• You might observe slow file transfer speeds via SCP and IPERF for example to a particular member of a virtual-chassis.
• The Master member exhibits slow file transfers and moving connections to another member alleviates the issue.
• Tests go from end to end host systems. If the host terminates on affected FPC, a slow transfer is observed. Nonetheless, moving the same cable to another FPC and the transfer goes fast.
• No evident drops or error entries in the logs.
• SNMP walks ran to the VC periodically timeout.
• No issues observed for CPU, memory or load when testing.

Example of a SNMP walk ran against the switch shows a timeout:

% snmpwalk -v2c -c xxxxx 10.0.0.1

SNMPv2-MIB::sysDescr.0 = STRING: Juniper Networks, Inc. ex4300-48t Ethernet Switch, kernel JUNOS 21.4R3-S7.6, Build date: 2024-04-20 11:44:44 UTC Copyright (c) 1996-2024 Juniper Networks, Inc.
SNMPv2-MIB::sysObjectID.0 = OID: SNMPv2-SMI::enterprises.2636.1.1.1.2.63
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (58944566) 6 days, 19:44:05.66
SNMPv2-MIB::sysContact.0 = STRING:
SNMPv2-MIB::sysName.0 = STRING: switch
SNMPv2-MIB::sysLocation.0 = STRING:
SNMPv2-MIB::sysServices.0 = INTEGER: 6
IF-MIB::ifNumber.0 = INTEGER: 477
IF-MIB::ifIndex.4 = INTEGER: 4
Timeout: No Response from 10.0.0.1

Make sure to double check the vc-ports statistics with the command:

> show virtual-chassis vc-port statistics extensive

In this example the vc-port vcp-255/1/0 (et-0/1/0) seems to exhibit a hardware problem:

fpc0:
--------------------------------------------------------------------------
                          RX                    TX
Port: vcp-255/1/0
Total octets:             469564050598          11970935922
Total packets:            1736082037            19548827
Unicast packets:          1722176107            11437069
Broadcast packets:        13609184              8067961
Multicast packets:        296746                43797
MAC control frames:       0                     0
CRC alignment errors:     52821870
Oversize packets:         0
Undersize packets:        0
Jabber packets:           0
Fragments received:       460816

Replacing this DAC cable between two of the members resolved the issue.