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Jumbo frames on an 1500MTU-switchport

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  • 1.  Jumbo frames on an 1500MTU-switchport

    Posted Sep 19, 2023 11:17 AM

    Hi dear community,

    I have a problem with two customers and both are using the 8325-CX-switch.

    Some interfaces, which are configured to use a 1500 byte MTU have teir a no-zero jumbo frame counter in TX-direction!

    All those interfaces were always configured without jumbo frames. The only interface with jumbo frames enabled is LAG256 for the use with VSX (jumbo is here best practise).

    Both customers run different software-versions: 10.08.1010 and 10.10.1050.

    What is the reason for a non-zero-counter and what packets could be sent on those interfaces? Is this a bug? Can you reproduce this issue?

    One thing I need to add: Up until now I haven't had the time to collect a pcap of the outgoing interface to look for packets! Maybe there are none and the counter is buggy.

    BR

    Michael

    Example:

    Interface 1/1/1 is up

    Admin state is up

    Link state: up for 11 months (since Fri Jul 08 22:19:10 CEST 2022)

    Link transitions: 7

    Description:

    Hardware: Ethernet, MAC Address: 64:e8:81:1b:78:fd

    MTU 1500

    Type SFP+DAC1

    Full-duplex

    qos trust none

    Speed 10000 Mb/s

    Auto-negotiation is off

    Flow-control: off

    Error-control: off

    Rate collection interval: 300 seconds

    Rate                               RX                   TX        Total (RX+TX)

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

    Mbits / sec                     22.76               703.62               726.38

    KPkts / sec                      7.27                65.06                72.33

       Unicast                        7.26                65.05                72.31

       Multicast                      0.00                 0.00                 0.00

       Broadcast                      0.00                 0.01                 0.01

    Utilization                      0.23                 7.04                 7.27

    Statistic                          RX                   TX                Total

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

    Packets                  334262763928         356743594143         691006358071

       Unicast                331639312061         355764930366         687404242427

       Multicast                1573836682            123223691           1697060373

       Broadcast                1049615216            855440086           1905055302

    Bytes                 206465426058563      335774956716117      542240382774680

    Jumbos                    36721935998          77999841416         114721777414