H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 120)

14-7
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If loops are detected on a port that is of trunk or hybrid type, 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 port view
interface interface-type
interface-number
—
Enable loopback detection on the
port
loopback-detection enable
Required
Disabled by default
Enable loopback detection control
on the port (Trunk or Hybrid) loopback-detection control
enable
Optional
Disabled by default
Enable loopback detection in all
the VLANs containing the port loopback-detection
per-vlan enable
Optional
Enabled only in the default VLAN(s) with
Trunk port or Hybrid ports
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Loopback detection on a given port is enabled only after the loopback-detection enable
command has been issued in both system view and the port view of the port.
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Loopback detection on all ports will be disabled after the issuing of the undo loopback-detection
enable command in system view.
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If the system detects loopback in multiple VLANs on a port in a detection interval, it sends only one
trap to the terminal rather than one trap per VLAN.
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The aggregation port can not support loopback detection.
Configuring the Cable Type for an Ethernet Port
Two types of Ethernet cables can be used to connect Ethernet devices: crossover cable and
straight-through cable. To accommodate these two types of cables, an Ethernet interface on a device
can operate in one of the following three Medium Dependent Interface (MDI) modes:
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Across mode, where the Ethernet interface only accepts crossover cables.
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Normal mode, where the Ethernet interface only accepts straight-through cables.
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Auto mode, where the Ethernet interface accepts both straight-through cables and crossover
cables.
Normally, the auto mode is recommended. The other two modes are useful only when the device
cannot determine the cable type.