3Com Switch 7750 Series
Command Reference Guide — Basic Port Commands Chapter 1 Port Basic Configuration Commands
1-18
1.1.18 loopback-detection control Syntax
loopback-detection control { block | nolearning | shutdown }
undo loopback-detection control
View
Ethernet port view
Parameter
block: Specifies to block the port where loop is detected, that is, the port cannot receive
or send any packets except BPDU packets. The system will periodically detect whether
loopback still occurs on the port. If yes, the port will be blocked continuously. If not, and
no other protocols (such as STP, LACP, DLDP) change the state of the port, the port will
be restored to the state of sending and receiving packets normally.
nolearning: Specifies the port to continue forwarding packets after loopback is
detected on it. However, the port will stop learning new MAC addresses. The system
will periodically detect whether loopback still occurs on the port. If yes, the port keeps in
the current state. If not, the port will be restored to the state of sending and receiving
packets normally, and additionally the MAC address learning function will be also
restored for the port.
shutdown: Specifies to disable the port after loopback is detected on the port.
Description
Use the loopback-detection control command to set the processing mode for the port
where loopback is detected.
Use the undo loopback-detection control command to cancel the defined
processing mode for the port where loopback is detected.
By default, no processing mode is set for the port where loopback is detected.
Example
# Specify the processing mode for the port where loopback is detected as nolearning.
<3Com> system-view
System View: return to User View with Ctrl+Z.
[3Com] interface GigabitEthernet 1/0/1
[3Com-GigabitEthernet1/0/1] loopback-detection control nolearning