Hi
Interface bandwidth requirements is necessary if we´re talking about a very larger amount of traffic, othewise, it is not a problem.
According to Cisco docs, Those are de prerequisites and restriction. If your 3750 is Layer 2 only, it will be a problem.
Prerequisites for Configuring NetFlow Top Talkers
Before you enable NetFlow and NetFlow Top Talkers, you must:
Configure the router for IP routing
Ensure that one of the following is enabled on your router, and on the interfaces that you want to configure NetFlow on: Cisco Express Forwarding (CEF), distributed CEF, or fast switching
Understand the resources required on your router because NetFlow consumes additional memory and CPU resources.
Restrictions for Configuring NetFlow Top Talkers
Cisco IOS Releases 12.2(14)S, 12.0(22)S, or 12.2(15)T
If your router is running a version of Cisco IOS prior to releases 12.2(14)S, 12.0(22)S, or 12.2(15)T the ip route-cache flow command is used to enable NetFlow on an interface.
If your router is running Cisco IOS release 12.2(14)S, 12.0(22)S, 12.2(15)T, or later the ip flow ingress command is used to enable NetFlow on an interface.
Cisco IOS Release 12.2(33)SXH
Some of the keywords and arguments for the commands used to configure the NetFlow MIB and Top Talkers feature are not supported in 12.2(33)SXH. See the syntax descriptions for the commands in the command reference (U
