1-8
To do… Use the command… Remarks
interface interface-type
interface-number
frames
In Ethernet
interface view
jumboframe enable
the length of 9,216 bytes to
pass through all Layer 2
Ethernet interfaces.
Enabling Loopback Detection on an Ethernet Interface
If a port receives a packet that it sent out, a loop occurs. Loops may cause broadcast storms. The
purpose of loopback detection is to detect loops on an interface.
When loopback detection is enabled on an Ethernet interface, the device periodically checks whether
the ports have any external loopback. If it detects a loopback on a port, the device will set that port to be
under loopback detection mode.
z If loops are detected on an access port, the port will be blocked. Meanwhile, trap messages will be
sent to the terminal, and the corresponding MAC address forwarding entries will be removed.
z If loops are detected on a trunk port or a hybrid port, trap messages are sent to the terminal. If the
loopback detection control function is also enabled on the port, the port will be blocked, trap
messages will be sent to the terminal, and the corresponding MAC address forwarding entries will
be removed.
Follow these steps to configure loopback detection:
To do… Use the command… Remarks
Enter system view
system-view
—
Enable global loopback
detection
loopback-detection enable
Required
Disabled by default
Configure the interval for port
loopback detection
loopback-detection
interval-time time
Optional
30 seconds by default
Enter Ethernet interface view
interface interface-type
interface-number
—
Enable loopback detection on a
port
loopback-detection enable
Required
Disabled by default
Enable loopback detection
control on a trunk port or a
hybrid port
loopback-detection control
enable
Optional
Disabled by default
Enable loopback detection in all
the VLANs to which trunk or
hybrid ports belong
loopback-detection per-vlan
enable
Optional
Enabled only in the default
VLAN(s) with trunk port or
hybrid ports
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