I can read switches(not config VLAN) MAC table successful through MIB
table:
dot1dTpFdbTable "1.3.6.1.2.1.17.4.3".

If VLAN configed, I use communitystring@VLANNUM to read MAC table from
cisco switches.
strange problem occur! All mac entries are map to a port that switches
connect to each other.
So, one port maybe has hundreds entry, but others have none!

Environment:
four C2950 and one C3548 connect two WS-C6506 as backup link.
17 vlans conifged, some ports use port-channel.