HP Cisco Nexus 5000 Cisco MDS 9000 Family CLI Configuration Guide - Release 4. - Page 342

Fibre Channel Interfaces Chapter 13 Configuring Interfaces Send documentation comments to [email protected] 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: • 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). 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: Step 1 Step 2 Step 3 Command switch# config t switch(config)# interface fc1/1 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 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. 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 13-16 Cisco MDS 9000 Family CLI Configuration Guide OL-18084-01, Cisco MDS NX-OS Release 4.x