Technical information

AX Series L2 Loop Detection Configuration Guide (Edition 2)
Copyright © 2008, 2010, ALAXALA Networks Corporation. All rights reserved.
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1.2 L2 loop control functionality
The AX series has the following functionality for preventing L2 loops:
Auto MDI/MDI-X suppression
Prevents L2 loops by creating no link-ups even with incorrect connections between access ports. This is
applicable only to twisted pair straight cables.
L2 loop detection functionality
Prevents L2 loops by detecting L2 loops in a device and blocking the port.
In addition to loops that close within the device, the detection of loops via upstream networks is also
possible.
Storm control
Restricts the receiver bandwidth of frames to a certain value when a storm occurs due to an L2 loop or
other cause, so that the impact on other communication can be minimized.
The following subsections describe the details of each functionality.
1.3 Auto MDI/MDI-X suppression
(1) Functionality overview
Auto MDI/MDI-X refers to a functionality that automatically switches the MDI/MDI-X of a port in order to
eliminate any issues resulting from the different combinations of sending/receiving types (MDI/MDI-X) and
twisted pair cable types (straight/crossover) used for lines when a 1000BASE-T port interface is used. The Auto
MDI/MDI-X suppression functionality is used to suppress Auto MDI/MDI-X functionality, and uses only MDI-X
in order to prevent loops caused by twisted-pair straight cables.
Using a crossover cable causes a loop even if the Auto MDI/MDI-X suppression functionality is used. If a
1000BASE-X port interface is used, this functionality is disabled.
(2) Description of the configuration and the parameter
Parameter Description
Configured in interface configuration mode (config-if)
no mdix auto
Disables the port's automatic MDIX functionality so that MDI-X is always used.