Software Version 2.8.1
27
Software Version 2.8.1
C613-10477-00 REV B
Limiting Rapid MAC Movement
This Software Version introduces the ability to limit rapid MAC movement.
MAC address thrashing occurs when MAC addresses move rapidly between
one or more ports or trunks. For example, certain MAC addresses are learnt on
one port, then very shortly afterwards are learnt on another port, then learnt on
the original port again, and so on. This typically occurs when there is an
uncontrolled loop on the network.
Disabling a port
There are different ways you can disable a port when thrashing is detected.
These are called thrash actions:
■
learnDisable
Address learning is temporarily disabled on the port.
■
portDisable
The port is logically disabled. Traffic flow is prevented, but the link
remains up. The device at the other end does not notice that the port has
changed status, and the link LEDs at both ends stay on. This is equivalent
to entering the
disable switch port
command.
■
linkDown
The port is physically disabled and the link is down. This is equivalent to
entering the
disable switch port link=disabled
command.
■
vlanDisable
The port is disabled only for the VLAN on which thrashing has occurred. It
can still receive and transmit traffic for any other VLANs of which it is a
member.
When a MAC address is thrashing between two ports, only one of those ports
is disabled. When multiple ports are involved, enough ports are disabled to
prevent the storm.
To set a thrash action for a port, use the command:
set switch port={port-list|all}
[thrashaction={learndisable|linkdown|none|portdisable|vla
ndisable}]
To view the thrash action that is set for a port, use the command:
show switch port={port-list|all}
To set a thrash action for a trunk, use one of the commands:
create switch trunk=trunk [port=port-list]
[thrashaction={learndisable|linkdown|none|portdisable|vla
ndisable}]
set switch thrashlimit=trunk
[thrashaction={learndisable|linkdown|none|portdisable|vla
ndisable}]
To view the thrash action that is set for a trunk, use the command:
show switch trunk={trunk}
