Improper DCB configuration may cause RSS to become non-functional or lead to Tx hangs on Intel E8xx adapters.
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Improper DCB configuration may cause RSS to become non-functional or lead to Tx hangs on Intel E8xx adapters.

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Article ID: 449910

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Updated On:

Products

VMware vSphere ESXi

Issue/Introduction

  • Traffic is not evenly distributed within the same RSS engine, which may lead to performance degradation.  As shown in the NIC private statistics below, rxq5-8 and rxq9-12 form two distinct RSS engines, yet only a single queue is actively utilized within each engine.
rxq5: totalPkts=34409412 totalBytes=46591755707 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=3 
rxq6: totalPkts=0 totalBytes=0 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=3 
rxq7: totalPkts=0 totalBytes=0 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=3 
rxq8: totalPkts=0 totalBytes=0 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=3 
rxq9: totalPkts=21016088 totalBytes=28633917519 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=2 
rxq10: totalPkts=0 totalBytes=0 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=2 
rxq11: totalPkts=0 totalBytes=0 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=2 
rxq12: totalPkts=0 totalBytes=0 nonEopDescs=0 allocRxBufFail=0 csumErr=0 vsi=2
  • The uplink is stuck on Tx, and we observe the following logs:
2026-04-22T09:43:00.050Z -WARNING vmkwarning - [esx@4413] cpu44:1001390091) Uplink: WatchdogProcess:22615: Queue 0 of device vmnic6 stuck, resetting the device
2026-04-22T09:43:00.050Z -INFO vmkernel - [esx@4413] cpu44:1001390091)Uplink: Dev_Reset:16260: Resetting device vmnic6
2026-04-22T09:43:00.050Z -INFO vmkernel - [esx@4413] cpu33:1001390411)icen_unstable: indrv_UplinkReset:2521: 0000:e1:00.0: Reset Uplink
2026-04-22T09:43:00.050Z -INFO vmkernel - [esx@4413] cpu33:1001390411)icen_unstable: indrv_ChangeState:681: 0000:e1:00.0: Changed PF state from 4 to 1
2026-04-22T09:43:00.050Z -INFO vmkernel - [esx@4413] cpu33:1001390411)icen_unstable: indrv_PerformHardwareReset:2453: 0000:e1:00.0: Driver reset issued for vmnic6
2026-04-22T09:43:00.050Z -INFO vmkernel - [esx@4413] cpu33:1001390411)icen_unstable: indrv_UplinkQuiesceIo:2342: 0000:e1:00.0: Stopping I/O on vmnic6

Environment

Hardware: Intel Ethernet Controller E8xx series
Software: Driver versions of inbox icen-1.15.x.x and async icen-2.x.x.x and newer

Cause

The NIC requires the DCB is properly configured.

Resolution

RSS requires a valid and supported DCB configuration: either DCB must be completely disabled, or it must be enabled with a supported CEE or IEEE mode where TC0 is allocated bandwidth, as detailed below:

  1. DCB is completely disabled on the physical switch.
  2. DCB is enabled in IEEE mode (properly configured with TC0 bandwidth):
[root@localhost:~] esxcli network nic dcb status get -n vmnic10
Nic Name: vmnic10
Mode: 3 - IEEE Mode
Enabled: true
Capabilities:
Priority Group: true
Priority Flow Control: true
PG Traffic Classes: 8
PFC Traffic Classes: 8
PFC Enabled: true
PFC Configuration: 0 0 0 1 0 0 0 0
IEEE ETS Configuration:
Willing Bit In ETS Config TLV: 0
Supported Capacity: 8
Credit Based Shaper ETS Algorithm Supported: 0x0
TX Bandwidth Per TC: 80 20 0 0 0 0 0 0
RX Bandwidth Per TC: 80 20 0 0 0 0 0 0
TSA Assignment Table Per TC: 2 2 0 0 0 0 0 0
Priority Assignment Per TC: 1 1 1 0 1 1 1 1
Recommended TC Bandwidth Per TC: 80 20 0 0 0 0 0 0
Recommended TSA Assignment Per TC: 2 2 0 0 0 0 0 0
Recommended Priority Assignment Per TC: 1 1 1 0 1 1 1 1
IEEE PFC Configuration:
Number Of Traffic Classes: 8
PFC Configuration: 0 0 0 1 0 0 0 0
Macsec Bypass Capability Is Enabled: 0
Round Trip Propagation Delay Of Link: 0
Sent PFC Frames: 0 0 0 0 0 0 0 0
Received PFC Frames: 0 0 0 0 0 0 0 0

  1. DCB is enabled in CEE mode:

[root@localhost:~] esxcli network nic dcb status get -n vmnic5
Nic Name: vmnic5
Mode: 2 - CEE Mode
Enabled: true
Capabilities:
Priority Group: true
Priority Flow Control: true
PG Traffic Classes: 8
PFC Traffic Classes: 8
PFC Enabled: false
PFC Configuration: 0 0 0 0 0 0 0 0
IEEE ETS Configuration:
Willing Bit In ETS Config TLV: 0
Supported Capacity: 0
Credit Based Shaper ETS Algorithm Supported:
TX Bandwidth Per TC: 0 0 0 0 0 0 0 0
RX Bandwidth Per TC: 0 0 0 0 0 0 0 0
TSA Assignment Table Per TC: 0 0 0 0 0 0 0 0
Priority Assignment Per TC: 0 0 0 0 0 0 0 0
Recommended TC Bandwidth Per TC: 0 0 0 0 0 0 0 0
Recommended TSA Assignment Per TC: 0 0 0 0 0 0 0 0
Recommended Priority Assignment Per TC: 0 0 0 0 0 0 0 0
IEEE PFC Configuration:
Number Of Traffic Classes: 0
PFC Configuration: 0 0 0 0 0 0 0 0
Macsec Bypass Capability Is Enabled: 0
Round Trip Propagation Delay Of Link: 0
Sent PFC Frames: 0 0 0 0 0 0 0 0
Received PFC Frames: 0 0 0 0 0 0 0 0

Additional Information

Some problematic configuration examples:

  • DCB is enabled in IEEE mode, but no ETS settings are configured.

[root@localhost:~] esxcli network nic dcb status get -n vmnic9
Nic Name: vmnic9
Mode: 3 - IEEE Mode
Enabled: true
Capabilities:
Priority Group: true
Priority Flow Control: true
PG Traffic Classes: 8
PFC Traffic Classes: 8
PFC Enabled: false 
PFC Configuration: 0 0 0 0 0 0 0 0 
IEEE ETS Configuration: 
Willing Bit In ETS Config TLV: 0
Supported Capacity: 8
Credit Based Shaper ETS Algorithm Supported: 0x0
TX Bandwidth Per TC: 0 0 0 0 0 0 0 0
RX Bandwidth Per TC: 0 0 0 0 0 0 0 0
TSA Assignment Table Per TC: 0 0 0 0 0 0 0 0
Priority Assignment Per TC: 0 0 0 0 0 0 0 0
Recommended TC Bandwidth Per TC: 0 0 0 0 0 0 0 0
Recommended TSA Assignment Per TC: 0 0 0 0 0 0 0 0
Recommended Priority Assignment Per TC: 0 0 0 0 0 0 0 0
  • DCB is enabled in IEEE mode, but no bandwidth is allocated to TC0 (or TC0 bandwidth is set to 0).
[root@localhost:~] esxcli network nic dcb status get -n vmnic6
Nic Name: vmnic6
Mode: 3 - IEEE Mode
Enabled: true
Capabilities: 
Priority Group: true
Priority Flow Control: true
PG Traffic Classes: 8
PFC Traffic Classes: 8
PFC Enabled: true
PFC Configuration: 0 0 0 1 0 0 0 0
IEEE ETS Configuration: 
Willing Bit In ETS Config TLV: 0
Supported Capacity: 8
Credit Based Shaper ETS Algorithm Supported: 0x0
TX Bandwidth Per TC: 0 0 0 0 0 0 0 100
RX Bandwidth Per TC: 0 0 0 0 0 0 0 100
TSA Assignment Table Per TC: 2 2 2 2 2 2 2 2
Priority Assignment Per TC: 7 7 7 7 7 7 7 7
Recommended TC Bandwidth Per TC: 0 0 0 0 0 0 0 100
Recommended TSA Assignment Per TC: 2 2 2 2 2 2 2 2
Recommended Priority Assignment Per TC: 7 7 7 7 7 7 7 7
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