Fabric Watch Administrator's Guide v7.0.0 (53-1002153-01, April 2011)

Fabric Watch Administrator’s Guide 71
53-1002153-01
Port fencing
7
The allowed threshold configuration settings are displayed on a per-class basis. FOP_Port class
thresholds apply to the entire switch. You can set different thresholds for Storage and Host
FOP_Ports if they are on different switches, based on the fabric configuration.
Port fencing configuration
You must configure port thresholds with the portThConfig command before you can enable port
fencing using the portFencing command. See “portThConfig command procedures” on page 61 for
example port configurations, or refer to the Brocade Fabric OS Command Reference Guide for
complete inThreshold recommendations for CRC errors and Invalid Words.
You can configure a specified port type or a list of port types to enable port fencing for one or more
areas. Use the all option to indicate all port types or all areas.
Port fencing recommended area settings
Cyclic redundancy check (CRC) errors and invalid transmission words (ITW) can occur on normal
links. They have also been known to occur during certain transitions such as server reboots. When
these errors occur more frequently, they can cause a severe impact. While most systems can
tolerate infrequent CRC errors or invalid words, other environments can be sensitive to even
infrequent instances. The overall quality of the fabric interconnects is also a factor.
When establishing thresholds for CRC errors and Invalid Words, consider the following. In general,
“cleaner” interconnects can have lower thresholds as they should be less likely to introduce errors
on the links. Moderate (recommended), conservative and aggressive threshold recommendations
are provided in the table below. After selecting the type of thresholds for an environment, set the
low threshold with an action of ALERT (RASlog, e-mail, SNMP trap). The alert will be triggered
whenever the low threshold is exceeded. Set the high threshold with an action of Fence. The port
will be fenced (disabled) whenever the high threshold is detected. Aggressive threshold
suggestions do not include settings for low, and instead only have the high values to trigger fencing
actionformation on the portThConfig command.
Table 21 shows the recommended moderate, aggressive, and conservative thresholds for
supported port fencing areas.
TABLE 21 Recommended port fencing thresholds
Area Moderate/recommended
threshold
Aggressive threshold Conservative threshold
Cyclic redundancy check
(CRC)
Low 5
High 20
Low 0
High 2
Low 5
High 40
Invalid transmission word
(ITW)
Low 25
High 40
Low 0
High 25
Low 25
High 80
Link reset (LR) Defaults Low 0
High 5
Defaults
Class 3 frame discard due
to timeout (C3TX_TO)
Low 0
High 5
N/A N/A