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Should CEF be enabled?

Posted on 2011-10-05
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Last Modified: 2012-05-12
It seems that my switch is process switching all packets.

Is that a bad thing?

sh cef state
CEF Status:
 RP instance
 common CEF disabled
IPv4 CEF Status:
 CEF disabled/not running
 dCEF disabled/not running
 CEF switching disabled/not running
 universal per-destination load sharing algorithm, id 83852352
IPv6 CEF Status:
 CEF disabled/not running
 dCEF disabled/not running
 universal per-destination load sharing algorithm, id 83852352

sh int fa1/0/1 stats
FastEthernet1/0/1
          Switching path    Pkts In   Chars In   Pkts Out  Chars Out
               Processor          0          0   11260657  720682048
             Route cache          0          0          0          0
                   Total          0          0   11260657  720682048



sh int gi1/0/1 stats
GigabitEthernet1/0/1
          Switching path    Pkts In   Chars In   Pkts Out  Chars Out
               Processor          0          0  294692675 18865399070
             Route cache          0          0          0          0
                   Total          0          0  294692675 18865399070

sh proc cpu history
    9939574447146829372248352929273236232793733384339294722173347392635273
    9209498176942196885333762109858704126390703929105596739950164994544489
100 *  *           *           *          *         * *           *
 90 ** *           *         * *          *         * *           *
 80 ** * *   *   * * *   *   * * *        * *   *   * * *   *     *     *
 70 ** * *   *   * * *   *   * * *       ** *   *   * * *   *   * * *   *
 60 ** * *   *  ** * *   * * * * *   *   ** *   *   * * *   *   * * *   *
 50 ** **** **  ** * *   * * * * *   *   ** *   **  * ***   *  ** * * * *
 40 ** ******* *** ***  **** * * **  *   ** *  ***  * ***   *  **** * * **
 30 ********** ******** **** * ******* ****************** * ******* *** **
 20 **********************************************************************
 10 ######################################################################
   0....5....1....1....2....2....3....3....4....4....5....5....6....6....7.
             0    5    0    5    0    5    0    5    0    5    0    5    0
                   CPU% per hour (last 72 hours)
                  * = maximum CPU%   # = average CPU%
0
Comment
Question by:Dragon0x40
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18 Comments
 
LVL 26

Accepted Solution

by:
Soulja earned 600 total points
ID: 36919235
Yes, enable CEF.
0
 
LVL 22

Expert Comment

by:eeRoot
ID: 36919284
What kind of switch is this and what network devices do it connect to?  
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LVL 28

Assisted Solution

by:mikebernhardt
mikebernhardt earned 200 total points
ID: 36919363
+1 on enabling CEF
0
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Author Comment

by:Dragon0x40
ID: 36919379
On a 3750 should I run "ip cef distributed" as I don't see a <cr> after "ip cef ?"

right now my processes show

 sh proc cpu
CPU utilization for five seconds: 9%/2%; one minute: 7%; five minutes: 7%

Does this mean that 2% of my cpu is being used for process switching?

0
 
LVL 26

Expert Comment

by:Soulja
ID: 36919476
IP Cef should be it.
0
 

Author Comment

by:Dragon0x40
ID: 36919781
WS-C3750-48TS-S

#ip cef ?
  distributed         Distributed Cisco Express Forwarding
  linecard            CEF linecard commands
  load-sharing        Load sharing
  optimize            Optimizations
  traffic-statistics  Enable collection of traffic statistics
0
 
LVL 26

Expert Comment

by:Soulja
ID: 36919905
Are you saying that is it not excepting just "IP CEF"? Have you tried just entering it. Just because <cr> is not listed doesn't mean it is not an option.
0
 
LVL 10

Expert Comment

by:ddiazp
ID: 36919916
ip cef distributed

is what you want
0
 
LVL 26

Expert Comment

by:Soulja
ID: 36919934
@ddiazp

Can you explain why?
0
 
LVL 10

Assisted Solution

by:ddiazp
ddiazp earned 1200 total points
ID: 36919968
"ip cef" was deprecated in favor of "ip cef distributed". They both have the same function. The rest of the commands are advanced features for optimizing and even monitoring (sla) that you're probably not looking

Can you do 'show int fa1/0/1' and 'show int gi1/0/1' and post how many packets per second these interfaces are processing?
0
 
LVL 10

Expert Comment

by:ddiazp
ID: 36920002
Also, in addition, to perform any further CEF/dCEF functions, you need to have CEF/dCEF running at least:

•Enabling CEF or dCEF (Required)
•Configuring Load Balancing for CEF (Optional)
•Configuring Network Accounting for CEF (Optional)
•Configuring Distributed Tunnel Switching for CEF (Optional)

more info: http://www.cisco.com/en/US/docs/ios/12_1/switch/configuration/guide/xcdcefc.html
0
 
LVL 26

Expert Comment

by:Soulja
ID: 36920074
@ddiazp

Thanks
0
 
LVL 26

Expert Comment

by:Soulja
ID: 36920080
My only question is stated above. Have the author tried entering ip cef? I still don't see that not being an available command.
0
 

Author Comment

by:Dragon0x40
ID: 36921583
I can't enter "ip cef" unless I get authorization.

I thought it would be easy just enter "ip cef distributed" and be done.

Wouldn't just that command help with not punting all packets to the CPU?
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LVL 10

Assisted Solution

by:ddiazp
ddiazp earned 1200 total points
ID: 36922228
you can just enter ip cef distributed and be done
0
 
LVL 15

Expert Comment

by:greg ward
ID: 36922524
can you paste the top 10 from this
 show processes cpu sorted 5min

Greg
0
 

Author Comment

by:Dragon0x40
ID: 36922554
I will post sh processes tomorrow.

If we really should have cef on all our access layer switches how do I convince the people I work with?
0
 

Author Comment

by:Dragon0x40
ID: 36934492
show processes cpu sorted 5min
CPU utilization for five seconds: 5%/0%; one minute: 6%; five minutes: 6%
 PID       Runtime(ms)   Invoked      uSecs   5Sec      1Min     5Min TTY Process
 212         66656092 277670662        240  0.15%  0.33%  0.34%   0 Spanning Tree
 150          61978233  30163250       2054  0.15%  0.18%  0.20%   0 HRPC qos request
 141          78542874 598514645        131  0.15%  0.18%  0.16%   0 Hulc LED Process
   4             30834452    3033192     10165  0.00%  0.15%  0.12%   0 Check heaps
 221                      443           173       2560  0.00%  0.26%  0.10%   1 SSH Process
 104           38443784  52361199         734  0.00%  0.11%  0.09%   0 hpm counter proc
 105           24869316 108972972        228  0.15%  0.09%  0.09%   0 HRPC pm-counters
  69             14395718  70120457        205   0.00%  0.02%  0.04%   0 hrpc <- response
 306                1340675    716662       1870  0.00%  0.01%  0.02%   0 SNMP ENGINE
  65              62802391344647164             4  0.00%  0.04%  0.01%   0 Fifo Error Detec
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