Show Interfaces Stats command

[Craddockc]

Community,

I was hoping someone could break down the output of the "show interfaces stats" command for me. I typically use this command to see if there has been any action on an interface at any point during the switches uptime. However, I cannot find any documentation on what the "Chars" output relates to. What does "Chars" mean? Im also slightly confused on the switching paths Hardware vs Route Cache vs Processor.

Im assuming that Hardware means the # of packets (frames?) switched in the hardware ASICS and Route Cache means the # of Packets (Frames?) switched using CEF or some other hardware based routing/switching mechanism? But if so, doesnt CEF use the hardware ASICS? Isnt that the whole point of it? Processor Im assuming means Packets (Frames?) punted to the L3 Processor for further processing because it couldnt be otherwise hardware switched?

Thanks for any help you can provide.

GigabitEthernet7/12
Switching path Pkts In Chars In Pkts Out Chars Out
Processor              0          0            0                0
Route cache          0          0            0                0
Hardware               0          0            0                0
Total                       0          0            0                0

[Jon Marshall]

Hardware is how many packets forwarded using ASICs rather than main CPU. These packets will CEF switched ie. CEF is a way of optimising lookups it is not tied to hardware or software but used by both

Route cache will simply be fast switching ie. the first packet is process switched (handled by the main CPU) and an entry for that flow is cached and then subsequent packets for the same flow use the cached entry.

Process switched means every packet forwarded by main CPU.

Obviously on a hardware device you would expect to see the majority of packets switched in hardware.

Jon

[Craddockc]

Jon,

Thanks for your reply and confirming what I thought. So to be precise, Hardware means any packets that were hardware switched either by CEF of Fast Switching or otherwise? And Route Cache refers to packets that were routed using flow based switching vs topology based switching (CEF)? 

Any idea what "Chars" mean? Thanks.

[Jon Marshall · Accepted solution]

As far as I know all hardware switched packets use CEF. To be honest on a modern hardware device I wouldn't expect to see any fast switched packets really although you may well see process switched for certain packets.

Route cache or fast switching was the predecessor to CEF so yes to what you say.

As for Chars I always assumed Characters although now I come to think of it not actually sure what that means :)

Sorry, perhaps someone else can explain.

Jon

[Craddockc]

Jon,

No worries. I really appreciate the input. Thanks for the clarification.