I'm facing an issue with network connectivity to a Profinet PLC device and would appreciate some help. Here's the setup:

• PC ↔ DLINK Switch ↔ Cisco C2960 ↔ SCALANCE X108 ↔ PLC Device
• Only Managed switch is the Cisco Switch, All other switches are Unmanaged
• The PLC is assigned an IP address of 192.168.101.9 and is configured with Profinet.
• Both the PC and the port connecting to the SCALANCE X108 are configured in VLAN 101. The Switch has several other VLANs for other IT infrastructure.

Issue:

• I can successfully ping and scan the Profinet PLC in TIA Portal when it's connected directly to the DLINK Switch.
• I can ping the two PLC devices (192.168.101.21, 192.168.101.22) that use Modbus over TCP/IP.
• However, when the Profinet PLC connected through the SCALANCE X108, I can no longer ping it from the PC, I think the Cisco Switch is dropping VLAN 0 frames. Priority is assigned to PROFINET real-time messages in accordance wit standard IEEE 802.1Q. The VLAN ID 0 with VLAN priority 6 is used for Profinet Real Time packets.

What I've Checked:

Since PROFINET use VLAN 0, I configured Cisco Switch port to allow this VLAN 0 traffic, I've done two approaches, the first uses a voice VLAN that will pass vlan 0. The second approach uses a trunk port.

1. Voice VLAN over access port :

Switch(config)# interface GigabitEthernet 0/16
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 101
Switch(config-if)# switchport voice vlan dot1p

2. Trunk Port:

Switch(config)# default interface 0/16
Switch(config)# interface GigabitEthernet 0/16
Switch(config-if)# switchport trunk allowed vlan 101
Switch(config-if)# switchport native vlan 101

With these approaches I'm pretty sure that Profinet devices will work on non industrial Cisco switches when these devices are directly hooked to the same switch. I need to make it work with Profinet devices spanning trough different switches.

I've also checked the Cisco switch MAC address table and ARP table on Port Gi 0/16 and the device is not showing up:

cisco# show mac address-table interface gigabitEthernet 0/16
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
 101    000e.8c87.5b71    DYNAMIC     Gi0/16
 101    000e.cf1b.1288    DYNAMIC     Gi0/16
Total Mac Addresses for this criterion: 2
cisco#

Im still not able to ping the PLC even allowing VLAN 0 through the voice VLAN and Trunking. I dont know where to check if the Cisco Cisco is actually dropping traffic

Has anyone encountered a similar issue with the SCALANCE X108 or could provide guidance on what might be wrong? Any specific configurations or checks I should perform on the SCALANCE X108 to ensure VLAN 101 traffic is passing through correctly?

Thanks in advance for your help!