Loopback Interface; Show System-Time - TP-Link JetStream TL-SL3452 Reference Manual

the connection between the switch and the destination device is failed to
establish:
TL-SL3428#tracert 192.168.0.131 –h 20

loopback interface

Description
The loopback interface command is used to test whether the port is available
or not.
Syntax
loopback interface { fastEthernet port | gigabitEthernet port } { internal |
external }
Parameter
port —— The Fast/Gigabit Ethernet port number.
internal | external —— Loopback Type. There are two options: "internal" and
"external".
Command Mode
User EXEC Mode and Privileged EXEC Mode
Example
Do an internal-type loopback test for Gigabit Ethernet port 25:
TL-SL3428# loopback interface gigabitEthernet 1/0/25 internal
Do an external-type loopback test for Gigabit Ethernet port 25:
TL-SL3428# loopback interface gigabitEthernet 1/0/25 external

show system-time

Description
The show system-time command is used to display the current system time
and its source.
Syntax
show system-time
TL-SL3428/TL-SL3452
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JetStream L2 Managed Switch CLI Guide