Symptom

Giants packets reported at 9300 switchport causing input errors on it. Topology: 9800WLC --> 9300 Switch --> SDA Network TwentyFiveGigE1/0/7 is up, line protocol is up (connected) MTU 1500 bytes, BW 10000000 Kbit/sec, DLY 10 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive not set Full-duplex, 10Gb/s, link type is auto, media type is SFP-10GBase-SR input flow-control is on, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:02, output 00:00:05, output hang never Last clearing of "show interface" counters 3d20h Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 9541000 bits/sec, 1228 packets/sec 5 minute output rate 9741000 bits/sec, 2688 packets/sec 284714254 packets input, 249496276067 bytes, 0 no buffer Received 29190 broadcasts (29190 multicasts) 0 runts, 45561 giants, 0 throttles <<<<<<<<< 45562 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored <<<<<<<< 0 watchdog, 29190 multicast, 0 pause input 0 input packets with dribble condition detected 628447652 packets output, 225539197690 bytes, 0 underruns Output 332453 broadcasts (195165 multicasts) 0 output errors, 0 collisions, 0 interface resets 0 unknown protocol drops 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 pause output 0 output buffer failures, 0 output buffers swapped out PCAPs taken at WLC reports that the only traffic truly generated by the WLC itself with >1500 looks related to sd-avc, configured as follows: avc sd-service segment AppRecognition controller address A.B.C.D destination-ports sensor-exporter 21730 dscp 16 source-interface Vlan200 transport application-updates https url-prefix sdavc

Conditions

Controller is in fabric mode. WLC Model: 9800-80 WLC Version: 17.9.5 AP Model: 9136 and 9130 AP in FlexConnect. Switch Model: C9300X-12Y, C9300-24T. Switch Version: 17.9.3

Workaround

Enable jumbo frame on 9300 switch (system mtu 9100) and all the nodes towards DNAC, then the packets would not be dropped.

Further Problem Description