Extreme Networks ExtremeWare Version 7.8, Troubleshooting Manual

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90 Advanced System Diagnostics and Troubleshooting Guide
Diagnostics
Configuring the FDB Scan Diagnostics
• To set the interval between FDB scans, use the following command:
configure fdb-scan period <1-60>
The interval is a number in the range from 1 to 60 seconds. The default is 30 seconds. We
recommend a period of at least 15 seconds. If you attempt to configure a period of fewer than
15 seconds, the system displays the following warning message:
Setting period below (15) may starve other tasks.
Do you wish to do this? (yes, no, cancel) 06/19/2003 10:29:28 <INFO:SYST> serial
admin: configure fdb-scan period 1
Enter a “y” to proceed with the change; enter an “n” to reject the change.
• To configure the action taken when too many FDB scan test failures are detected within the specified
FDB scan period, use this command:
configure fdb-scan failure-action [log | sys-health-check]
If you specify the
log
option, or no auto-recovery option was specified using the
configure sys-health-check
command, the response to FDB scan failures is to log one instance of
the failure message. The default is
log
.
If you specify the
sys-health-check
option, and an
auto-recovery
option was specified using the
configure sys-health-check
command, the response to too many FDB scan failures is to take
whatever action the system health check is configured to perform.
• To configure the options for the FDB error checking function, use this command:
run fdb-check [all | index <bucket> <entry> | [<mac_address> | broadcast-mac]
{<vlan name>}] {extended} {detail}
System Impact of the FDB Scan Diagnostic
Using the default values (disabled, log, 30 seconds), the FDB Scan is a non-invasive test. But if the scan
interval is configured to less than 12 seconds, system performance might be affected, because system
processes might be starved.
NOTE
Generally, at the default 30 second FDB Scan period, it will take 30*128 seconds to scan the entire
FDB memory. Of course, for lower FDB memory locations, detection will occur earlier in the
30*128 second window. At an FDB Scan period of one second, it will take 128 seconds to scan through
the entire FDB memory, but it will consume more than 50% of CPU use during those 128 seconds.
Network Impact of the FDB Scan Diagnostic
Impact on network traffic is negligible. There might be some impact if the system health check feature
has been selected and the configured FDB Scan threshold is exceeded. The impact depends on the way
the system health check feature is configured.