This article explains about log message: DRD0 XQSS_CMERROR_DSTAT_INT_REG_DROP0_QDEPTH_UNDRN appeared on FPC and solution to resolve it.
1) Interfaces on the affected FPC may experience flapping just before the occurrence of major errors, below logs will be reported.
mib2d[75768]: %DAEMON-4-SNMP_TRAP_LINK_DOWN: ifIndex 794, ifAdminStatus up(1), ifOperStatus down(2), ifName et-0/3/2
mib2d[75768]: %DAEMON-4-SNMP_TRAP_LINK_DOWN: ifIndex 587, ifAdminStatus up(1), ifOperStatus down(2), ifName et-0/3/3
2) Major error will appear on the FPC, leading to PFE shutdown and interface administration down as below. Services will be impacted as interface remains down.
Physical interface: et-1/3/3, Administratively down, Physical link is Down
Interface index: 348, SNMP ifIndex: 794, Generation: 88012
Link-level type: Ethernet, MTU: 9192, MRU: 9200, Speed: 100Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Enabled
Pad to minimum frame size: Disabled
Device flags : Present Running Down PFE-Disabled
Interface flags: Hardware-Down Down SNMP-Traps Internal: 0x4000
Link flags : None
CoS queues : 8 supported, 8 maximum usable queues
Schedulers : 0
Hold-times : Up 0 ms, Down 0 ms
Damping : half-life: 0 sec, max-suppress: 0 sec, reuse: 0, suppress: 0, state: unsuppressed
Current address: 88:28:fb:b5:a5:8a, Hardware address: 88:28:fb:b5:a5:8a
Last flapped : 2023-11-19 10:53:52 IST (02:58:51 ago)
Statistics last cleared: 2023-11-19 03:51:14 IST (10:01:29 ago)
3) The interface flapping failed to flush the queue, leading to the xqss error and triggering the underrun.
aftd-trio[16842]: %USER-3: [Error] JnhPlus: CosSchedNodeQueuesTrio: Failed to configure Queue nodes with baseQ:24 numQueues:^H pfeInst:4
ytchip-xqss[16840]: %USER-3: [Error] CDA: XQSS: Set Q node failed for qIndex:33
4) Below error log messages will appear on the FPC, which could result in major errors:
root[27513]: %USER-5: pfe_get_state.sh : PFE AFT Get state started - Module: (xqss), Error: (XQSS_CMERROR_DSTAT_INT_REG_DROP0_QDEPTH_UNDRN), Date/Time: (19/11/2023 05:23:40)
alarmd[75764]: %DAEMON-4: Alarm set: FPC id=150995048, color=RED, class=CHASSIS, reason=FPC 0 Major Errors
5) Device configured with high-priority scheduler:# set class-of-service schedulers <scheduler name> priority high
Please refer below PR for more details and solution.
https://prsearch.juniper.net/problemreport/PR1638410To recover instantly from this situation, please reboot the affected FPC but major errors may appear again if interfaces continuing to flap.