[c-nsp] 3550 high cpu & process switched traffic

[Tassos Chatzithomaoglou]

I guess it's normal for CDP/Spanning-Tree/PAgP/ARP/VTP/Other(?) to be switched by the cpu 
(regardless of L2/L3 operation) on a 3550, but i don't think this should happen for IP too.

I checked 2 other 3550s and i can't even find a single IP byte on any interface being forwarded on 
the egress direction using a "non-cpu" path, so i guess this must be not supported on it.

Jon Lewis wrote on 18/8/2006 20:31:
> I just checked several of ours (3550-48s), and we also seem to be 
> process switching most traffic, but the CPU load is negligible (4%).  I 
> have to wonder if this is counter buggery.  Even ones that are strictly 
> being used as L2 switches show all traffic (input and output) as process 
> switched. The ones doing a mix of L2/L3 show some traffic route cache 
> switched, but mostly processor switched.
> 
> On Fri, 18 Aug 2006, Rodney Dunn wrote:
> 
>> Something is wrong.
>>
>> What is the config?
>>
>> I'm not too good with the 3550 as that is a L3 capable switch.
>>
>> But usually it's a feature of some sort configured causing it.
>>
>> On Fri, Aug 18, 2006 at 07:44:36PM +0300, Tassos Chatzithomaoglou wrote:
>>> I have a 3550 (12.1(22)EA8) which is constantly showing high cpu usage :
>>>
>>> 3550#sh proc cpu
>>> CPU utilization for five seconds: 99%/96%; one minute: 97%; five 
>>> minutes: 97%
>>>
>>> If i'm not wrong, most of it is due to interrupts and i'm trying to 
>>> find out what exactly is causing
>>> this. The 3550 has 3 SVIs (1 for management), 6 routed interfaces (5 
>>> of them have mls qos
>>> configured) and 2 L2 interfaces (one is trunk).
>>>
>>> Also I would like to ask if the following output (only processor used 
>>> for eggress traffic on ALL
>>> interfaces) is considered normal for 3550 switches:
>>>
>>> 3550#sh int stats
>>> Vlan1
>>>            Switching path    Pkts In   Chars In   Pkts Out  Chars Out
>>>                 Processor        179      12172        179      10740
>>>               Route cache          0          0          0          0
>>>                     Total        179      12172        179      10740
>>> Vlan4
>>>            Switching path    Pkts In   Chars In   Pkts Out  Chars Out
>>>                 Processor       2806     179584       2806     168360
>>>               Route cache       8295     581139          0          0
>>>                     Total      11101     760723       2806     168360
>>> Vlan10
>>>            Switching path    Pkts In   Chars In   Pkts Out  Chars Out
>>>                 Processor   21993427 2785897656   20910415 2025707486
>>>               Route cache 2289603255 1233480520          0          0
>>>                     Total 2311596682 4019378176   20910415 2025707486
>>> Interface FastEthernet0/1 is disabled
>>>
>>> FastEthernet0/2
>>>            Switching path    Pkts In   Chars In   Pkts Out  Chars Out
>>>                 Processor          0          0     718962  112668280
>>>               Route cache          0          0          0          0
>>>                     Total          0          0     718962  112668280
>>> FastEthernet0/3
>>>            Switching path    Pkts In   Chars In   Pkts Out  Chars Out
>>>                 Processor      98405    6710609     535543   50002650
>>>               Route cache 2288708113 1141208459          0          0
>>>                     Total 2288806518 1147919068     535543   50002650
>>> FastEthernet0/4
>>>            Switching path    Pkts In   Chars In   Pkts Out  Chars Out
>>>                 Processor      89343   11874108  396765671 2089412449
>>>               Route cache  543340008 1149008067          0          0
>>>                     Total  543429351 1160882175  396765671 2089412449
>>>
>>> ....
>>>
>>>
>>> "sh int switching" shows the same problem for all interfaces : The 
>>> Fast path has 0 entries for all
>>> protocols including IP.
>>>
>>> Regards,
>>> Tassos
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> 
> ----------------------------------------------------------------------
>  Jon Lewis                   |  I route
>  Senior Network Engineer     |  therefore you are
>  Atlantic Net                |
> _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
> 

-- 
***************************************
         Tassos Chatzithomaoglou
Network Design & Development Department
              FORTHnet S.A.
          <achatz at forthnet.gr>
***************************************