Technical information

AX Series L2 Loop Detection Configuration Guide (Edition 2)
Copyright © 2008, 2010, ALAXALA Networks Corporation. All rights reserved.
8
(2) Operation
In L2 loop detection, an L2 control frame for detecting an L2 loop (an L2 loop detection frame) is sent
regularly from the port (a physical port or a channel group) specified in the configuration section. If the frame
returns to the sending device, the functionality determines that a loop failure has occurred.
Figure 1.4-2 Loop failure on a hub under a device - the flow of a detection frame
Behaviors after a loop failure is detected are as follows depending on the configuration specified for the port.
Table 1.4-1 Configuration types of the L2 loop detection functionality for each port
Configuring ports L2 loop
detection
frame sending
Behavior at receipt of an L2 loop detection frame
send-inact-port
Yes Detects L2 loops (log display) and blocks ports.
send-port
Yes Only detects L2 loops (log display).
uplink-port
No Detects L2 loops (log display) only for the applicable port.
Behavior according to the source settings at the source port
#1
trap-port
No Only detects L2 loops (log display).
exception-port
No None
#1: For example, if send-inact-port is set to the source port, the source port is blocked.
(3) Description of configuration parameters
Table 1.4-2 Configurations related to the L2 loop detection functionality
Parameter Description
Configured in global configuration mode (config)
loop-detection enable
Enables the L2 loop detection functionality of the device.
loop-detection
auto-restore-time
Releases (act) a blocked (inact) port automatically after a
certain period of time.
loop-detection
interval-time
Sets the sending interval of L2 loop detection frames.
loop-detection threshold
Sets the number of L2 loop detection frames receivable until the
port is blocked. If the threshold number of frames is received
during the period of time specified by loop-detection
hold-time after an L2 loop detection, the port is blocked.
loop-detection hold-time
Sets the retention time for the number of L2 loop detection frames
received until the port is blocked. The number of L2 loop detection
frames received is reset after the time specified by hold-time
has passed after an L2 loop detection.
Configured in interface configuration mode (config-if)
loop-detection
Sets the L2 loop detection frame sending or receiving behavior.
Any of the following can be specified: send-inact-port,
send-port, uplink-port, and exception-port
If this parameter is not set, trap-port is applied.
Switch
Receipt of L2 loop detection frame
-> Detection of L2 loop
Sending L2 loop
detection frame
Small-scale hub, etc.
Incorrect connection