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High COPP drops on class ip-exeptions

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  • 1.  High COPP drops on class ip-exeptions

    Posted Mar 05, 2026 10:05 AM
    Dear Community,
     
    on our core-switch (which is doing all of the routing) we see a lot of copp drops on class ip-excption - constanty about +70%.
    copp policy is default!
    current statistics shown on cli:
    Statistics for CoPP policy 'default':
    Class: ip-exceptions
    Description: Routable packets that would exceed the MTU for the
                 egress interface, packets that trigger ICMP redirects,
                 and packets with TTL/hop_limit=1 that are discarded
                 when routing through the switch.
        priority             : 0
        rate (pps)           : 100
        burst size (pkts)    : 100
     
        packets passed   : 672142289          packets dropped  : 1915193307
     
    A bit of detail about our Layout:
    We do have a Core (which is doing routing) consisting of 2 8360 in an VSX-Pair. Here we see the copp drops!
    We do have Top-of-Rack Switches (also 8360 as VSX Pairs) where our servers are connected.
    Then we have Edge-Switches (6300M in VSF Stacks) where Client Devices are connected. 
    Here a scheme:
    image
     
    Software Version on all Switches is 10.13.1110
     
    According to documentation the class ip-exceptions hits on:
    Routable packets that would exceed the MTU for the egress interface, packets that trigger ICMP redirects,
    packets with TTL/hop_limit=1 that are discarded when routing through the switch.
     
    What I checked so far:
    • I checked MTU Size: we use MTU size 9198 on physicle interfaces and ip mtu 9100 on VLAN Interfaces. So I think there should be no Problem.
    • Since where using VSX icmp redirects is disabled (no icmp redirects)
    • About the mentioned TTL/hop limit: I did Packet Capture on some Uplinks, but could not see many packets with TTL below 10 - except some multicast packets.
    • show ip error is low:
      --------------------------------------------------
      Drop reason                                Packets
      --------------------------------------------------
      Malformed packets                                0
      IP address errors                              367
    • Checked Interface statistics for Drops: no TX and no  RX drops
    I´m trying to find the root cause of this, but by now I failed and would like to ask the community, if there are any hints on how to troubleshoot and find the root cause.
    Is there any way of logging that I can turn on to see why the copp is hitting on ip-exceptions or where the source of the packets are?
     
    If anyone has experience to share - you are very welcome!
     
    Thank you,
    Alex.



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  • 2.  RE: High COPP drops on class ip-exeptions

    Posted Mar 06, 2026 02:13 AM

    Hello,

    I want to follow this thread because I have noticed same "issue" with fw 10.13 and 10.15 in cores routing L3 (8360) and edges (6300M/F which has usually only management SVI) 

    These drops seems to not affect any data streams running in network so I would also like to know what are these "drops" anyway.



    ------------------------------
    Jori Luoto
    AV-IT Specialist
    Audico Systems oy
    AV-IT specialist
    Audico Systems oy
    ------------------------------



  • 3.  RE: High COPP drops on class ip-exeptions

    Posted Mar 19, 2026 04:16 AM

    Yesterday, I opened a TAC Case on this. I will provide updates here.

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  • 4.  RE: High COPP drops on class ip-exeptions

    Posted Mar 24, 2026 01:54 PM

    Any updates?

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  • 5.  RE: High COPP drops on class ip-exeptions

    Posted Mar 25, 2026 03:44 AM

    I´m still in contact with TAC. The first level support-engineer couldn´t find the cause, therfore the case is escalated to the next level support-engineer. 

    As soon as I get any specific infos I will give an update here. 

    My I ask if you see something similar in your infrastructure?

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  • 6.  RE: High COPP drops on class ip-exeptions

    Posted Mar 25, 2026 09:01 AM

    Yes, I'm seeing this issue.  High number of copp drops due to ip-exceptions.  The only out-of-the-ordinary factor is that we're seeing this in vlans with IDs above 4000.




  • 7.  RE: High COPP drops on class ip-exeptions

    Posted Mar 26, 2026 03:43 AM

    Those alerts recently appeard for one of my deployement. And while the switch had no SVI working.  I wonder if it's an alert flagged because of a specific firmware. It's my only site using FW 10.16.1020

    No other sites use that firmware and flags this alert. 

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  • 8.  RE: High COPP drops on class ip-exeptions

    Posted Mar 26, 2026 04:28 AM

    Hello,

    At the moment I have sites running 10.13.1070 and 10.15.1030 fw's and both reports excessive ip-exception drops so problem seems to be in multiple firmwares.

    One common thing between my sites are media streams (Dante/Ravenna/NDI/etc..) and there is quite a lot of multicast there.
    I haven't have real problems which would be visible in media streams but I tuned up "class igmp" to not have that much "drops" there in igmp class.

    I would like to know how can I monitor which packets copp process reports to drop and should it affect to L2 traffic between ports or does copp just protect cpu and passes traffic  as-is?



    ------------------------------
    Jori Luoto
    AV-IT Specialist
    Audico Systems oy
    ------------------------------



  • 9.  RE: High COPP drops on class ip-exeptions

    Posted Mar 27, 2026 10:57 AM

    Hello,

    I want to share the status of this issue.
    Yesterday I had a remote sesseion with TAC-Engineer and we did some deeper troubleshooting and packet capture on shell of the switch.
    The Engineer assisted in tacking packet captures that only include packets that are hitting the copp class ip-exceptions so we are able to find the source of the packets.
    It turned out that packets arriving with TTL=1. All of them were some kind of multicast packets coming from our AMX/NDI/Dante Devices. We also saw a few packets coming from Wifi-devices in our Guest Wifi which are using mDNS.

    The point is: although the packets are counted as "dropped" in the copp statistics (because they have TTL of 1) the packets are actually NOT dropped. This explains why we don´t have any issues regarding performance.
    I mentioned to the TAC-Engineer, that this behavior (packets are statistically reported as dropped although there are NOT dropped) is not what I would expect and if it is possible to open some kind of bug-report that this is corrected in future releases. He told me, that this already happend and was reviewed but it was considered as designed and changes will not be possible at this stage.

    The clue for me is: although the copp statistics show dropped packets there are actually NO packets dropped. I will keep that in mind if I come accross a similiar behavior (maybe in another copp class).

    Alex

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  • 10.  RE: High COPP drops on class ip-exeptions

    Posted Mar 27, 2026 12:30 PM

    Hello,

    Kind of great news that drops are not "real drops" 👍

    Usually PTPv1 and Dante discovery streams (224.0.0.230-232) are TTL=1 stuff and some of NDI devices default TTL is also 1 but while drops are in L2 devices it does not make sense that L2 device reports such packets.



    ------------------------------
    Jori Luoto
    AV-IT Specialist
    Audico Systems oy
    ------------------------------



  • 11.  RE: High COPP drops on class ip-exeptions

    Posted Mar 31, 2026 09:15 AM

    I´m not sure but it could be because the 6300 is a capable L3 switch, that could cause that, although the switch is doing only L2.
    But it is just a guess.

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