IP addressing on an Ethernet subinterface

Discussion in 'Cisco' started by WAState, Feb 11, 2005.

  1. WAState

    WAState Guest


    We use an 802.11b link to exchange traffic with a (somewhat) remote
    location. We do not manage the equipment on their end. On our end, F0/1
    on a 2621 is connected to a Cisco 1200; in other words, the radio has a
    dedicated FE port on the router.

    We route several separate 192.168 address blocks to them over this
    connection. F0/1 on the 2621 has a secondary address in each of the
    subnets. At the other end, each of the address blocks goes to a
    different department.


    We need to track bandwidth consumption by subnet (i.e. by department)
    and make it easy for non-tech people to examine. Our initial thought
    was to use something like MRTG (free, works well) and point it to MIB
    info. No problem... we'll just create a subinterface on F0/1 for each
    subnet instead of using the present secondary address scheme. This will
    yield a separate IDB for each subinterface, each with its own MIB
    traffic counters, and MRTG can then be pointed at each subinterface to
    give users a nice graph to show traffic for each subnet/department.

    Alas, this led directly to the IOS requirement that subinterfaces be
    used as part of a VLAN. We're not running VLAN's, and since we don't
    control what the other end buys nor how they configure it, we cannot
    "just set them up."

    So... we have a single FE interface on a 2621. It runs directly into a
    Aironet 1200, which links to a client on the other end. We route
    multiple subnets over this link, and we need to conveniently track
    bandwidth consumption by subnet. A classic job for MRTG, except that we
    can't figure out how to create virtual interfaces for each subnet that
    MRTG can then access via SNMP.

    All suggestions appreciated. Thanks!
    WAState, Feb 11, 2005
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  2. Guest

    Check out if the IOS version on your 2621 supports NetFlow accounting.

    Probably requires that CEF be enabled
    , Feb 11, 2005
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  3. WAState

    WAState Guest

    Yes, the router is running 12.0(7)XK1 and does support NetFlow. I've
    enabled that on one interface to get familiar with it. However, its
    output (sho ip cache flow) does not yield bytes per packet data. It
    shows the distribution of packet sizes (for all src and dest addresses
    taken in aggregate) and shows packet count per flow, but there's no way
    to accurately get from that data to "bandwidth used by IP address

    WAState, Feb 15, 2005
  4. Merv

    Merv Guest

    > Suggestions?

    try sh ip cache flow verbose - this should show avg bytes info
    Merv, Feb 15, 2005
  5. WAState

    WAState Guest

    Yes, but as I said in my previous response that gives me (number of
    packets) and (average packet size). I can multiply the two values, but
    the result is not precise. I suppose I can live with that if that's as
    good as it gets, but the router has the detailed data so why not report

    Also: Do you know of a shareware NetFlow analyzer that runs on Windows?

    WAState, Feb 16, 2005
  6. Merv

    Merv Guest

    Merv, Feb 16, 2005
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