Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 40)

10 Multi-Service IronWare Switching Configuration Guide
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Port loop detection
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Port loop detection
This feature allows the Brocade device to disable a port that is on the receiving end of a loop by
sending test packets. You can configure the time period during which test packets are sent.
Strict mode and Loose mode
There are two types of loop detection; Strict Mode and Loose Mode. In Strict Mode, a port is
disabled only if a packet is looped back to that same port. Strict Mode overcomes specific
hardware issues where packets are echoed back to the input port. In Strict Mode, loop detection
must be configured on the physical port.
In Loose Mode, loop detection is configured on the VLAN of the receiving port. Loose Mode
disables the receiving port if packets originate from any port or VLAN on the same device. The VLAN
of the receiving port must be configured for loop detection in order to disable the port.
Recovering disabled ports
Once a loop is detected on a port, it is placed in a disabled state. The port will remain disabled until
one of the following occurs:
• You manually disable and enable the port at the Interface Level of the CLI
• You enter the command clear loop-detection. The clear loop-detection command clears the
loop detection statistics and enables all disabled ports
• The device automatically re-enables the port. To set your device to automatically re-enable
disabled ports, refer to
“Configuring the device to automatically re-enable ports” .
Disable duration and loop detection interval
By default, the ports are shutdown permanently until user enables it manually. You can configure
the disable duration from 1 minute to 1440 minutes (24 hours)
By default. the Loop Detection time Interval between the loop detection BPDU is 1 second. You can
configure the loop detection PDU interval from 100ms to 10 seconds.
Configuration notes
Loopback detection packets are sent and received on both tagged and untagged ports. Therefore,
this feature cannot be used to detect a loop across separate devices.
The following information applies to Loose Mode loop detection:
• Loop detection is configured on the VLAN. Different VLANs may disable different ports. A
disabled port affects every VLAN using it.
• Loose Mode disables the receiving port if packets originate from any port or member port of a
VLAN on the same device
• The VLAN of the receiving port must be configured for loop detection in order to disable the
port.
• Loose Mode floods test packets to the entire VLAN. This can impact system performance if too
many VLANs are configured for Loose Mode loop detection.