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  • 1.  High Output MTU

    Posted 12-14-2021 10:42
    We have MX204 that has high Output MTU under PFE statistics that just rebooted yesterday, comparing one of our MX that has been up for 8 months.

    All interfaces on both MXs doesn't have alarming MTU errors in the interfaces so I am wondering where is this coming from...

    cr1> show pfe statistics traffic | match MTU
    Packet Forwarding Engine Input IPv4 Header Checksum Error and Output MTU Error statistics:
    Input Checksum : 0
    Output MTU : 5187591
    
    cr1> show system uptime | match up
    5:12AM up 23:58, 2 users, load averages: 0.20, 0.24, 0.24​
    
    cr1>
    Packet Forwarding Engine traffic statistics:
        Input  packets:           7426694578                36958 pps
        Output packets:           7426693144                36458 pps
        Fabric Input  :                    0                    0 pps
        Fabric Output :                    0                    0 pps
    Packet Forwarding Engine local traffic statistics:
        Local packets input                 :              8152388
        Local packets output                :             16567870
        Software input control plane drops  :                    0
        Software input high drops           :                    0
        Software input medium drops         :                    0
        Software input low drops            :                    0
        Software output drops               :                    0
        Hardware input drops                :                    0
    Packet Forwarding Engine local protocol statistics:
        HDLC keepalives            :                    0
        ATM OAM                    :                    0
        Frame Relay LMI            :                    0
        PPP LCP/NCP                :                    0
        OSPF hello                 :                19756
        OSPF3 hello                :                    0
        RSVP hello                 :                36847
        LDP hello                  :                    0
        BFD                        :                   11
        IS-IS IIH                  :                    0
        LACP                       :               171749
        ARP                        :               684498
        ETHER OAM                  :                    0
        Unknown                    :                    0
    Packet Forwarding Engine hardware discard statistics:
        Timeout                    :                    0
        Truncated key              :                    0
        Bits to test               :                    0
        Data error                 :                    0
        TCP header length error    :                    0
        Stack underflow            :                    0
        Stack overflow             :                    0
        Normal discard             :           2271315474
        Extended discard           :                    0
        Invalid interface          :                    0
        Info cell drops            :                    0
        Fabric drops               :                    0
    Packet Forwarding Engine Input IPv4 Header Checksum Error and Output MTU Error statistics:
        Input Checksum             :                    0
        Output MTU                 :              5228064

    cr2> show pfe statistics traffic | match MTU
    Packet Forwarding Engine Input IPv4 Header Checksum Error and Output MTU Error statistics:
        Input Checksum             :                    0
        Output MTU                 :              5161081
    
    {master}
    cr2> show system uptime | match up
     5:16AM  up 230 days, 15:43, 2 users, load averages: 0.77, 0.47, 0.38​
    
    cr2>
    0> show pfe statistics traffic
    Packet Forwarding Engine traffic statistics:
        Input  packets:        3077832159967               129123 pps
        Output packets:        3075837726930               125731 pps
        Fabric Input  :        2389104751350                84328 pps
        Fabric Output :        2389104751354                84327 pps
    Packet Forwarding Engine local traffic statistics:
        Local packets input                 :           1890900032
        Local packets output                :           3188281114
        Software input control plane drops  :                    0
        Software input high drops           :                    0
        Software input medium drops         :                    0
        Software input low drops            :                    0
        Software output drops               :                    0
        Hardware input drops                :                    0
    Packet Forwarding Engine local protocol statistics:
        HDLC keepalives            :                    0
        ATM OAM                    :                    0
        Frame Relay LMI            :                    0
        PPP LCP/NCP                :                    0
        OSPF hello                 :             13071756
        OSPF3 hello                :                    0
        RSVP hello                 :             21459232
        LDP hello                  :                    0
        BFD                        :            254245992
        IS-IS IIH                  :                    0
        LACP                       :             39848945
        ARP                        :             14283500
        ETHER OAM                  :                    0
        Unknown                    :                    4
    Packet Forwarding Engine hardware discard statistics:
        Timeout                    :                    0
        Truncated key              :                    0
        Bits to test               :                    0
        Data error                 :                    0
        TCP header length error    :                    0
        Stack underflow            :                    0
        Stack overflow             :                    0
        Normal discard             :          13203089923
        Extended discard           :                    0
        Invalid interface          :                    0
        Info cell drops            :                    0
        Fabric drops               :                    0
    Packet Forwarding Engine Input IPv4 Header Checksum Error and Output MTU Error statistics:
        Input Checksum             :                    0
        Output MTU                 :              5160406


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    Leo Chan
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