Configuring Port Guard - Cisco AP776A - Nexus Converged Network Switch 5020 Configuration Manual

Fibre Channel Interfaces
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m

Configuring Port Guard

Using the port guard feature, you can restrict the number of error reports and bring a malfunctioning port
to down state dynamically. The link failure can be caused by the following reasons:
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The port guard feature is intended for use in environments where the system and application environment
does not adapt quickly and efficiently to a port going down and back up, or to a port rapidly cycling up
and down, which can happen in some failure modes. For example, if a system takes five seconds to
stabilize after a port goes down, but the port is going up and down once a second, this might ultimately
cause a more severe failure in the fabric.
The port guard feature gives the SAN administrator the ability to prevent this issue from occurring in
environments that are vulnerable to these problems. The port can be configured to stay down after the
first failure, or after specified number of failures in specified time period. This allows the SAN
administrator to intervene and control the recovery, avoiding any problems caused by the cycling.
To enable or disable the port guard for a port, follow these steps:
Command
Step 1
switch# config t
Step 2
switch(config)# interface fc1/1
Step 3
switch(config)# errdisable detect cause
link-down
switch(config)# errdisable detect cause
link-down [num-times number duration
seconds]
switch(config)# no errdisable detect cause
link-down
Note Even if the link does not flap due to failure of the link, and port guard is not enabled, the port goes into
a down state if too many invalid FLOGI requests are received from the same host. Use the shut and the
no shut commands consecutively to bringup the link.
This example shows how to configure port guard to bring a port to down state if the link flaps 5 times
within 30 seconds:
Switch# config t
Switch (config)# interface fc1/1
Cisco MDS 9000 Family CLI Configuration Guide
13-16
General link failure.
Link failure due to loss of signal (LOS) or not operational (NOS).
High bit error rate.
Too many interrupts.
Cable is disconnected.
BB_credit buffers overflow.
Hardware recoverable errors.
The connected device rebooted (F ports only).
The connected linecard rebooted (ISL only).
Chapter 13
Purpose
Enters configuration mode.
Selects the port interface.
Brings the port to down state if the link flaps
once.
Brings the port to down state if the link flaps for
the number of instances within the specified
seconds.
Removes (default) the port guard configuration
for the interface. The link resumes flapping and
sending error reports normally.
OL-18084-01, Cisco MDS NX-OS Release 4.x
Configuring Interfaces