[nsp] High CPU & NAT

Stephen J. Wilcox steve at telecomplete.co.uk
Thu May 8 19:19:54 EDT 2003


You give the CPU as 68%/26%

The first % is interupts which is fast switching.. seems your high cpu is simply
load of switched traffic... but your stats below are a bit wierd, I dont know
the way they handle nat (so I'm not really answering yuor question properly!)
but why would it only be in one direction .. the nat is two way !

It would be interesting to know what 'sh ip int' looks like for these..

Steve

On Thu, 8 May 2003, Voralt wrote:

> Does anybody know if NAT is process-switched, or fast-switched on a 3640
> running 12.2(12)?  I have a customer with a 3640 with 2FE and 1 T1.  The
> total traffic through it is about 3Mbps, so it can easily handle it.
> However, they have a bunch of NAT's setup on it.
> 
> cisco-gw#sh ip nat stat
> Total active translations: 8271 (184 static, 8087 dynamic; 8039 extended)
> 
> 
> 
> The CPU gradually increases over time and eventually hits 100% and causes
> tons of dropped traffic.  Right now, it's about 70% over 5 minutes and the
> only thing of significance in the proc table is ip input.
> 
> CPU utilization for five seconds: 68%/26%; one minute: 74%; five minutes:
> 73%
>   30   451407504 131621758       3429 35.45% 38.84% 37.84%   0 IP Input
> 
> 
> 
> It's a little hard to see from the formatting mess below, but virtually
> everything in F2/0 and out 3/0 (from nat inside to nat outside) is process
> switched.  So this leads me to believe NAT is process switched.  I thought
> it would have been fast switched by now, but I could be wrong.  Any ideas?
> 
> 
> show int switching:
> 
> FastEthernet2/0 to DMZ
>           Throttle count          0
>         Drops         RP   10003415         SP          0
>   SPD Flushes       Fast          0        SSE          0
>   SPD Aggress       Fast          0
>  SPD Priority     Inputs          0      Drops          0
> 
>      Protocol       Path    Pkts In   Chars In   Pkts Out  Chars Out
>         Other    Process          4       3212      72369    4342140
>             Cache misses          0
>                     Fast          0          0          0          0
>                Auton/SSE          0          0          0          0
>            IP    Process  353413678 2270865909   26180460 2804527244
>             Cache misses       3913
>                     Fast      15170    3647946  326348309 2892067068
>                Auton/SSE          0          0          0          0
>           ARP    Process      69034    4151912      63199    3791940
>             Cache misses          0
> 
> 
> FastEthernet3/0
>           Throttle count          0
>         Drops         RP      23591         SP          0
>   SPD Flushes       Fast          0        SSE          0
>   SPD Aggress       Fast          0
>  SPD Priority     Inputs     116528      Drops          0
> 
>      Protocol       Path    Pkts In   Chars In   Pkts Out  Chars Out
>         Other    Process          0          0      72371    4342260
>             Cache misses          0
>                     Fast          0          0          0          0
>                Auton/SSE          0          0          0          0
>            IP    Process   20621237 2133783481  341505610  687586530
>             Cache misses     263078
>                     Fast  321349725  495104553       7748    2771807
>                Auton/SSE          0          0          0          0
>           ARP    Process     237557   14253420         56       3360
>             Cache misses          0
>                     Fast          0          0          0          0
>                Auton/SSE          0          0          0          0
>           CDP    Process      12127    4680986      12072    3766464
>             Cache misses          0
>                     Fast          0          0          0          0
>                Auton/SSE          0          0          0          0
> 
>                     Fast          0          0          0          0
>                Auton/SSE          0          0          0          0
> 
> 
> 
> 
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