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CISCO ROUTER 3845 CONSTANTLY SHOWS DISCARD PAQUETS AT WAN INTERFACE

Unanswered Question
Aug 28th, 2014
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Dear Sirs.

 

We have an 3845 cisco router which constantly shows discard paquets at wan interface.

there is not: saturation, CRC´s and any other anomalies at wan interface.

The IOS of the router is:

"flash:c3845-adventerprisek9-mz.151-3.T4.bin"

and the configuration of the wan interface is:

!
interface GigabitEthernet0/0
 description WAN|La Molina-IBM|CD=56619|IPVPN
 bandwidth 61440
 ip address 10.160.1.18 255.255.255.252
 ip accounting output-packets
 ip flow ingress
 ip flow egress
 ip nat inside
 ip virtual-reassembly in
 ip route-cache policy
 load-interval 30
 duplex full
 speed 100
 media-type rj45
 max-reserved-bandwidth 100
 service-policy output IPVPN
!

The error counters is:

SITEL-CD56619_IBM#sh int gigabitEthernet 0/0
GigabitEthernet0/0 is up, line protocol is up
  Hardware is BCM1125 Internal MAC, address is 001b.5358.2940 (bia 001b.5358.294
0)
  Description: WAN|La Molina-IBM|CD=56619|IPVPN
  Internet address is 10.160.1.18/30
  MTU 1500 bytes, BW 61440 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 86/255, rxload 35/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full Duplex, 100Mbps, media type is RJ45
  output flow-control is XON, input flow-control is XON
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, output hang never
  Last clearing of "show interface" counters 11w3d
  Input queue: 1/75/0/0 (size/max/drops/flushes); Total output drops: 2625448
  Queueing strategy: Class-based queueing
  Output queue: 0/1000/0 (size/max total/drops)
  30 second input rate 8469000 bits/sec, 3567 packets/sec
  30 second output rate 20822000 bits/sec, 4135 packets/sec
     4107004053 packets input, 3102483731 bytes, 0 no buffer
     Received 349220 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     4986 input errors, 0 CRC, 0 frame, 4986 overrun, 0 ignored
     0 watchdog, 4025131 multicast, 0 pause input
     3920684559 packets output, 3770059387 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     230444 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out
SITEL-CD56619_IBM#

 

Would you be mind telling us if we need to change the IOS due possible bugs or maybe failure at wan interface?

 

Thanks allot.

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ROGER FERNANDO ... Tue, 12/09/2014 - 10:03
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Dear Tagir.

 

We have changed the patch cord but the level of dropped paquet increments.

In the meanwhile we have arranged to change the model of router for the first quarter of 2015.

thank allot for your support.

 

Attn.

 

Roger

Joseph W. Doherty Thu, 08/28/2014 - 11:07
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Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

You don't need to saturate a link to encounter drops.

What's your service-policy look like and what are its stats?

ROGER FERNANDO ... Thu, 08/28/2014 - 11:41
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Hi Joseph.

 

the police are:

 

!
class-map match-any VOZ
 match access-group 100
class-map match-any DATOS
 match access-group 101
class-map match-any ROUTING
 description Reserva TRAFFIC BGP
 match ip precedence 6  7
 match mpls experimental topmost 6  7
 match access-group 111
class-map match-any Best_efford
 match any
!
!
policy-map IPVPN
 class ROUTING
  bandwidth 2048
 class VOZ
  priority 1024
  set ip precedence 5
 class class-default
  set ip precedence 1
  fair-queue 1024
!

SITEL-CD56619_IBM#sh policy-map interface gigabitEthernet 0/0
 GigabitEthernet0/0

  Service-policy output: IPVPN

    queue stats for all priority classes:

      queue limit 64 packets
      (queue depth/total drops/no-buffer drops) 0/0/0
      (pkts output/bytes output) 3201424/702931906

    Class-map: ROUTING (match-any)
      76696815 packets, 5312462084 bytes
      30 second offered rate 10000 bps, drop rate 0 bps
      Match: ip precedence 6  7
        76696777 packets, 5312460032 bytes
        30 second rate 10000 bps
      Match: mpls experimental topmost 6  7
        0 packets, 0 bytes
        30 second rate 0 bps
      Match: access-group 111
        38 packets, 2052 bytes
        30 second rate 0 bps
      Queueing
      queue limit 64 packets
      (queue depth/total drops/no-buffer drops) 0/0/0
      (pkts output/bytes output) 76696752/5407088943
      bandwidth 2048 kbps

    Class-map: VOZ (match-any)
      3201459 packets, 702979930 bytes
      30 second offered rate 1000 bps, drop rate 0 bps
      Match: access-group 100
        3201459 packets, 702979930 bytes
        30 second rate 1000 bps
      Priority: 1024 kbps, burst bytes 25600, b/w exceed drops: 35

      QoS Set
        precedence 5
          Packets marked 3201459

    Class-map: class-default (match-any)
      16487541763 packets, 7549715146267 bytes
      30 second offered rate 7430000 bps, drop rate 0 bps
      Match: any
      Queueing
      queue limit 64 packets
      (queue depth/total drops/no-buffer drops/flowdrops) 0/2638133/0/2638133
      (pkts output/bytes output) 3875117901/7947194068295
      QoS Set
        precedence 1
          Packets marked 16486715068
      Fair-queue: per-flow queue limit 16
SITEL-CD56619_IBM#
SITEL-CD56619_IBM#

 

the service policy is applied at giga interface.0/0

Our provider TELEFONICA have configured the policies and have configured as best-efford the police for DATA.

At GRUPO ROMERO, all router has police: GOLDEN for VOICE (voz) and SILVER for DATA.

But for this router, they used best efford to overcome the discarded paquets which I think is wrong.

 

waiting your sooner answer.,

 

Attn.

 

Joseph W. Doherty Fri, 08/29/2014 - 09:21
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Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Hmm, your class-default only has a queue-limit of 64 packets, and per flow queue limit of 16 packets.   Stats show as flowdrops.  This is likely much too shallow for a 100 Mbps port.

ROGER FERNANDO ... Fri, 08/29/2014 - 11:40
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Hi Joseph.

 

i appreciate your comments, but what can we do about it?

 

what is the best value for the queues and if we change them this will cause´ link down?

 

Attn.

Joseph W. Doherty Sun, 08/31/2014 - 04:30
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Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

What can you do about it?  Adjust queue-limit (if supported).

What's best values for queues?  That's an "it depends".  For a single TCP flow to be able to support path maximum bandwidth, buffers (queue-limit) needs to support BDP.

Will changing queue values take link down?  Normally, no, but you might impact a some "inflight" packets.

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