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Interface Bandwidth Utilization calculation method

Jan 23, 2012 2:09 AM

Parveen 37 posts since
Apr 30, 2010

HI team,

 

i just want to know how i check interface over utilization and also wants to check how much a BW is utilizing in my network for this i don't wana use any monitoring tool suppose when i run command

 

SHOW INTERFACE F0/0 and check 5 min input and output rate is

 

5 minute input rate 72000 bits/sec, 37 packets/sec

5 minute output rate 334000 bits/sec, 41 packets/sec

 

so how can we calculate from above output that is it over utlizing or it is normal.pls clear it to me with example and formula use to calculate the utilization

  • Chad Spears CCNP CCDA CCNAS 751 posts since
    Jul 27, 2009
    Currently Being Moderated
    1. Jan 23, 2012 3:06 AM (in response to Parveen)
    Re: Interface Bandwidth Utilization calculation method

    Parveen-

     

    First I would suggest setting the load-interval to 30 seconds, this will give you a better representation of the bandwidth at the times you are issuing the command.  Can you set the load interval by issuing the "load-internal 30" interface command.

     

    Below you will see how we can use the show interface command to determine bandwidth utilization:

     

    WRMC-MC-RT-100-1#show int fa0/0

    FastEthernet0/0 is up, line protocol is up

      Description: LINK TO CHARTER | METRO-E TO CHS

      MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,

         reliability 255/255, txload 1/255, rxload 1/255

      30 second input rate 0 bits/sec, 1 packets/sec

      30 second output rate 1000 bits/sec, 1 packets/sec

         145488249 packets input, 1891788591 bytes

         Received 457 broadcasts, 0 runts, 0 giants, 48 throttles

         48 input errors, 0 CRC, 0 frame, 0 overrun, 48 ignored

         0 watchdog

         0 input packets with dribble condition detected

         143822386 packets output, 860392112 bytes, 0 underruns

     

    As you can see on my 100mbit interface I am currently using 1kbit/sec output and 0kbit/sec input on an average over the last 30 seconds.  This is almost no traffic.... (which it is early morning here, so no one in the office yet )

     

    However, you can use this command to monitor the bandwidth.  Some things to remember are:  If you are monitoring a "leased line" you may want to set the interface bandwidth using the "bandwidth" interface command.  Remember routing protocols will use the bandwidth to calculate the best path.  By setting the bandwidth to the accurate interface bandwidth it will help you monitor closer.

     

    Also, note the txload and rxload output.  This is a representation of the the interface utilization based on the bandwidth, input rate, and output rate calculations.

     

    HTH,
    CS

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  • cadetalain 2,728 posts since
    Sep 18, 2008
    Currently Being Moderated
    3. Jan 23, 2012 3:35 AM (in response to Parveen)
    Re: Interface Bandwidth Utilization calculation method

    Hi,

     

    on a Fastethernet interface having 72 kbs and 334 kbs is not overutilization, don't forget that the bandwidth command is only used by some routing protocols( EIGRP,OSPF) and by QoS tools like CBWFQ or LLQ,.

    To see the overutilization you should consider the physical speed of the interface which is 100Mbs here and compare the outputs you showed us but with a lower load-interval and also look at the packet drops on the interface

     

    Regards.

     

    Alain

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  • Chad Spears CCNP CCDA CCNAS 751 posts since
    Jul 27, 2009
    Currently Being Moderated
    4. Jan 23, 2012 3:37 AM (in response to Parveen)
    Re: Interface Bandwidth Utilization calculation method

    Parveen-

     

    Notice my output is in 30 second intervals, not 5 mins.  This will allow you to calculate the interface utlization easier.  Can you post your entire show interface output?

     

    Just looking at the output... it doesnt appear you are over utilizing.  It appears that your ouput rate is actually around 1kbit/sec.

     

    HTH,

    CS

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  • Brian 2,971 posts since
    Aug 17, 2009

    Keep in mind setting a lower interval will give you input and output statistics that are based on more instantaneous data.  Meaning it is more reactive to short bursts of traffic.  Not a good representation of the overall load on an interface.  Why?  Because when you set the interval low (30 seconds) as suggested, it is more reactive to small bursts of traffic, from say routing protocol updates or web page down loads.  When determining if the load on your interface is over utilized, you want to use a high interval (5 minute avg).  You then would take several outputs of the "sh interface" and if your 5 min avg are consistently above 70% then your link is over utilized.  You want to make sure the load on any interface does not exceed more then 70% for long periods of time.  Short bursts are acceptable and normal.  Long periods with consistently high averages are not.

     

    Hope this helps.

     

    Brian

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  • Brian 2,971 posts since
    Aug 17, 2009
    Currently Being Moderated
    7. Jan 23, 2012 4:47 AM (in response to Parveen)
    Re: Interface Bandwidth Utilization calculation method

    A BW of 256KB is 2Mbps (Bytes x 8 = bits).  Is the FE port the connection to your WAN?  Or do you have a serial port configured for say 256kbps?

     

    Based on your Tx and Rx load, no you are not over utilized.

     

    FastEthernet0/0 is up, line protocol is up

      Hardware is Gt96k FE, address is 001d.e60b.0a26 (bia 001d.

        Internet address is 192.168.8.1/24

      MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

         reliability 255/255, txload 1/255, rxload 1/255

     

    Brian

     

    Message was edited by: Brian

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  • arteq 1,766 posts since
    Sep 11, 2011
    Currently Being Moderated
    8. Jan 23, 2012 4:13 AM (in response to Brian)
    Re: Interface Bandwidth Utilization calculation method

    great info...

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  • Brian 2,971 posts since
    Aug 17, 2009
    Currently Being Moderated
    10. Jan 23, 2012 4:48 AM (in response to Parveen)
    Re: Interface Bandwidth Utilization calculation method

    That should be 256KB.  Typo on my part, sorry.  If you are connected to the WAN with a FE how is your BW only 256kb?  Please describe your setup a bit more.

     

    Brian

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  • Brian 2,971 posts since
    Aug 17, 2009
    Currently Being Moderated
    12. Jan 23, 2012 4:59 AM (in response to Parveen)
    Re: Interface Bandwidth Utilization calculation method

    The formula used to determine the utilization across any network connection is as follows:

     

    Utilization (U) Percentage = (Throughput/Data Rate) x 100

     

    Brian

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  • Brian 2,971 posts since
    Aug 17, 2009
    Currently Being Moderated
    14. Jan 23, 2012 5:10 AM (in response to Parveen)
    Re: Interface Bandwidth Utilization calculation method

    So do you have a serial port in the router?   Do you have a rate limit on the Fastethernet port?  Just trying to understand, because based on the output of your "show interface f0/0" command you are far from being over utilized.

     

    It is very simple.  Look at the out of your "show interface f0/0" command.

     

    FastEthernet0/0 is up, line protocol is up

      Hardware is Gt96k FE, address is 001d.e60b.0a26 (bia 001d.

        Internet address is 192.168.8.1/24

      MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

         reliability 255/255, txload 1/255, rxload 1/255

      Encapsulation ARPA, loopback not set

      Keepalive set (10 sec)

      Full-duplex, 100Mb/s, 100BaseTX/FX

      ARP type: ARPA, ARP Timeout 04:00:00

      Last input 00:00:01, output 00:00:00, output hang never

      Last clearing of "show interface" counters 05:57:38

      Input queue: 0/75/0/0 (size/max/drops/flushes); Total outp

      Queueing strategy: fifo

      Output queue: 0/40 (size/max)

      5 minute input rate 529000 bits/sec, 35 packets/sec

      5 minute output rate 742000 bits/sec,40 packets/sec

         568283 packets input, 165463931 bytes

         Received 3970 broadcasts, 0 runts, 0 giants, 0 throttle

         0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

         0 watchdog

         0 input packets with dribble condition detected

         596783 packets output, 453850117 bytes, 0 underruns

         0 output errors, 0 collisions, 0 interface resets

         0 babbles, 0 late collision, 0 deferred

         0 lost carrier, 0 no carrier

         0 output buffer failures, 0 output buffers swapped out

     

    Do you see the values in RED?  When you see the following 225/255 or 240/255 etc then your load is going up.  A load of 255/255 is completely saturated.  Not good.  So, you want to see low numbers here.  The lower the better.  When these are high, then look at the numbers in BLUE.  Use the formula from my previous post and calculate the Utilization Percentage.

     

    Brian

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