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6.10.
Loop Detection
Loop detection is designed to handle loop problems on the edge of your network. This can
occur when a port is connected to a Switch that is in a loop state. Loop state occurs as a
result of human error. It happens when two ports on a switch are connected with the same
cable. When a switch in loop state sends out broadcast messages the messages loop back
to the switch and are re-broadcast again and again causing a broadcast storm.
The difference between the Loop Detection and STP:
Loop Detection STP
The loop detection function sends probe packets periodically to detect if the port connect
to a network in loop state.
The Switch shuts down a port if the Switch detects that probe packets
loop back to the same port of the Switch.
Loop Recovery:
When the loop detection is enabled, the Switch will send one probe packets every
two
seconds and then listen this packet. If it receives the packet at the same port, the Switch
will disable this port. After the time period,
recovery time
,
the Switch will enable this port
and do loop detection again.
The Switch generates syslog, internal log messages as well as SNMP traps when it shuts
down a port via the loop detection feature.
6.10.1.
CLI Configurations
Node
Command
Description
enable
show loop-detection
This command displays the current loop
detection configurations.
enable
configure terminal
This command changes the node to
configure node.
configure loop-detection (disable|enable) This command disables / enables the
loop detection on the switch.
configure loop-detection address
MACADDR
This command configures the
destination MAC for the loop detection
special packets.