[Knowledge sharing]Switch reporting many CPCAR alarms for BPDU-tunnel packets

Created Sep 29, 2018 05:29:12Latest reply Sep 29, 2018 06:32:03 250 1 1 0

Hello all,

Please check out a new post where you can find a possible cause for receiving many BDPU-tunnel packets.


Fault symptom:


Receiving a lot of CPCAR alarms reported for BPDU-tunnel packets. Even if we increased the allowed ammount of this traffic using user defined policy all the packets were still dropped.


Log message :


May 17 2018 16:59:25+02:00 DST SYS %DEFD/4/CPCAR_DROP_LPU(l)[123]:Rate of packets to cpu exceeded the CPCAR limit on the LPU in slot 0. (Protocol=bpdu-tunnel, CIR/CBS=1024/192512, ExceededPacketCount=9563)

 

Method to increase allowed ammount of this traffic  using user defined policy :

 

[SYS]display current-configuration configuration cpu-defend-policy bpdu

#

cpu-defend policy bpdu

description BPDU-Tunel

car packet-type bpdu-tunnel cir 1024 cbs 192512

auto-defend trace-type source-mac source-portvlan

 

---------

 

[SYS]display cpu-defend configuration all

Car configurations on mainboard.

----------------------------------------------------------------------

Packet Name         Status     Cir(Kbps)   Cbs(Byte)

----------------------------------------------------------------------

output ommited

----------------------------------------------------------------------

Car configurations on slot 0.

----------------------------------------------------------------------

Packet Name         Status     Cir(Kbps)   Cbs(Byte)  Queue  Port-Type

----------------------------------------------------------------------

bpdu-tunnel         Enabled         1024      192512      5         NA

 

other values ommited

 

 

This increase was not helpfull - there are dropped frames still present and grows:

 

[SYS]display cpu-defend statistics packet-type bpdu-tunnel

Statistics on slot 0:

--------------------------------------------------------------------------------

Packet Type          Pass(Packet/Byte)   Drop(Packet/Byte)  Last-dropping-time

--------------------------------------------------------------------------------

bpdu-tunnel                          0             4087481  2018-05-17 22:09:25

                                             0           357700321

--------------------------------------------------------------------------------


transparent.gifRoot Cause:

We found that the l2protocol-tunnel group-mac command has been enabled on the system view, but it

wasn’t enabled  on any interfaces.

So if the switch receive the packets with the destination MAC 0100-0ccd-cdd0 it will be sent to the CPU and then dropped:

#

l2protocol-tunnel lacp group-mac 0100-0ccd-cdd0

l2protocol-tunnel vtp group-mac 0100-0ccd-cdd0

l2protocol-tunnel cdp group-mac 0100-0ccd-cdd0

l2protocol-tunnel udld group-mac 0100-0ccd-cdd0

l2protocol-tunnel pagp group-mac 0100-0ccd-cdd0

l2protocol-tunnel pvst+ group-mac 0100-0ccd-cdd0

#

   If you don’t need configure Layer 2 protocol transparent transmission, please undo all the commands above;

   If you need this function, please also enable the l2protocol-tunnel on the interfaces.

   Then the logs about bpdu-tunnel packets lost will be disappeared.

transparent.gif
Solution:

In order to stop receiving the CPCAR alarms and pass the bpdu packets according to the user defined policy it is required to configure the l2protocol-tunnel command also on any interfaces.

  • x
  • convention:

Mysterious.color  Novice   Created Sep 29, 2018 06:32:03 Helpful(0) Helpful(0)

totally helpful
  • x
  • convention:

find what you love and let it kill you.

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