Hi,

I am facing an issue where the OAI gNB running in DU mode is not receiving any fronthaul traffic from the RU. The DU logs show RX = 0 and all uplink counters (PUSCH/PRACH) remain zero, even though the RU and DU are connected and PTP synchronization is working.

My setup is as follows:

OAI gNB configured as DU (7.2 split)

RU: ProtoRU connected to USRP X310

The USRP X310 is connected to the RU host machine over a 10G Ethernet interface(enp1s0f1 on proto-ru host machine).

Fronthaul connection between OAI DU and ProtoRU is also 10G Ethernet(enp1s0f0 on both machines).

Interface used on both DU and RU for fronthaul: enp1s0f0

NIC: Intel X540-AT2 (10G)

Direct Ethernet connection between DU and RU

PTP time synchronization is enabled on both DU and RU on the same interface (enp1s0f0). I can observe PTP packets (Sync, Follow_Up, Delay_Resp) on the DU using tcpdump, so timing appears to be correct.

On the DU side, I have created a single VF on enp1s0f0 and bound it to vfio-pci for DPDK usage. The same VF is being used for both C-plane and U-plane traffic.

However, the DU logs consistently show:

RX = 0

PUSCH = 0

PRACH = 0

Total received messages = 0

TX is active

Additionally, when I capture traffic on the DU interface using tcpdump, I only see PTP multicast packets and no fronthaul (eCPRI/FHI) traffic.

Based on the ProtoRU documentation, this behavior may be due to MAC address mismatch or VLAN mismatch. I need clarification on the correct configuration:

For MAC address configuration:

What should be used as du_mac on the RU side? Should it be the MAC address of the DU VF (DPDK interface) or the physical NIC (enp1s0f0)?

What should be used as ru_addr on the DU side? Should it be the MAC address of the RU fronthaul interface (enp1s0f0), the USRP interface(enp1s0f1 on RU host), or another interface on the RU host?

Specifically, does ru_mac_addr refer to the MAC of the physical NIC connecting DU and RU (enp1s0f0), or the MAC of the interface used between RU and USRP (for example enp1s0f1) or MAC of USRP?

Regarding VLAN configuration:

How is VLAN expected to be configured on ProtoRU?

I configured the VF on the DU side with VLAN ID 5 during VF creation, but in the gNB logs it still shows VLAN = 0 for both C-plane and U-plane.

How can I verify whether ProtoRU expects tagged or untagged traffic?

How is VLAN (for example VLAN ID 5) configured for the USRP b210/ProtoRU setup?

VF usage:

Is it valid to use a single VF for both C-plane and U-plane, or is it required to use separate VFs?

Additional information:

IOMMU is enabled and vfio-pci is working correctly

Setup has been reconfigured from scratch after reboot

Issue persists consistently

Any Clarification on correct MAC address mapping, VLAN configuration, and expected fronthaul behavior would be very helpful.

Thanks and regards,
Vishwa