Fdb Scan; Usage Guidelines - Extreme Networks BlackDiamond 6804 Troubleshooting Manual

FDB Scan

The FDB Scan diagnostic test addresses the possibility of hardware FDB memory issues where FDB
hardware table entries do not match what was written to them by software.
The test is a non-invasive test that scans the entire FDB RAM memory pool on all switch fabrics,
compares existing software table entries against what is in the hardware table, and reports or otherwise
acts on any discrepancies it detects.

Usage Guidelines

The FDB scan diagnostic test can be run on demand by a user through the
command, or it can be configured to run as a background process in the system health checker.
You can scan the FDB on a stand-alone switch, or scan on a slot-by-slot or backplane basis on a modular
switch. Using the
check configuration.
Depending on which version of ExtremeWare you are using, the FDB scan diagnostic is either enabled
by default or disabled by default. For ExtremeWare 6.2.2b108, the default for the FDB scan is enabled.
For ExtremeWare 6.2.2b134 or later, the default for the FDB scan diagnostic is disabled.
If you load your saved ExtremeWare 6.2.2b108 configurations on a switch with ExtremeWare 6.2.2b134
or later, the FDB scan diagnostic is enabled. If you want the FDB scanning feature disabled, you must
manually disable FDB scanning.
To determine whether you have FDB scanning enabled and what failure action the switch will take in
the event of an error, use the
For empty memory locations, data is written to those sites and then read back, checking for consistent
values. Inconsistency between writing and reading indicates a corrupt bit.
Used memory locations are compared against data stored in the software tables. If the comparison is
inconsistent, the bit is deemed faulty. Upon detecting a faulty bit of memory, the test function maps out
the bit so that it is not used in future forwarding decisions. Table entries that require extensive
rebuilding are marked as suspect.
If you enable the FDB scan diagnostic and the system health checker, a section of the FDB memory on
each module's switching fabric undergoes a non-invasive check that compares it to the software copy of
the FDB. If the diagnostic detects a suspect entry, the system health checker takes one of the following
actions:
• If the suspect entry is not in use: Remap around it.
• If the suspect entry is in use, but can be removed safely (most MAC and IP-DA entries): Remove the
suspect entry and allow the table to be rebuilt naturally.
• If the entry is in use and cannot be removed safely (MAC_NH, IPSA, IPMCDA, IPDP, IPSP, or
IPXSN): Write a warning message to the log.
The failure action that the FDB scan test performs depends on the
configuration. The command configurations options available under the system health check are
described in "Health Check Functionality" on page 70.
Advanced System Diagnostics and Troubleshooting Guide
command is independent of, and does not affect, the system health
enable fdb-scan
show switch
command.
sys-health-check
FDB Scan
CLI
enable fdb-scan
command
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