I have a 3550 switch and I am wanting to look at the IP flows much like you can do on a router with issueing the show ip cache flow statement(after you have issue the ip route-cache flow statement on an interface.
When I do this in my 3550 switch, I do not see any of the flows. In fact, the active flow number is usually 0 an thus, no individual flow details are shown. I have searched through the switch documentation and do not see any information that suggests this works differently on a 3550 multilayer switch.
Even though the command is unsupported on physical interfaces of the switches, you can still apply the command to logical vlan interfaces. So if you want to monitor traffic flow on fa0/1 and it falls in vlan 2, apply the "ip route-cache flow" command under vlan 2.
Use show ip cache flow command to see the traffic flow statistics. I have tested this on a 3550 switch, and it works.
I did as you suggested but I do not see all the flows that are actually going on to anything on that VLAN. I can go to one of my main routers and look at the flows to the subnet that my vlan is associated with and see 100's of flows but when I look at the cache flows in the switch at the same time, I only see a few.
Sorry this is not very responsive as my e-mail notificaion was not working.