CEF and the CPU

[GRANT3779]

If we have cef running and a packet comes in where we have a fib and adjacency entry for the destination, is the cpu used at all in the forwarding process? How does the device look into the fib/adjacency table, as in what resources are utilised to carry out these lookups?

[Richard Burts · Accepted solution]

The real answer to your question will depend on which platform you are asking about. For some platforms the answer will be that the fib and adjacency table lookup is done in hardware. I would guess that the answer that you are looking for is that in some platforms the table lookup for fib and adjacency is done using CPU resources. But even in platforms where the table lookup is done with CPU the CEF lookup and processing is still much more efficient than the process switching path.

HTH

Rick 

[GRANT3779]

Rick, thanks 

Your answer clears up the few uncertainties I had with this. Appreciated.

[Richard Burts]

You are welcome. You are a frequent participant in the forum and I am glad that my answer was helpful to you.

HTH

Rick