I was looking up a similar case for ASR-9001 platform IOS XR code 4.3.2 and alerts looked like below:
As I further checked on this the interface counters looked clean and there were no drops and signs of congestion/discards. All of the ingress and egress packets were forwarded in normal way and I could also see no dot1q frames were identified on the interface that may have been dropped due to wrong VLAN encapsulations as per the counter explanations from below URL:
https://hasanmansur.com/2012/12/15/layer-2-discards-troubleshooting-rx-tx-discards
“InDiscards” are almost always caused by a port that is receiving tagged frames for a VLANID that that port is not a member of.
So as per the observations the reported alarm seems false and could not be related to counters on the interfaces:
The interface stats look clean and I do not see any discards for legitimate traffic:
Statistics for interface GigabitEthernet x/x/x/x (cached values):
Ingress:
Input total bytes = 33080084
Input good bytes = 33080084
Input total packets = 184799
Input 802.1Q frames = 0
Input pause frames = 0
Input pkts 64 bytes = 67504
Input pkts 65-127 bytes = 57148
Input pkts 128-255 bytes = 36526
Input pkts 256-511 bytes = 3825
Input pkts 512-1023 bytes = 16717
Input pkts 1024-1518 bytes = 3079
Input pkts 1519-Max bytes = 0
Input good pkts = 184799
Input unicast pkts = 98431
Input multicast pkts = 28492
Input broadcast pkts = 57876
Input drop overrun = 0
Input drop abort = 0
Input drop invalid VLAN = 0
Input drop invalid DMAC = 0
Input drop invalid encap = 0
Input drop other = 0
Input error giant = 0
Input error runt = 0
Input error jabbers = 0
Input error fragments = 0
Input error CRC = 0
Input error collisions = 0
Input error symbol = 0
Input error other = 0
Input MIB giant = 0
Input MIB jabber = 0
Input MIB CRC = 0
Egress:
Output total bytes = 30648266
Output good bytes = 30648266
Output total packets = 96223
Output 802.1Q frames = 0
Output pause frames = 0
Output pkts 64 bytes = 593
Output pkts 65-127 bytes = 22117
Output pkts 128-255 bytes = 36792
Output pkts 256-511 bytes = 16198
Output pkts 512-1023 bytes = 17120
Output pkts 1024-1518 bytes = 3403
Output pkts 1519-Max bytes = 0
Output good pkts = 96223
Output unicast pkts = 95850
Output multicast pkts = 373
Output broadcast pkts = 0
Output drop underrun = 0
Output drop abort = 0
Output drop other = 0
Output error other = 0
