Features not supported by CEF - Punted or dropped ?

[Sherif Ismail]

Hello

   What are the features that are not supported by CEF ?

In this case are they dropped or punted to next switching level ?

Also when do packets will be dropped If punted to next switching level ?

In below command, why do "Encap_fail" & "Unsupported" are dropped instead of being punted ?

CEF Drop Statistics
Slot  Encap_fail  Unresolved Unsupported    No_route      No_adj  ChkSum_Err
RP             200           0           0                 11                     0           0
R2#

Many thanks

[paolo bevilacqua]

CEF supports the most important features. There is no exact list published.

Packets are never "punted to next switching level". They may be queued for process switching, and that's it.

In your example below packets are dropped because router can't do anything with a packet in lack of ARP entry, or no route to destination.

[Sherif Ismail]

Thanks Paolo for your reply

I was confused cause some cisco documents mention that some features are not suporeted by CEF as NAT & PBR

Most probably they are old documents & were not updated

http://www.cisco.com/en/US/docs/ios/11_2/feature/guide/cef.html#wp6904

thanks

[paolo bevilacqua]

You are welcome. Please remember to rate useful posts clicking on the stars below.

[milan.kulik]

Hi,

it's explained here:

http://www.cisco.com/en/US/docs/ios/12_3/switch/command/reference/swi_n1.html#wp1115470

"Encap_fail: Indicates the number of packets dropped after exceeding the limit for packets punted to the processor due to missing adjacency information (CEF throttles packets passed up to the process level at a rate of one packet per second).

Unsupported: Indicates the number of packets fast-dropped by CEF (drop adjacency)." - This is a little confusing, I'd say, but IOS command outputs sometimes are. Use  "sh ip cef adjacency drop" to see your drop adjacencies.

HTH,

Milan