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A little confused.. When trouble shooting excessive output drops on a 3750 i noticed that al switching is done by cpu instead of "route cache". This 3750 has no ip routing enabled and no ip cef (ip cef is only for layer 3 i believe)..

But why isnt this switch using fast switching? I always thought that the first packet was processed by cpu but then it should do switching out of the learned/cached table e.g. fast switching.. But when i issue the command sh interface x/x stats the output is telling me that all packets are forwarded by CPU and none by "route cache"

?

  • The answer i posted answers your question but does not help resolve your issue. I would suggest starting a different question or a chatroom with me and I can help you troubleshoot the output drops ( im rather good at tshooting OQD) – John Kennedy Nov 25 '13 at 20:05
  • actually i created a room called "helping user209 troubleshoot" in the chat. Please join at your convenience and i can assist you – John Kennedy Nov 25 '13 at 20:08
  • We need to see your config as well as the output of sh proc cpu sort when the problem is happening – Mike Pennington Nov 26 '13 at 2:54
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 8 '17 at 15:13
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If "IP routing" is disabled then your frames are NOT getting forwarded by your CPU. I am familiar with the output that you are talking about though.

The "show interfaces _ X/X stats" is a hidden command in IOS and as such it really isn't maintained the way most other show commands are.

If you do a "show proc cpu sorted | in Input" then you will see the "IP Input" process. That is the best way that you can see how much of a tax the forwarding plane is putting on your CPU.

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  • 1
    Note: stats has not been a hidden option for a long time. – Ricky Beam Nov 25 '13 at 21:49

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