Symptom
CRC and RUNT errors are noticed on 100G Line card on ASR9k platform
This issue is also noticed during a loopback test.
Reliability is 1 due to high number of RUNT drops.
Conditions
CRC and RUNT errors are noticed to increase on the 100G port of Octane Line Card which shows reliability as 1/255
Snippet from output
#sh int Hu0/X/0/0
HundredGigE0/2/0/0 is up, line protocol is up
reliability 1/255, txload 0/255, rxload 0/255 <<<<<Reliability 1/255
sh controllers np counters np0 location 0/X/CPU0 | in RUNT
1096 DROP_FRM_RUNT
Workaround
Reset PHY by changing transport mode LAN -> OTN -> LAN
Further Problem Description
Clock to PCS block of PHY overflows which causes packet corruption and resulting CRC error on NP. Loopback setting in PHY has clock changing implementation which required a reset followed by.
