Jozef Janitor wrote a highly relevant comment to my post on CEF accounting: enabling it on a Catalyst switch drastically reduces its performance. The impact of CEF accounting (or other forwarding plane features) depends on switching implementation:
- There is almost no impact on single-CPU software platforms; the router has to perform CEF lookup anyway and increases the CEF accounting counters on-the-fly;
- Distributed software platforms are more complex, as the central CPU has to (at the very least) collect the switching statistics.
- The impact on hardware platforms is dependent on the layer 3 lookup implementation