In case somebody has the same issue:
… Nothing showed up in “FDB Table” for my C9x"-devices.
./discovery.php -h <HOSTNAME> -m fdb-table -d
showed several
Reason: authorizationError (access denied to that object)
The debugging output also showed that the snmpbulkwalk behind “discovery.php” included the option “-n vlan-XXX”.
Well I did not define these contexts intentionally, but a
show snmp context
listed them …
So I added a line to my IOS XE devices SNMPv3 configuration:
snmp-server group myGroup v3 priv context vlan- match prefix
(notice: This is an additional line in config. snmp-server group myGroup v3 priv I had already there)
Now the debug-discovery looked well and also the FDB Table filled up.
I had never seen this issue on other C9x switches some time ago… this is why was new to me.
Maybe this info helps others 