[nsp] 3550 not learning MAC addresses?

[John Osmon]

I've got a 3550-24-EMI running 12.1.8EA1c that isn't learning MAC
addresses, and thus flooding unicast packets to ports it shouldn't.
Static MAC assignments work fine, and manage to stem the floods, but it
isn't an ideal situation.  (Call me picky, but I like my bridges to
*learn* which stations are where...)

The VLAN in question only has 6 stations, with most of the traffic
passing between two routers at roughly 40Mbps.  One station is
a Cisco 2511, and its 10Mbps ethernet port gets overrun without
the static MAC assignments.

I don't expect many changes on this segment, so static MACs are
an OK workaround, but I really want to find out *why* this is
occurring.  I see no obvious misconfigurations, and googling hasn't
turned up much of use.  Anyone here have any ideas?