS), DHCP, and similar capabilities, you’ll need to configure the switch using Cisco IOS commands. These advanced settings cannot be managed directly through PROFINET.

An I/O supervisor is an engineering station, such as a human machine interface (HMI) or PC, used for commissioning, monitoring, and diagnostic analysis. The I/O supervisor exchanges diagnostic, status, control, and parameter information with the I/O device.

An I/O device is a distributed I/O device such as a sensor, an actuator, or a motion controller.


Note

If Profinet DCP cannot detect the switch, PLC, or IO mac addresses, temporarily disable the firewall or virus scan from the Windows PC that installed the Siemens STEP7 or TIA Portal Automation application.

In a PROFINET I/O system, all the I/O devices communicate over an Ethernet communication network to meet the automation industry requirement for bus cycle times of less than 100 ms. The network uses switches and full-duplex data exchange to avoid data collisions. The switches play the role of I/O device in PROFINET Device Roles.

PROFINET Device Data Exchange

After PROFINET uses DCP to discover devices, including the switch, the devices establish application relationships (ARs) and communication relationships (CRs). After a connection is established and information about device parameters is exchanged, I/O data is exchanged. The switch uses non-real-time CRs to exchange the data attributes listed below.

Table 1. PROFINET I/O Switch Attributes

PROFINET I/O Switch Configuration Attributes

Value or Action

Device name

Configures a name for the device.

TCP/IP

IP address, subnet mask, default gateway, and switch virtual interface (SVI).

Primary temperature alarm

Enables or disables monitoring for the specified alarm.

Secondary temperature alarm

Enables or disables monitoring for the specified alarm.

SD card alarm

Enables or disables monitoring for the specified alarm.

RPS failed alarm

Enables or disables monitoring for the redundant power supply alarm.

Note

 

Before enabling monitoring for the RPS failed alarm, the user must configure the command "power-supply dual" in CLI to trigger an alarm when one of the power supplies is missing or inoperable.

Relay major alarm

Enables or disables monitoring for the specified alarm.

Reset to factory

Reset to factory (Mode 2: Communication parameter) Uses the PROFINET I/O controller to reset the switch communication parameter. This action removes the Profinet device ID, IP address, and configured SNMP writable MIBs.

Relay major configuration

Specifies the type of port alarm, for example, link fault, that triggers the major relay. Any port configured with the specified alarm type can trigger the major relay.

Table 2. PROFINET I/O Port Attributes

PROFINET I/O Port Configuration Attributes

Value or Action

Speed

10, 100, 1000, or auto.

Duplex

half, full, or auto.

Port mode

access or trunk.

Link status

shut down or no shut down.

Configure rate limiting

Broadcast, unicast, or multicast threshold exceeds configured levels.

Port link fault alarm

Enables or disables monitoring for specified alarm.

Port not forwarding alarm

Enables or disables monitoring for specified alarm.

Port not operating alarm

Enables or disables monitoring for specified alarm.

Port FCS threshold alarm

Enables or disables monitoring for specified alarm.

General Station Description File

PROFINET devices are integrated by using a general station description (GSD) file that contains the data for engineering and data exchange between the I/O controller, the I/O supervisor, and the I/O devices, including the switch. Each PROFINET I/O field device must have an associated GSD file that describes the properties of the device and contains all this information required for configuration:

  • Device identification information (device ID, vendor ID and name, product family, number of ports)

  • Number and types of pluggable modules

  • Error text for diagnostic information

  • Communication parameters for I/O devices, including the minimum cycle time, the reduction ratio, and the watch dog time

  • Configuration data for the I/O device modules, including speed, duplex, VLAN, port security information, alarms, and broadcast rate limiting thresholds

  • Parameters configured for I/O device modules for the attributes listed above

The PROFINET GSD file is bundled with the Cisco IOS release. After the switch boots at least one time, the GSD files for the switch are located in a directory called ProfinetGSD. In this directory, there is a zip file containing all the GSDs for all Cisco IE3500 Series Switch SKUs. The file is called CISCO_product_id.zip, for example, CISCO_IE35xx.zip.

The GSD file is in the switch and the I/O supervisor uses this file to manage the switch. For IOS XE-based platforms, the GSD file can be found in the Flash: or SDFlash: file system. If you want to load the GSD file for the Cisco IOS XE platform into the I/O supervisor, you need to copy it from the switch.


Note

You must use the GSD file that is associated with the Cisco IOS release on the switch to manage your PROFINET network. Both the I/O supervisor and the Cisco IOS software alert you to a mismatch between the GSD file and the switch's Cisco IOS software version.

The status of GSD match or mismatch can be determined using the show profinet status command.

Configuring PROFINET

You can use either the SIMATIC STEP7 or TIA Portal Automation application on the I/O supervisor, or you can use the Cisco IOS software to configure PROFINET on the switch.

After you enable PROFINET, Link Layer Discovery Protocol (LLDP) is automatically enabled on the switch because PROFINET relies on LLDP to fully function. If you disable PROFINET, you can enable or disable LLDP as needed.

Table 3. Feature history table

Feature

Release information

Feature description

VLAN 0 Priority Tagging

Release 17.18.1

This feature enables prioritization of critical traffic using 802.1Q frames with a VLAN ID of zero, ensuring higher processing priority without VLAN assignment.

Configure the default PROFINET settings on a switch

This task explains how to activate PROFINET on a switch by enabling the default VLAN 1 configuration.

PROFINET is enabled by default on all switches. The default configuration operates on VLAN 1, but you can assign it to another VLAN ID if required. By default, VLAN 1 is in a shutdown state when the switch is first powered on. To activate PROFINET on an out-of-the-box switch, you must unshut VLAN 1.

VLAN 0 Priority Tagging

Starting with Cisco IOS XE Release 17.18.1, the VLAN 0 Priority Tagging feature allows you to prioritize traffic without assigning it to a specific VLAN. This feature enables the transmission and reception of 802.1Q Ethernet frames with the VLAN ID set to zero, by retaining the 802.1P priority bits of the VLAN 0 Ethernet packets. These Ethernet frames are known as priority tagged frames. As a result, critical traffic receives higher processing priority.

Procedure

Step 1

Enter the global configuration mode, with the configure terminal command.

Example:

Switch#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.

Step 2

Access the VLAN 1 interface with the interface vlan 1 command.

Example:

Switch(config)#interface vlan 1

Specify VLAN 1 as the interface to be configured

Step 3

Enable VLAN 1 with the no shut command.

Example:

Switch(config-if)#no shut

Step 4

Exit the configuration mode.

Example:

Switch(config-if)#end

If PROFINET has been disabled, follow the specific procedure for enabling PROFINET on the switch in Enabling PROFINET.

Note

 

Cisco devices undergo the Profinet Certification process to ensure compliance with industrial automation standards. During this process, the use of non-standard protocols such as CDP results in test failures, preventing certification. As a result, Cisco devices intended for Profinet environments must use IEEE standard LLDP instead of CDP.

Enabling PROFINET

To enable PROFINET, follow these steps:

Procedure

Step 1

Enter global configuration mode:

Switch# configure terminal

Step 2

Enable PROFINET on the switch:

Switch(config)# profinet

After PROFINET is enabled, you can configure the device as described in Configuring the Switch with STEP7/TIA (recommended) or by using the Cisco IOS commands provided in the subsequent steps.

Step 3

(Optional) Set the PROFINET device identifier (ID) by using the Cisco IOS software:

Switch(config)# profinet id line

The maximum length of the ID string can be 240 characters. The only special characters allowed are period (.) and hyphen (-), and they are allowed only in specific positions within the ID string. The ID can have multiple labels within the string. Each label can be from 1 to 63 characters, and labels must be separated by a period (.). The final character in the string must not be zero (0).

For more details about configuring the PROFINET ID, see the PROFINET specification, document number TC2-06-0007a, filename PN-AL-protocol_2722_V22_Oct07, available at PROFIBUS.

This step is optional and can be done through STEP7 or TIA PORTAL STEP 7 or the TIA Portal Automation application installed on the Supervisor (recommended).

Step 4

(Optional) Change the VLAN number. The default VLAN number is 1. The VLAN ID range is from 1 to 4096. One PROFINET VLAN is supported per switch. 

Switch(config)# profinet vlan vlan_id

Note

 

You must create a VLAN before assigning a new VLAN to PROFINET if you are using a nondefault VLAN.

Step 5

Return to privileged EXEC mode:

Switch(config)# end

Step 6

Verify your entries:

Switch# show running-config

Step 7

(Optional) Save your entries in the configuration file:

Switch# copy running-config startup-config

Configuring the Switch with STEP7/TIA

Complete the following steps to configure the switch with STEP7/TIA. TIA v15.1 is used in the following example. Ensure that you do not use the CLI to configure or modify the switch configuration when PROFINET and TIA are in use.

Procedure

Step 1

Check the availability of the GSD file on the switch. You must use the same version that matches the GSD file bundled with the Cisco IOS release image.

See General Station Description File for more information.

Step 2

Install the GSD file in STEP7/ TIA:

  1. In STEP7/TIA, choose Options > Manage general stations description files, and browse to the location of the GSD file on the PC through source path.

    The tool displays all the available GSD files.

  2. Check the check box adjacent to the appropriate the desired GSD file and click Install.

Step 3

After the installation is completed, give it a few seconds to update the Hardware catalog. Add the switch from the Hardware catalog:

  1. In the Device view, configure IP address and PROFINET device name and save the configuration. These settings are for STEP7/TIA only; the switch is actually configured later during discovery steps.

  2. Configure the required expansion module or pluggable modules in Device view.

Step 4

After the device is added in the program, discover the device through the interface of the PC connected to the PROFINET topology.

Topology discovery uses LLDP for discovery. LLDP is enabled by default on the switch. You will see the new device listed as Accessible device followed by the MAC address under the network card of the PC.

In the Devices pane on the left, under Online access, find the PC network card and click Update accessible device. This initiates the discovery of all the devices in the network.

Step 5

In the Devices pane, expand the Accessible device folder, and click Online & diagnostics to further configure the device.

  1. In the IP address field, enter the IP address and click Assign IP address to push the IP address configuration to the switch.

  2. In the PROFINET device name field, enter the device name and click Assign name to push the device name configuration to the switch.

Step 6

Download the project from STEP7/TIA and go online.

  1. Compile, download, and load the project to the PLC (I/O Controller).

  2. Go online.

PROFINET Subsystem

The switch enables the PROFINET subsystem. By default, the switch automatically configures its interfaces to manage PROFINET frames with priority tagging. When the IOSd detects PROFINET traffic, it automatically applies the configuration at runtime, using the switchport voice vlan dot1p command on each active interface. This runtime configuration ensures the switch receives the priority-tagged PROFINET frames from the LAN. 

!
interface GigabitEthernet1/1
switchport voice vlan dot1p
!

Profinet Connection Configuration

When a Profinet connection/session is established, the network device automatically applies and saves the CLI configurations (including SNMP) given in the table below.

Table 4. CLI for the PROFINET Configuration

CLI

Purpose

snmp-server community private RW

snmp-server community public RO

Configure two Simple Network Management Protocol (SNMP) community strings, each with a read-write and read-only access.

LLDP

lldp timer 5

lldp holdtime 20

lldp run

Enable the Link Layer Discovery Protocol (LLDP) with a frame transmission interval of 5 seconds and a holdtime of 20 seconds.

CDP

no cdp run

Disable the Cisco Discovery Protocol (CDP).

Power-supply

power-supply dual

Set up the device to manage dual power supplies, ensuring it can operate redundantly if one power supply fails.

Preventing Default Gateway and CDP Loss During Reloads and Upgrades

Cisco IE switches have Profinet (PN) enabled by default to facilitate management through the Siemens TIA application portal, similar to other I/O devices, Programmable Logic Controllers (PLCs), and I/O devices within the Local Area Network (LAN).

Upon reloading an Industrial Ethernet (IE) switch operating on Cisco IOS XE 17.x or performing an upgrade from version 16.x, you may experience unexpected network connectivity disruptions. This phenomenon arises because the default gateway configuration fails to persist in the running configuration, resulting in its silent disappearance. Moreover, the Cisco Discovery Protocol (CDP) may also be disabled during this process. To rectify the loss of default gateway and CDP configurations, see the Recommended Solution section. While both the default gateway and CDP configurations are retained in the startup configuration, they do not appear in the running configuration post-reload or upgrade.

Technical Evaluation

When the Profinet feature is active, the Profinet subsystem conducts several critical checks to ensure proper configuration:

  • Non-Zero Values: The switch IP address configured on the Profinet VLAN, gateway address, and netmask must all be non-zero.

  • Subnet Consistency: The IP address and gateway address must reside within the same subnet.

  • Uniqueness: The IP address and gateway address must not be identical.

If any of these conditions are not met while the Profinet feature is enabled, the default gateway configuration is removed from the running configuration. Additionally, if you save this incomplete configuration to the startup configuration using the write mem command, the erroneous settings will persist through power cycles.

Recommended Solution

To rectify the loss of default gateway and CDP configurations, execute the following steps:

  1. Disable Profinet.

    Enter the no profinet command to disable the Profinet feature.

  2. Reconfigure settings.

    Manually re-enter the CDP and default gateway configurations.

  3. Save configuration.

    Use the write mem command to save the updated configuration.

  4. Verify configuration.

    Optionally, reload the switch to confirm that the configurations are correctly reflected in the running configuration post-reload.

  5. Check Profinet status.

    Use the show profinet status to ensure that Profinet is disabled.

Monitoring and Maintaining PROFINET

Table 5. Commands for Displaying the PROFINET Configuration

Command

Purpose

show profinet alarm

Displays all the alarms supported by PROFINET.

show profinet lldp

Displays whether LLDP is active or inactive on the ports.

show profinet sessions

Displays the currently connected PROFINET sessions.

show profinet status

Displays the status of the PROFINET subsystem.

Show profinet mrp ring 1

Displays the status of the MRP ring.

show lldp neighbor interface interface_number detail

Displays information about the adjacent interface.

The following example displays the PROFINET status and currently connected PROFINET sessions.

Switch#sh profinet status
Profinet                        : Enabled
Connection Status               : Connected
Vlan                            : 1
Profinet ID                     : dut
GSD version                     : Match
Reduct Ratio                    : 128
MRP                             : Enabled
MRP License Status              : Active
MRP Max Rings Allowed           : 3 

Switch#sh profinet session
Session #1
----------
Connected: Yes
Number Of IO CR's: 2
Number Of DiffModules: 0

Session #2
----------
Connected: No
Number Of IO CR's: 0
Number Of DiffModules: 2

Session #3
----------
Connected: No
Number Of IO CR's: 0
Number Of DiffModules: 0

Session #4
----------
Connected: No
Number Of IO CR's: 0
Number Of DiffModules: 0
**************************
Mode = Standard Mode

Monitoring Configuration Changes in PROFINET Sub-Systems

The PROFINET sub-system operates in real-time and adjusts the configuration of the device based on provisions made by remote engineering tools such as TIA Portal or in response to incoming network traffic. These dynamic updates to the running configuration often occur without your awareness. As a result, this can potentially lead to unexpected changes in system behavior.

To enhance user awareness and system transparency, syslog messages are generated whenever modifications occur in critical configuration fields. By monitoring these syslog messages, you can stay informed about real-time changes to the system configuration, ensuring better management and understanding of the PROFINET environment.

The following fields or protocols generate syslogs:

  • Link Layer Discovery Protocol (LLDP)

  • Cisco Discovery Protocol (CDP)

  • Simple Network Management Protocol (SNMP)

  • IP address and gateway configurations

Example of the syslog messages:

*Jun 19 14:41:11.247: %PROFINET_MODULE-6-PN_RUNNING_CONFIG: IP / netmask: persistent configuration applied
*Jun 19 14:41:11.248: %PROFINET_MODULE-6-PN_RUNNING_CONFIG: Gateway IP criteria met, configuring default gateway
*Jun 19 14:41:11.260: %SYS-5-CONFIG_I: Configured from console by vty0
*Jun 19 14:41:11.260: %PROFINET_MODULE-6-PN_RUNNING_CONFIG: CDP Global: service stopped
*Jun 19 14:41:11.276: %SYS-5-CONFIG_I: Configured from console by vty0
*Jun 19 14:41:11.280: %SYS-5-CONFIG_I: Configured from console by vty0
*Jun 19 14:41:11.280: %PROFINET_MODULE-6-PN_RUNNING_CONFIG: SNMP Global: service started
%PROFINET_MODULE-6-PN_RUNNING_CONFIG: LLDP Global: Tx Freq = 5 secs & Holdtime = 20 secs
*Jun 19 14:41:44.283: %PROFINET_MODULE-6-PN_RUNNING_CONFIG: Applying dot1p config on one or more interfaces

Troubleshooting PROFINET

The PLC has LEDs that display red for alarms. The I/O supervisor software monitors those alarms.

To troubleshoot PROFINET, use the debug profinet privileged EXEC command with the keywords listed in the following table.


Caution

Be aware that the output of a debug command might cause a Telnet connection to fail due to long debug outputs. When you use this command, use the serial or console port rather than Telnet using Ethernet to access the Cisco IOS CLI. You should use these commands only under the guidance of a Cisco Technical Support engineer.

Table 6. Commands for Troubleshooting the PROFINET Configuration

Command

Purpose

debug profinet alarm

Displays the alarm status (on or off) and content of the PROFINET alarms.

debug profinet cyclic

Displays information about the time-cycle-based PROFINET Ethernet frames.

debug profinet error

Displays the PROFINET session errors.

debug profinet packet ethernet

Displays information about the PROFINET Ethernet packets.

debug profinet packet udp

Displays information about the PROFINET Upper Layer Data Protocol (UDP) packets.

debug profinet platform

Displays information about the interaction between the Cisco IOS software and PROFINET.

debug profinet topology

Displays the PROFINET topology packets received.

debug profinet trace

Displays a group of traced debug output logs.