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Tuesday, February 23, 2010

Is CEF required on access switches?

We are currently using a 4510-RE with 12.2(53) code. We are using it as access switch. During the POST of the switch, we get the following message:

% Enable CEF globally before configuring VRF on any interface

We are not sure if CEF is necessary on access switches which are not routing devices?

Cisco Express Forwarding (CEF) is advanced, Layer 3 IP switching technology, so there is no use of enabling n access-layer switches(L2).

Here are the advantages of using CEF -
  1. CEF is less CPU-intensive than fast switching route caching. More CPU processing power can be dedicated to Layer 3 services such as quality of service (QoS) and encryption.
  2. CEF offers full switching capacity at each line card when distributed CEF (dCEF) mode is active.
  3. CEF offers unprecedented level of switching consistency and stability in large dynamic networks.
In general a layer 2 switch doesnt require CEF. However if you need qos on the switch, you need to enable ip routing and cef.

Please click here to find more information on configuring QoS
Please click here to read more about when CEF is required for QoS

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