Loopback - H3C S5120-SI Series Command Reference Manual

Use the undo jumboframe enable command to prevent jumbo frames from passing through an
Ethernet port.
By default, the device allows frames no larger than 10240 bytes to pass through an Ethernet port.
Examples
# Enable jumbo frames to pass through all the Ethernet ports.
<Sysname> system-view
[Sysname] jumboframe enable

loopback

Syntax
loopback { external | internal }
View
Ethernet port view
Default Level
2: System level
Parameters
external: Enables external loopback testing on an Ethernet port.
internal: Enables internal loopback testing on an Ethernet port.
Description
Use the loopback command to perform loopback testing.
Ethernet port loopback testing should be enabled while testing certain functionalities, such as
during the initial identification of any network failure.
While enabled, Ethernet port loopback testing will work in full-duplex mode. The interface will return
to its original state upon completion of the loopback testing.
Loopback testing is a one-time operation, and is not recorded in the configuration file.
Examples
# Enable loopback testing on GigabitEthernet 1/0/1.
<Sysname> system-view
[Sysname] interface gigabitethernet 1/0/1
[Sysname-GigabitEthernet1/0/1] loopback internal
Loop internal succeeded!
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