2811 high CPU and low throughput

[FabienneC]

Hello,

I am facing a problem on a 2811 router. The CPU is remaining around 60% and the router throughput is reaching at most 18 MB while according to the data sheet the 2811 maximum throughput is 61MB. I have checked the output interpreter in order to try and figure out the cause of the high CPU and to determine if it is affecting throughput but there are not processes consuming more than 10%.

I have attached the show tech-support and the show process cpu history outputs.

I appreciate your advise on the matter.

Thank you in advance,

Fabienne.

[Leo Laohoo]

The CPU is remaining around 60% and the router throughput is reaching at most 18 MB while according to the data sheet the 2811 maximum throughput is 61MB.

61 mbps is expressed in HALF duplex and un-encrypted traffic.

If you want the value of full duplex and encrypted traffic then you divide the value by 4 (which is 15.5).

[FabienneC]

Thank you, but does this apply for full duplex unencrypted traffic as well? because traffic on this router is not encrypted, the router is used as a voice gateway. But interfaces are running in full duplex speed.

[Leo Laohoo]

For full duplex and un-encrypted traffic then you cut the value in half.

Anyway ... 231/255 txload means the router is pushing as hard as it can.

FastEthernet0/0 is up, line protocol is up 
  Hardware is MV96340 Ethernet, address is 0017.5926.8678 (bia 0017.5926.8678)
  MTU 1500 bytes, BW 10000 Kbit/sec, DLY 100 usec, 
  reliability 255/255, txload 231/255, rxload 92/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  1., loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, 100BaseTX/FX
  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 never
  Input queue: 3/75/52/0 (size/max/drops/flushes); Total output drops: 4
  Queueing strategy: Class-based queueing
  Output queue: 0/1000/0 (size/max total/drops)
  30 second input rate 3636000 bits/sec, 2158 packets/sec
  30 second output rate 9068000 bits/sec, 2437 packets/sec
  164500107 packets input, 3504025871 bytes
  Received 451193 broadcasts, 0 runts, 0 giants, 1 throttles
  1688 input errors, 0 CRC, 0 frame, 0 overrun, 1688 ignored
  0 watchdog
  0 input packets with dribble condition detected
  178089966 packets output, 3313225908 bytes, 0 underruns
  0 output errors, 0 collisions, 2 interface resets
  15892 unknown protocol drops
  0 babbles, 0 late collision, 0 deferred
  0 lost carrier, 0 no carrier
  0 output buffer failures, 0 output buffers swapped out

Hmmmm ... Do you have CEF enabled?

[FabienneC]

Thank you

[Leo Laohoo]

Do you have CEF enabled?

[FabienneC]

yes ip cef is enabled, but the interrupt CPU percentage is high

[Leo Laohoo]

My opinion is that your router is being overwhelmed by the switch connected to Fast 0/0/  231/255 means it's >90%.

[FabienneC]

One more thing, even though the CPU over an hour is always around 60% the average over the last 72 hours in normal, so could this just be a temporary traffic load?

[Leo Laohoo]

so could this just be a temporary traffic load?

Depends on the link utilization of Fast 0/0.

[nkarpysh]

Hi Fabienne,

When you see utilization high on Fa0/0 you can check traffic there with followign commands - it will show you the packets sitting in the buffer. Then based on the MAc and ips in it you can see why those are sent to CPU and if it is possible to limit/eliminate those:

show buffer input-interface fa0/0 packet (or other keywords instead of packet).

Sorry don't have a chance to test this command but I hope shoudl work. Other veriant is to set up SPAN and sniffer that port as it seems to be most suspected for interrupts.

Nik

[FabienneC]

Thanks Nik.