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This Question is Not Answered 1 Correct Answer available (4 pts) 2 Helpful Answers available (2 pts)
12008 Views 12 Replies Latest reply: Sep 16, 2011 5:19 PM by IOScertsGoneMad RSS

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TxLoad and RxLoad

Sep 12, 2011 8:44 AM

Steven Williams 3,266 posts since
Jan 26, 2009

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

 

When I do a "show int vlan 1" and I see this output, what is the 255 based on? I have been in different conversations that say vlan's dont have bandwidth per say so what is the /255 based on?

  • Currently Being Moderated
    1. Sep 12, 2011 12:57 PM (in response to Steven Williams)
    Re: TxLoad and RxLoad

    Arbitrary number based on a percentage of the link.  I've never really paid any attention to those on the VLAN level unless the device is experiencing a performance issue.

     

    255/255 is 100% utilization of a link, but most of the time even if you have full utilization you'll see a reported value of something like 248+/255.  I cannot remember if I have ever seen 255/255.

     

    It's just a percentage, fwiw.

  • Brian 2,968 posts since
    Aug 17, 2009
    Currently Being Moderated
    3. Sep 13, 2011 11:03 PM (in response to Steven Williams)
    Re: TxLoad and RxLoad

    The reliability of an interface is always reported as a fraction of 255 (255/255 is 100% reliability), calculated as an exponential average over 5 minutes.  So you want to see the reliability at 255/255.  If this drops below this value, then you have problems on the link.  Typically, any layer 1 or layer 2 issues will bring this number down say 228/255.

     

    The load on an interface is also a fraction of 255 (255/255 is completely saturated), and is also calculated as an exponential average over 5 minutes.   You do NOT want to see the TX load or RX load at 255/255 or 100%, as this indicates a saturated link.  The configured bandwidth on the interface and the actual bandwidth utilized affect this number.  For example, you have a 100Mbps link and it is 50% utilized, you should see something like 128/255.

     

    Brian

     

    Message was edited by: Brian

  • bitlock76 17 posts since
    Mar 11, 2010
    Currently Being Moderated
    6. Sep 14, 2011 8:03 AM (in response to Steven Williams)
    Re: TxLoad and RxLoad

    I could be wrong, but wouldn't the "traffic used on a VLAN" be the aggregate of traffic load across all ports assigned to the VLAN?  The Vlan1 interface is just a virtual interface, not an actual load-bearing interface.  

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    7. Sep 14, 2011 11:11 AM (in response to Steven Williams)
    Re: TxLoad and RxLoad

    Why are you tracking the utilization of a VLAN??  That is my question.  Track the bottlenecks - which are the physical links.  Then track the CPU utilization to monitor overall box health.

  • Brian 2,968 posts since
    Aug 17, 2009
    Currently Being Moderated
    9. Sep 16, 2011 12:41 PM (in response to Steven Williams)
    Re: TxLoad and RxLoad

    Did you issue this command under the interface?  If so, why?  Below is the output from one of my distribution switches, notice there is no bandwidth configured under the interface.  However, in the output of the "sh interface" command, you see a bandwidth of 100,000 kbps or 100 Mbps.

     

    interface Vlan11
    ip address 192.168.11.1 255.255.255.0
    !

     

    DSW-1#sh int vlan 11
    Vlan11 is up, line protocol is up
      Hardware is CPU Interface, address is 0000.0c95.4c48 (bia 0000.0c95.4c48)
      Internet address is 192.168.11.1/24
      MTU 1500 bytes, BW 100000 Kbit, DLY 1000000 usec,
         reliability 255/255, txload 1/255, rxload 1/255

     

    I would say this is just a default bandwidth assigned to the interface just as what you get when you create a loopback interface.  Notice the "delay" on the interface as well.  Again, these are just defaults added by the IOS for such interfaces as loopbacks, tunnels, SVI, DVI, etc.  Remember what the bandwidth command is used for?   QoS and routing protocols.

     

    Brian

  • Currently Being Moderated
    10. Sep 16, 2011 12:52 PM (in response to Steven Williams)
    Re: TxLoad and RxLoad

    Again - why are you trying to measure a virtual entity?  Measure the links that feed VLAN1, you'll more likely run into a bottleneck there first.

  • Brian 2,968 posts since
    Aug 17, 2009
    Currently Being Moderated
    11. Sep 16, 2011 1:20 PM (in response to tnewshott)
    Re: TxLoad and RxLoad

    I agree with Travis here.  Since you mention you have many users coming in on VLAN1 and your servers are connected on this VLAN as well, try setting up Orion to monitor the "servers" ports.  These are the ports that are going to get overloaded as many users try to access them.  As the traffic load on a single server interface gets above 60% (continuous utilization) then upgrade to an Etherchannel (if 100Mb links) or 1Gb links (configure Etherchannel once utilization goes above 60%) then upgrade to 10Gb links for the servers.

     

    Brian

  •  IOScertsGoneMad  105 posts since
    Apr 30, 2010
    Currently Being Moderated
    12. Sep 16, 2011 5:19 PM (in response to Steven Williams)
    Re: TxLoad and RxLoad

    Make sure CEF is enabled if you ar running any sorta recent ios. 'ip cef' must be globally enabled for netflow to be working. just my 2 cents worth of b/w here!

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