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Process Switching and Fast Switching

I got a advise from a CCNP and it said that the encryption and compression are generally switched at processor level. For others such as ACLs, CBWFQ and Accounting, will the first packet is always consider in process switched ? Then, is it true if the fast switching is enabled, a cache entry is built and used for subsequent packets. If all fast switching paths are disabled, then every packet is switched by the processor. Thus, how am I going to confirm whether my routers fast swithcing paths are enabled all the way ? Is it by default on or must enable the CEF or others command ? Please advises.

Community Member

Re: Process Switching and Fast Switching

Try the following to determine your cache usage (From open forum):

The show ip cache command

Question: What is the sh ip cache command used for?

I am running Cisco IOS 11.1(12) on my Cisco 7500.


The sh ip cache command in the Cisco IOS is used to give details on what

Destination IP addresses/networks are recognized by the router to be utilized

in fast/autonomous/silicon switching (interrupt based) paths for IP packets,

vs. process switching (requiring explicit routing table lookups) for IP packets

that move through the router.

If you want to see the cache for optimum or flow switching paths, specify

either sh ip cache optimum or sh ip cache flow. To get a better idea

on what path packets are taking through your router at any time, use the hidden

show ip switch command.


Cisco Employee

Re: Process Switching and Fast Switching

Another thing you can look at is show int switching which will show you the switching path statistics for your interfaces. And a good URL to get some more info on switch paths is:

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