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what causes flushes?

 
 
larry.vaden@gmail.com
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Posts: n/a
 
      07-18-2007
This rural ISP is having problems described below; any help would be
appreciated.

Configuration:
cisco 7206VXR (NPE300) processor with 229376K/65536K bytes of memory
IOS (tm) 7200 Software (C7200-K4P-M), Version 12.0(32)S6, RELEASE
SOFTWARE (fc3)

she-gw#show process cpu | incl utilization
CPU utilization for five seconds: 68%/46%; one minute: 67%; five
minutes: 66%

Issue: poor Miranda (http://miranda.ctd.anl.gov:7123) results from
customer's viewpoint, including lower downstream rates than upstream
rates; typically 3% of packets dropped when unix host pings unix host
on another router interface.

1st question: should we be concerned about the number of flushes
below?

kind regards/ldv

Larry Vaden
Internet Texoma, Inc.

she-gw#show interface Serial3/0 | incl counter
Last clearing of "show interface" counters 01:00:09
she-gw#show interface | incl Input queue:
Input queue: 1/4096/0/51372 (size/max/drops/flushes); Total output
drops: 0
---FE0/0, 18 subnets (secondaries)
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
0
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
0
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
0
Input queue: 0/75/0/22 (size/max/drops/flushes); Total output drops:
0
Input queue: 0/4096/0/0 (size/max/drops/flushes); Total output
drops: 0
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
0
Input queue: 0/75/0/29 (size/max/drops/flushes); Total output drops:
85
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
0
Input queue: 0/75/0/2272 (size/max/drops/flushes); Total output
drops: 0
Input queue: 24/75/49/107221 (size/max/drops/flushes); Total output
drops: 0
---Serial3/0, upstream DS3
Input queue: 0/75/0/501 (size/max/drops/flushes); Total output
drops: 0
Input queue: 0/75/0/1778 (size/max/drops/flushes); Total output
drops: 0
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
0
she-gw

 
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Gabriele Beltrame
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Posts: n/a
 
      07-18-2007

<(E-Mail Removed)> ha scritto nel messaggio
news:(E-Mail Removed) ups.com...
> This rural ISP is having problems described below; any help would be
> appreciated.
>
> Configuration:
> cisco 7206VXR (NPE300) processor with 229376K/65536K bytes of memory
> IOS (tm) 7200 Software (C7200-K4P-M), Version 12.0(32)S6, RELEASE
> SOFTWARE (fc3)
>
> she-gw#show process cpu | incl utilization
> CPU utilization for five seconds: 68%/46%; one minute: 67%; five
> minutes: 66%
>
> Issue: poor Miranda (http://miranda.ctd.anl.gov:7123) results from
> customer's viewpoint, including lower downstream rates than upstream
> rates; typically 3% of packets dropped when unix host pings unix host
> on another router interface.
>
> 1st question: should we be concerned about the number of flushes
> below?
>
> kind regards/ldv
>
> Larry Vaden
> Internet Texoma, Inc.
>
> she-gw#show interface Serial3/0 | incl counter
> Last clearing of "show interface" counters 01:00:09
> she-gw#show interface | incl Input queue:
> Input queue: 1/4096/0/51372 (size/max/drops/flushes); Total output
> drops: 0
> ---FE0/0, 18 subnets (secondaries)
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
> 0
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
> 0
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
> 0
> Input queue: 0/75/0/22 (size/max/drops/flushes); Total output drops:
> 0
> Input queue: 0/4096/0/0 (size/max/drops/flushes); Total output
> drops: 0
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
> 0
> Input queue: 0/75/0/29 (size/max/drops/flushes); Total output drops:
> 85
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
> 0
> Input queue: 0/75/0/2272 (size/max/drops/flushes); Total output
> drops: 0
> Input queue: 24/75/49/107221 (size/max/drops/flushes); Total output
> drops: 0
> ---Serial3/0, upstream DS3
> Input queue: 0/75/0/501 (size/max/drops/flushes); Total output
> drops: 0
> Input queue: 0/75/0/1778 (size/max/drops/flushes); Total output
> drops: 0
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
> 0
> she-gw
>


Hi,

Flushes generally occur when there is an excessive packet processing for
your Route Processor. Some "user" packets are to be discarded to let
priority packets be processed (e.g. control packets ( keepalives, routing
protocols traffic, other management traffic).
Sometimes a consistent number of flushed data is associated with some kind
of DoS attack.

Note that this protection come in place only with Process Switching; with
CEF enabled only a small percentage of traffic should be punted to the RP.

a) Assess why so many packets are process switched
b) Try and increase your input queue
c) Upgrade your route processor

Regards,
Gabriele


 
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vamsiguturu vamsiguturu is offline
Junior Member
Join Date: May 2009
Posts: 1
 
      05-28-2009
Hi

Am using Cisco Aironet 1240AG AP.
I tried to change the input queue size from default(75) to lower size(5).
I can see the size getting updated when I issue
--"show interface <my interface> 0".

But when my TCP Download is going on, when I issue the above command, I never seen the size or drop or flushes getting updated. I always see it as follows :: (0/5/0/0/).
 
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