Sorry that I create another thread for the same problem, but I just want to tell that I can grab FDB info by the following commands via Snmpwalk.
May FDB table feature on Nexus 5/7K Series is doable with some special mibs?
snmpwalk -v3 -u admin -l authNoPriv -a MD5 -A password ip CISCO-VTP-MIB::vtpVlanState
snmpwalk -v3 -u admin -l authNoPriv -a MD5 -A password ip -n vlan-id BRIDGE-MIB::dot1dTpFdbAddress
snmpwalk -v3 -u admin -l authNoPriv -a MD5 -A password ip -n vlan-id BRIDGE-MIB::dot1dTpFdbPort
snmpwalk -v3 -u admin -l authNoPriv -a MD5 -A password ip -n vlan-id BRIDGE-MIB::dot1dBasePortIfIndex
snmpwalk -v3 -u admin -l authNoPriv -a MD5 -A password ip -n vlan-id IF-MIB::ifName