3Com Switch 4200G Configuration Guide

Ethernet Port Configuration Example 73
After you use the shutdown command on a port, the port cannot run loopback test.
You cannot use the speed, duplex, mdi and shutdown commands on the ports
running loopback test. Some ports do not support loopback test, and corresponding
prompts will be given when you perform loopback test on them.
Enabling the System to
Test Connected Cable
You can enable the system to test the cable connected to a specific port. The test
result will be returned in five minutes. The system can test these attributes of the
cable: Receive and transmit directions (RX and TX), short circuit/open circuit or not,
the length of the faulty cable.
The virtual-cable-test command is not available on combo ports.
Displaying and
Debugging Ethernet
Port
After the above configuration, enter the display commands in any view to display
the running of the Ethernet port configuration, and thus verify your configuration.
Enter the reset counters command in user view to clear the statistics of the port.
Ethernet Port
Configuration
Example
Network requirements
■ Switch A is connected to Switch B through trunk port GigabitEthernet1/0/1.
■ Configure the default VLAN ID for the trunk port as 100.
■ Allow the packets of VLAN 2, VLAN 6 through VLAN 50 and VLAN 100 to pass the
port.
Configure the Ethernet port to run
loopback test
loopback { external | internal } Optional
Table 55 Configure the Ethernet port to run loopback test
Table 56 Enable the system to test connected cables
Operation Command Remarks
Enter system view system-view —
Enter Ethernet port view interface interface-type interface-number —
Enable the system to test
connected cables
virtual-cable-test Required
Table 57 Display and debug Ethernet port
Operation Command Remarks
Display port configuration
information
display interface [ interface-type |
interface-type interface-number ]
You can use the
commands in any view.
Display port loopback
detection state
display loopback-detection
Display brief configuration
information about one or
all ports
display brief interface [ interface-type
interface-number ] [ | { begin | include |
exclude } string ]
Display current
type-specific ports
display port { hybrid | trunk | combo |
vlan-vpn }
Clear the statistics of the
port
reset counters interface [
interface-type | interface-type
interface-number ]
After 802.1X is enabled,
the port information
cannot be reset.