'%SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0' error

Unanswered Question
Aug 31st, 2010

Hi,

we've got several error messages on our WS-C6509-E VSS switch with IOS s72033-ipservicesk9_wan-mz.122-33.SXI4.bin.

Aug 19 06:53:10.616: %SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0 (count: 1)

Aug 21 16:20:44.640: %SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0 (count: 2)

Aug 24 07:29:32.891: %SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0 (count: 3)

Aug 24 12:38:45.510: %SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0 (count: 4)

Aug 24 15:20:59.357: %SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0 (count: 5)

Aug 26 11:28:21.381: %SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0 (count: 6)

Aug 30 12:15:49.072: %SIBYTE-SW2_DFC3-3-SB_TX_FIFO_UNDRFL: TX FIFO underflow on mac 0 (count: 7)

Have tried to use standard Cisco tools to identify the error, but just got a general description that a TX FIFO underflow has occured on a MAC interface.

Does anyone know what the error exactly means and how serious it is?

Currently we do not have any production problems.

Thank you.

Below is the full list of modules and versions in VSS:

sho module switch all

Switch Number:     1   Role:   Virtual Switch Active
----------------------  -----------------------------
Mod Ports Card Type                              Model              Serial No.
--- ----- -------------------------------------- ------------------ -----------
  1   48  CEF720 48 port 1000mb SFP              WS-X6748-SFP       SAL1303GJPP
  2   16  CEF720 16 port 10GE                    WS-X6716-10GE      SAL1302FXHU
  3   16  CEF720 16 port 10GE                    WS-X6716-10GE      SAL1302FXHY
  4   16  CEF720 16 port 10GE                    WS-X6716-10GE      SAL1345327Y
  5    5  Supervisor Engine 720 10GE (Active)    VS-S720-10G        SAL1303GMGU
  8    8  Network Analysis Module                WS-SVC-NAM-2       SAD070802WN

Mod MAC addresses                       Hw    Fw           Sw           Status
--- ---------------------------------- ------ ------------ ------------ -------
  1  0024.973b.68d8 to 0024.973b.6907   1.12  12.2(14r)S5  12.2(33)SXI4 Ok
  2  0023.0455.ffb8 to 0023.0455.ffc7   1.0   12.2(18r)S1  12.2(33)SXI4 Ok
  3  0023.0455.fde8 to 0023.0455.fdf7   1.0   12.2(18r)S1  12.2(33)SXI4 Ok
  4  0026.cbb1.b7d0 to 0026.cbb1.b7df   1.1   12.2(18r)S1  12.2(33)SXI4 Ok
  5  001e.4a7e.8058 to 001e.4a7e.805f   2.1   8.5(2)       12.2(33)SXI4 Ok
  8  0003.feab.1bf0 to 0003.feab.1bf7   3.0   7.2(1)       3.6(1b)      Ok

Mod  Sub-Module                  Model              Serial       Hw     Status
---- --------------------------- ------------------ ----------- ------- -------
  1  Distributed Forwarding Card WS-F6700-DFC3C     SAL1303GH79  1.1    Ok
  2  Distributed Forwarding Card WS-F6700-DFC3C     SAL1303GH1A  1.1    Ok
  3  Distributed Forwarding Card WS-F6700-DFC3C     SAL1303GH6K  1.1    Ok
  4  Distributed Forwarding Card WS-F6700-DFC3C     SAL13463RCL  1.4    Ok
  5  Policy Feature Card 3       VS-F6K-PFC3C       SAL1302G7DF  1.0    Ok
  5  MSFC3 Daughterboard         VS-F6K-MSFC3       SAL1302G1KQ  1.0    Ok

Mod  Online Diag Status
---- -------------------
  1  Pass
  2  Pass
  3  Pass
  4  Pass
  5  Pass
  8  Pass

Switch Number:     2   Role:  Virtual Switch Standby
----------------------  -----------------------------
Mod Ports Card Type                              Model              Serial No.
--- ----- -------------------------------------- ------------------ -----------
  1   48  CEF720 48 port 1000mb SFP              WS-X6748-SFP       SAL1303GJR3
  2   16  CEF720 16 port 10GE                    WS-X6716-10GE      SAL1409C07K
  3   16  CEF720 16 port 10GE                    WS-X6716-10GE      SAL1302FZLX
  4   16  CEF720 16 port 10GE                    WS-X6716-10GE      SAL1345326K
  5    5  Supervisor Engine 720 10GE (Hot)       VS-S720-10G        SAL1303GBVK
  9   10  WiSM WLAN Service Module               WS-SVC-WISM-1-K9   SAD122601G6

Mod MAC addresses                       Hw    Fw           Sw           Status
--- ---------------------------------- ------ ------------ ------------ -------
  1  0024.973b.5828 to 0024.973b.5857   1.12  12.2(14r)S5  12.2(33)SXI4 Ok
  2  001f.6ca4.4878 to 001f.6ca4.4887   1.1   12.2(18r)S1  12.2(33)SXI4 Ok
  3  0023.0456.0d28 to 0023.0456.0d37   1.0   12.2(18r)S1  12.2(33)SXI4 Ok
  4  0026.cbb1.b700 to 0026.cbb1.b70f   1.1   12.2(18r)S1  12.2(33)SXI4 Ok
  5  001e.4a7e.7df8 to 001e.4a7e.7dff   2.1   8.5(2)       12.2(33)SXI4 Ok
  9  001d.70d1.3a30 to 001d.70d1.3a3f   2.3   12.2(14r)S5  12.2(33)SXI4 Ok

Mod  Sub-Module                  Model              Serial       Hw     Status
---- --------------------------- ------------------ ----------- ------- -------
  1  Distributed Forwarding Card WS-F6700-DFC3C     SAL1249CF4X  1.1    Ok
  2  Distributed Forwarding Card WS-F6700-DFC3C     SAL1412DD5T  1.4    Ok
  3  Distributed Forwarding Card WS-F6700-DFC3C     SAL1303GH6R  1.1    Ok
  4  Distributed Forwarding Card WS-F6700-DFC3C     SAL13463USK  1.4    Ok
  5  Policy Feature Card 3       VS-F6K-PFC3C       SAL1302G40V  1.0    Ok
  5  MSFC3 Daughterboard         VS-F6K-MSFC3       SAL1302G15A  1.0    Ok
  9  Centralized Forwarding Card WS-SVC-WISM-1-K9-D SAD122504NS  2.1    Ok

Mod  Online Diag Status
---- -------------------
  1  Pass
  2  Pass
  3  Pass
  4  Pass
  5  Pass
  9  Pass

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vladakoci Fri, 09/10/2010 - 02:46

A case has been opened at Cisco and as per them it's either an issue with a supervisor module or a card.

Supervisor modules reseating will be performed first to see if it is one of the two supervisors in VSS.

Giuseppe Larosa Fri, 09/10/2010 - 12:29

Hello Vladakoci,

the message is related to a DFC3 submodule, so I would expect that one of the following has troubles:

1  Distributed Forwarding Card WS-F6700-DFC3C     SAL1249CF4X  1.1    Ok
  2  Distributed Forwarding Card WS-F6700-DFC3C     SAL1412DD5T  1.4    Ok
  3  Distributed Forwarding Card WS-F6700-DFC3C     SAL1303GH6R  1.1    Ok
  4  Distributed Forwarding Card WS-F6700-DFC3C     SAL13463USK  1.4    Ok

However, reseating the supervisor may be of help as each DFC3C communicates with switching fabric on supervisor(s).

I would ask you to keep us informed on this issue as it may be helpful for other people.

Hope to help

Giuseppe

vladakoci Thu, 10/28/2010 - 00:36

First we performed reseating of both supervisor engines in VSS, but this did not help and still saw the error messages.

Second we replaced both supervisor engines in VSS one by one with a spare Supervisor 720 module and the error messages disappeared then.

So we identified the faulty supervisor engine on one stack member and kept the new supervisor module in it, and on the second switch kept the former supervisor engine. As we have not seen the error messages since that we think this has been solved and clearly it was one of the supervisor engines that was the cause.

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