NAME

    SNMP::Info - Object Oriented Perl5 Interface to Network devices and MIBs
    through SNMP.

VERSION

    SNMP::Info - Version 0.8

AUTHOR

    Max Baker

    SNMP::Info was created at UCSC for the netdisco project
    (www.netdisco.org) and is now maintained by Max Baker.

SYNOPSIS

     use SNMP::Info;

     my $info = new SNMP::Info( 
                                # Auto Discover more specific Device Class
                                AutoSpecify => 1,
                                Debug       => 1,
                                # The rest is passed to SNMP::Session
                                DestHost    => 'router',
                                Community   => 'public',
                                Version     => 2 
                              ) or die "Can't connect to device.\n"

     my $err = $info->error();
     die "SNMP Community or Version probably wrong connecting to device. $err\n" if defined $err;

     $name  = $info->name();
     $class = $info->class()
     print "SNMP::Info is using this device class : $class\n";

     # Find out the Duplex status for the ports
     my $interfaces = $info->interfaces();
     my $i_duplex   = $info->i_duplex();

     # Get CDP Neighbor info
     my $c_if       = $info->c_if();
     my $c_ip       = $info->c_ip();
     my $c_port     = $info->c_port();

     # Print out data per port
     foreach my $iid (keys %$interfaces){
        my $duplex = $i_duplex->{$iid};
        # Print out physical port name, not snmp iid
        my $port  = $interfaces->{$iid};

        # The CDP Table has table entries different than the interface tables.
        # So we use c_if to get the map from cdp table to interface table.

        my %c_map = reverse %$c_if; 
        my $c_key = $c_map{$iid};
        my $neighbor_ip   = $c_ip->{$c_key};
        my $neighbor_port = $c_port->{$c_key};

        print "$port: $duplex duplex";
        print " connected to $neighbor_ip / $neighbor_port\n" if defined $remote_ip;
        print "\n";

     }

SUPPORT

    Please direct all support, help, and bug requests to the snmp-info-users
    Mailing List at
    <http://lists.sourceforge.net/lists/listinfo/snmp-info-users>

DESCRIPTION

    SNMP::Info gives an object oriented interface to information obtained
    through SNMP.

    This module lives at http://snmp-info.sourceforge.net Check for newest
    version and documentation.

    This module is geared towards network devices. Subclasses exist for a
    number of network devices and common MIBs.

    The idea behind this module is to give a common interface to data from
    network devices, leaving the device-specific hacks behind the scenes in
    subclasses.

    In the SYNOPSIS example we fetch the name of all the ports on the device
    and the duplex setting for that port with two methods -- interfaces()
    and i_duplex().

    The information may be coming from any number of MIB files and is very
    vendor specific. SNMP::Info provides you a common method for all
    supported devices.

    Adding support for your own device is easy, and takes little much SNMP
    knowledge.

    The module is not limited to network devices. Any MIB or device can be
    given an objected oriented front-end by making a module that consists of
    a couple hashes. See EXTENDING SNMP::INFO.

  Requirements

    1. Net-SNMP
        To use this module, you must have Net-SNMP installed on your system.
        More specifically you need the Perl modules that come with it.

        DO NOT INSTALL SNMP:: or Net::SNMP from CPAN!

        The SNMP module is matched to an install of net-snmp, and must be
        installed from the net-snmp source tree.

        The Perl module "SNMP" is found inside the net-snmp distribution. Go
        to the perl/ directory of the distribution to install it, or run
        "./configure --with-perl-modules" from the top directory of the
        net-snmp distribution.

        Net-SNMP can be found at http://net-snmp.sourceforge.net

        Version 5.0.2 or greater is recommended. Various version 4's will
        work, and 5.0.1 is kinda flaky on the Perl side.

        Note: Net-SNMP was previously called ucd-snmp.

    2. MIBS
        SNMP::Info operates on textual descriptors found in MIBs. MIBs are
        text databases that are freely and easily obtainable on the Net.

        Make sure that your snmp.conf is updated to point to your MIB
        directory and that the MIBs are world-readable.

        Then run "snmpconf" and setup that directory as default. Move
        snmp.conf into /usr/local/share/snmp when you are done.

        Basic MIBs
            A minimum amount of MIBs to have are the Version 2 MIBs from
            Cisco, found at

            ftp://ftp.cisco.com/pub/mibs/v2/v2.tar.gz

            To install them :

             mkdir -p /usr/local/share/snmp/mibs && cd /usr/local/share/snmp/mibs && tar xvfz /path/to/v2.tar.gz 

        Version 1 MIBs
            You will also need to install some of the version one MIBs from
            Cisco :

            ftp://ftp.cisco.com/pub/mibs/v1/v1.tar.gz

            Extract

            BRIDGE-MIB
            SNMP-REPEATER-MIB
            STAND-ALONE-ETHERNET-SWITCH-MIB (ESSWITCH-MIB)

            by running

             mkdir -p /usr/local/share/snmp/mibs
             cd /usr/local/share/snmp/mibs
             tar xvfz /path/to/v1.tar.gz BRIDGE-MIB.my SNMP-REPEATER-MIB.my ESSWITCH-MIB.my

        Fix CISCO-TC-MIB
            There is a problem with the Cisco file CISCO-TC.my which is
            included from lots of other MIBs. Make the following changes if
            you run into errors about "Unsigned32" in this file.

            Edit /usr/local/share/snmp/mibs/CISCO-TC.my

            Comment out line 192 that says "SMI Unsigned32" with two dashes.

                -- SMI Unsigned32

            Add "Unsigned32" to the imports after line 19:

                IMPORTS
                    MODULE-IDENTITY,
                    Gauge32,
                    Integer32,
                    Counter64,
                    Unsigned32,
                        FROM SNMPv2-SMI

        More Specific MIBs
            Some non-cisco subclasses will need MIBs other than the basic
            one available from Cisco.

            Check below under each subclass for requirements.

  Design Goals

    1. Use of textual MIB leaf identifier and enumerated values

        * All values are retrieved via MIB Leaf node names
            For example SNMP::Info has an entry in its %GLOBALS hash for
            ``sysName'' instead of 1.3.6.1.2.1.1.5.

        * Data returned is in the enumerated value form.
            For Example instead of looking up 1.3.6.1.2.1.2.2.1.3 and
            getting back 23

            SNMP::Info will ask for "RFC1213-MIB::ifType" and will get back
            "ppp".

    2. SNMP::Info is easily extended to new devices
        You can create a new subclass for a device by providing four hashes
        : %GLOBALS, %MIBS, %FUNCS, and %MUNGE.

        Or you can override any existing methods from a parent class by
        making a short subroutine.

        See the section EXTENDING SNMP::INFO for more details.

        When you make a new subclass for a device, please be sure to send it
        back to the developers at snmp@warped.org for inclusion in the next
        version.

  Subclasses

    These are the subclasses that implement MIBs and support devices:

    Required MIBs not included in the install instructions above are noted
    here.

   MIB Subclasses

    These subclasses implement method to access one or more MIBs. These are
    not used directly, but rather inherited from device subclasses.

    SNMP::Info::Bridge
        BRIDGE-MIB (RFC1286). Inherited by devices with Layer2 service.

    SNMP::Info::CDP
        CISCO-CDP-MIB. Cisco Discovery Protocol (CDP) Support. Inherited by
        devices serving Layer2 or Layer3.

    SNMP::Info::CiscoStats
        Provides common interfaces for memory, cpu, and os statistics for
        Cisco devices. Provides methods for information in :
        OLD-CISCO-CPU-MIB, CISCO-PROCESS-MIB and CISCO-MEMORY-POOL-MIB

    SNMP::Info::Entity
        ENTITY-MIB. Used for device info in Cisco and other vendors.

    SNMP::Info::EtherLike
        ETHERLIKE-MIB (RFC1398) - Some Layer3 devices implement this MIB, as
        well as some Aironet Layer 2 devices (non Cisco).

    SNMP::Info::MAU
        MAU-MIB (RFC2668). Some Layer2 devices use this for extended
        Ethernet (Media Access Unit) interface information.

   Device Subclasses

    These subclasses inherit from one or more classes to provide a common
    interface to data obtainable from network devices.

    SNMP::Info::Layer1
        Generic Layer1 Device subclass.

        SNMP::Info::Layer1::Allied
            Subclass for Allied Telesys Repeaters / Hubs.

            Requires ATI-MIB

            See SNMP::Info::Layer1::Allied for where to get MIBs required.

        SNMP::Info::Layer1::Asante
            Subclass for Asante 1012 Hubs.

            Requires ASANTE-HUB1012-MIB

            See SNMP::Info::Layer1::Asante for where to get MIBs required.

    SNMP::Info::Layer2
        Generic Layer2 Device subclass.

        SNMP::Info::Layer2::Bay
            Bay Networks BayStack switch Support. Provides translation from
            Bay Network Topology Table information to CDP.

            Requires SYNOPTICS-ROOT-MIB and S5-ETH-MULTISEG-TOPOLOGY-MIB

            See SNMP::Info::Bay for where to get MIBs required.

        SNMP::Info::Layer2::C1900
            Subclass for Cisco Catalyst 1900 and 1900c Devices running
            CatOS.

        SNMP::Info::Layer2::C2900
            Subclass for Cisco Catalyst 2900 and 3500XL devices running IOS.

        SNMP::Info::Layer2::Catalyst
            Subclass for Cisco Catalyst switches running CatOS. These
            switches usually report a model number that starts with ''wsc''.
            Note that this class does not support everything that has the
            name Catalyst.

        SNMP::Info::Layer2::HP
            Subclass for HP Procurve Swithces

            Requires HP-ICF-OID and ENTITY-MIB downloaded from HP.

            See SNMP::Info::Layer2::HP for more info.

    SNMP::Info::Layer3
        Generic Layer3 and Layer2+3 Device subclass.

        SNMP::Info::Layer3::Aironet
            Subclass for Cisco Aironet wireless access points (AP).

            MIBs for these devices now included in v2.tar.gz available from
            ftp.cisco.com.

        SNMP::Info::Layer3::Foundry
            No longer supported.

            Subclass for older Foundry Network devices.

            Requires FOUNDRY-SN-ROOT-MIB.

            See SNMP::Info::Layer3::Foundry for more info.

        SNMP::Info::Layer3::C3550
            Subclass for Cisco Catalyst 3550 2/3 switches running IOS.

  Thanks

    Thanks for testing and coding help (in no particular order) to : Andy
    Ford, Brian Wilson, Jean-Philippe Luiggi, Dána Watanabe

USAGE

  Constructor

    new()
        Creates a new object and connects via SNMP::Session.

         my $info = new SNMP::Info( 'Debug'       => 1,
                                    'AutoSpecify' => 1,
                                    'BigInt'      => 1
                                    'DestHost'    => 'myrouter',
                                    'Community'   => 'public',
                                    'Version'     => 2
                                  ) or die;

        SNMP::Info Specific Arguments :

         AutoSpecify = Returns an object of a more specific device class
                       *See specify() entry*
         Debug       = Prints Lots of debugging messages
         Session     = SNMP::Session object to use instead of connecting on own.
         BigInt      = Return Math::BigInt objects for 64 bit counters.  Sets on a global scope, not object.
         RetryNoSuch = When using SNMP Version 1, try reading values even if they come back
                       as "no such variable in this MIB".  Defaults to true, set to false if
                       so desired.  This feature lets you read SNMPv2 data from an SNMP version
                       1 connection, and should probably be left on.

        All other arguments are passed to SNMP::Session.

        See SNMP::Session for a list of other possible arguments.

        A Note about the wrong Community string or wrong SNMP Version :

        If a connection is using the wrong community string or the wrong
        SNMP version, the creation of the object will not fail. The device
        still answers the call on the SNMP port, but will not return
        information. Check the error() method after you create the device
        object to see if there was a problem in connecting.

        A note about SNMP Versions :

        Some older devices don't support SNMP version 2, and will not return
        anything when a connection under Version 2 is attempted.

        Some newer devices will support Version 1, but will not return all
        the data they might have if you had connected under Version 1

        When trying to get info from a new device, you may have to try
        version 2 and then fallback to version 1.

  Data is Cached

    Methods and subroutines requesting data from a device will only load the
    data once, and then return cached versions of that data.

    Run $info->load_METHOD() where method is something like 'i_name' to
    reload data from a table method.

    Run $info->clear_cache() to clear the cache to allow reload of both
    globals and table methods.

  Object Scalar Methods

    These are for package related data, not direcly supplied from SNMP.

    $info->clear_cache()
        Clears the cached data. This includes GLOBALS data and TABLE METHOD
        data.

    $info->debug(1)
        Returns current debug status, and optionally toggles debugging info
        for this object.

    $info->device_type()
        Returns the Subclass name for this device. "SNMP::Info" is returned
        if no more specific class is available.

        First the device is checked for Layer 3 support and a specific
        subclass, then Layer 2 support and subclasses are checked for.

        This means that Layer 2 / 3 switches and routers will fall under the
        SNMP::Info::Layer3 subclasses.

        If the device still can be connected to via SNMP::Info, then
        SNMP::Info is returned.

        Algorithm for Subclass Detection:

                Layer3 Support                     -> SNMP::Info::Layer3
                    Aironet (non IOS)              -> SNMP::Info::Layer3::Aironet
                    Catalyst 3550                  -> SNMP::Info::Layer3::C3550
                    Catalyst 6500                  -> SNMP::Info::Layer3::C6500
                    Foundry                        -> SNMP::Info::Layer3::Foundry
                Elsif Layer2 (no Layer3)           -> SNMP::Info::Layer2 
                    Aironet (Cisco) AP1100         -> SNMP::Info::Layer2::Aironet
                    Bay Networks                   -> SNMP::Info::Layer2::Bay
                    Catalyst 1900                  -> SNMP::Info::Layer2::C1900
                    Catalyst 2900XL/2950(IOS)      -> SNMP::Info::Layer2::C2900
                    Catalyst 3500XL (3548) IOS     -> SNMP::Info::Layer2::C2900
                    Catalyst 3550/3548             -> SNMP::Info::Layer3::C3550
                    Catalyst WS-C 2926,5xxx        -> SNMP::Info::Layer2::Catalyst
                    HP Procurve                    -> SNMP::Info::Layer2::HP
                Elsif Layer1 Support               -> SNMP::Info::Layer1
                    Allied                         -> SNMP::Info::Layer1::Allied
                    Asante                         -> SNMP::Info::Layer1::Asante
                Else                               -> SNMP::Info

    $info->error(no_clear)
        Returns Error message if there is an error, or undef if there is
        not.

        Reading the error will clear the error unless you set the no_clear
        flag.

    $info->has_layer(3)
        Returns non-zero if the device has the supplied layer in the OSI
        Model

        Returns "undef" if the device doesn't support the layers() call.

    $info->snmp_comm()
        Returns SNMP Community string used in conncetion

    $info->snmp_ver()
        Returns SNMP Version used for this connection

    $info->specify()
        Returns an object of a more-specific subclass.

         my $info = new SNMP::Info(...);
         # Returns more specific object type
         $info = $info->specific();

        Usually this method is called internally from new(AutoSpecify => 1)

        See device_type() entry for how a subclass is chosen.

  Globals (Scalar Methods)

    These are methods to return scalar data from RFC1213.

    Some subset of these is probably available for any network device that
    speaks SNMP.

    $info->uptime()
        Uptime in hundreths of seconds since device became available.

        (sysUpTime)

    $info->contact()
        (sysContact)

    $info->name()
        (sysName)

    $info->location()
        (sysLocation)

    $info->layers()
        This returns a binary encoded string where each digit represents a
        layer of the OSI model served by the device.

            eg: 01000010  means layers 2 (physical) and 7 (Application) 
                          are served.

        Note: This string is 8 digits long.

        See $info->has_layer()

        (sysServices)

    $info->ports()
        Number of interfaces available on this device.

        Not too useful as the number of SNMP interfaces usually does not
        correspond with the number of physical ports

        (ifNumber)

  Table Methods

    Each of these methods returns a hash_reference to a hash keyed on the
    interface index in SNMP.

    Example : $info->interfaces() might return

        { '1.12' => 'FastEthernet/0',
          '2.15' => 'FastEthernet/1',
          '9.99' => 'FastEthernet/2'
        }

    The key is what you would see if you were to do an snmpwalk, and in some
    cases changes between reboots of the network device.

  Partial Table Fetches

    If you want to get only a part of an SNMP table and you know the IID for
    the part of the table that you want, you can specify it in the call:

        $local_routes = $info->ipr_route('192.168.0');

    This will only fetch entries in the table that start with 192.168.0,
    which in this case are routes on the local network.

    Remember that you must supply the partial IID (a numeric OID).

    Partial table results are not cached.

   Interface Information

    $info->interfaces()
        This methods is overriden in each subclass to provide a mapping
        between the Interface Table Index (iid) and the physical port name.

    $info->if_ignore()
        Returns a reference to a hash where key values that exist are
        interfaces to ignore.

        Ignored interfaces are ones that are usually not physical ports or
        Virtual Lans (VLANs) such as the Loopback interface, or the CPU
        interface.

    $info->i_index()
        Default SNMP IID to Interface index.

        (ifIndex)

    $info->i_description()
        Description of the interface. Usually a little longer single word
        name that is both human and machine friendly. Not always.

        (ifDescr)

    $info->i_type()
        Interface type, such as Vlan, 10baseT, Ethernet, Serial

        (ifType)

    $info->i_mtu()
        INTEGER. Interface MTU value.

        (ifMtu)

    $info->i_speed()
        Speed of the link, human format. See munge_speed() later in document
        for details.

        (ifSpeed)

    $info->i_mac()
        MAC address of the interface. Note this is just the MAC of the port,
        not anything connected to it.

        (ifPhysAddress)

    $info->i_up()
        Link Status of the interface. Typical values are 'up' and 'down'.

        (ifOperStatus)

    $info->i_up_admin()
        Administrative status of the port. Typical values are 'enabled' and
        'disabled'.

        (ifAdminStatus)

    $info->i_name()
        Interface Name field. Supported by a smaller subset of devices, this
        fields is often human set.

        (ifName)

    $info->i_alias()
        Interface Name field. For certain devices this is a more human
        friendly form of i_description(). For others it is a human set field
        like i_name().

        (ifAlias)

   Interface Statistics

    $info->i_octet_in(), $info->i_octets_out(), $info->i_octet_in64(),
    $info->i_octets_out64()
        Bandwidth.

        Number of octets sent/received on the interface including framing
        characters.

        64 bit version may not exist on all devices.

        NOTE: To manipulate 64 bit counters you need to use Math::BigInt,
        since the values are too large for a normal Perl scalar. Set the
        global $SNMP::Info::BIGINT to 1 , or pass the BigInt value to new()
        if you want SNMP::Info to do it for you.

        (ifInOctets) (ifOutOctets) (ifHCInOctets) (ifHCOutOctets)

    $info->i_errors_in(), $info->i_errors_out()
        Number of packets that contained an error prventing delivery. See
        IF-MIB for more info.

        (ifInErrors) (ifOutErrors)

    $info->i_pkts_ucast_in(), $info->i_pkts_ucast_out(),
    $info->i_pkts_ucast_in64(), $info->i_pkts_ucast_out64()
        Number of packets not sent to a multicast or broadcast address.

        64 bit version may not exist on all devices.

        (ifInUcastPkts) (ifOutUcastPkts) (ifHCInUcastPkts)
        (ifHCOutUcastPkts)

    $info->i_pkts_nucast_in(), $info->i_pkts_nucast_out(),
        Number of packets sent to a multicast or broadcast address.

        These methods are depricated by i_pkts_multi_in() and
        i_pkts_bcast_in() according to IF-MIB. Actual device usage may vary.

        (ifInNUcastPkts) (ifOutNUcastPkts)

    $info->i_pkts_multi_in() $info->i_pkts_multi_out(),
    $info->i_pkts_multi_in64(), $info->i_pkts_multi_out64()
        Number of packets sent to a multicast address.

        64 bit version may not exist on all devices.

        (ifInMulticastPkts) (ifOutMulticastPkts) (ifHCInMulticastPkts)
        (ifHCOutMulticastPkts)

    $info->i_pkts_bcast_in() $info->i_pkts_bcast_out(),
    $info->i_pkts_bcast_in64() $info->i_pkts_bcast_out64()
        Number of packets sent to a broadcast address on an interface.

        64 bit version may not exist on all devices.

        (ifInBroadcastPkts) (ifOutBroadcastPkts) (ifHCInBroadcastPkts)
        (ifHCOutBroadcastPkts)

   IP Address Table

    Each entry in this table is an IP address in use on this device. Usually
    this is implemented in Layer3 Devices.

    $info->ip_index()
        Maps the IP Table to the IID

        (ipAdEntIfIndex)

    $info->ip_table()
        Maps the Table to the IP address

        (ipAdEntAddr)

    $info->ip_netmask()
        Gives netmask setting for IP table entry.

        (ipAdEntNetMask)

    $info->ip_broadcast()
        Gives broadcast address for IP table entry.

        (ipAdEntBcastAddr)

   IP Routing Table

    $info->ipr_route()
        The route in question. A value of 0.0.0.0 is the default gateway
        route.

        ("ipRouteDest")

    $info->ipr_if()
        The interface (IID) that the route is on. Use interfaces() to map.

        ("ipRouteIfIndex")

    $info->ipr_1()
        Primary routing metric for this route.

        ("ipRouteMetric1")

    $info->ipr_2()
        If metrics are not used, they should be set to -1

        ("ipRouteMetric2")

    $info->ipr_3()
        ("ipRouteMetric3")

    $info->ipr_4()
        ("ipRouteMetric4")

    $info->ipr_5()
        ("ipRouteMetric5")

    $info->ipr_dest()
        From RFC1213:

          "The IP address of the next hop of this route.
          (In the case of a route bound to an interface
          which is realized via a broadcast media, the value
          of this field is the agent's IP address on that
          interface.)"

        ("ipRouteNextHop")

    $info->ipr_type()
        From RFC1213:

            other(1),        -- none of the following
            invalid(2),      -- an invalidated route
                             -- route to directly
            direct(3),       -- connected (sub-)network
                             -- route to a non-local
            indirect(4)      -- host/network/sub-network

              "The type of route.  Note that the values
              direct(3) and indirect(4) refer to the notion of
              direct and indirect routing in the IP
              architecture.

              Setting this object to the value invalid(2) has
              the effect of invalidating the corresponding entry
              in the ipRouteTable object.  That is, it
              effectively disassociates the destination
              identified with said entry from the route
              identified with said entry.  It is an
              implementation-specific matter as to whether the
              agent removes an invalidated entry from the table.
              Accordingly, management stations must be prepared
              to receive tabular information from agents that
              corresponds to entries not currently in use.
              Proper interpretation of such entries requires
              examination of the relevant ipRouteType object."

        ("ipRouteType")

    $info->ipr_proto()
        From RFC1213:

            other(1),       -- none of the following
                            -- non-protocol information,
                            -- e.g., manually configured
            local(2),       -- entries
                            -- set via a network
            netmgmt(3),     -- management protocol
                            -- obtained via ICMP,
            icmp(4),        -- e.g., Redirect
                            -- the remaining values are
                            -- all gateway routing
                            -- protocols
            egp(5),
            ggp(6),
            hello(7),
            rip(8),
            is-is(9),
            es-is(10),
            ciscoIgrp(11),
            bbnSpfIgp(12),
            ospf(13),
            bgp(14)

        ("ipRouteProto")

    $info->ipr_age()
        Seconds since route was last updated or validated.

        ("ipRouteAge")

    $info->ipr_mask()
        Subnet Mask of route. 0.0.0.0 for default gateway.

        ("ipRouteMask")

    $info->ipr_info()
        Reference to MIB definition specific to routing protocol.

        ("ipRouteInfo")

  Setting data via SNMP

    This section explains how to use SNMP::Info to do SNMP Set operations.

    $info->set_METHOD($value)
        Sets the global METHOD to value. Assumes that iid is .0

        Returns undef if failed, or the return value from
        SNMP::Session::set() (snmp_errno)

         $info->set_location("Here!");

    $info->set_METHOD($value,$iid)
        Table Methods. Set iid of method to value.

        Returns undef if failed, or the return value from
        SNMP::Session::set() (snmp_errno)

         # Disable a port administratvely
         my %if_map = reverse %{$info->interfaces()}
         $info->set_i_up_admin('down', $if_map{'FastEthernet0/0') 
            or die "Couldn't disable the port. ",$info->error(1);

    NOTE: You must be connected to your device with a ReadWrite community
    string in order for set operations to work.

    NOTE: This will only set data listed in %FUNCS and %GLOBALS. For data
    aquired from overriden methods (subroutines) specific set_METHOD()
    subroutines will need to be added.

  Quiet Mode

    SNMP::Info will not chirp anything to STDOUT unless there is a serious
    error (in which case it will probably die).

    To get lots of debug info, set the Debug flag when calling new() or call
    $info->debug(1);

    When calling a method check the return value. If the return value is
    undef then check $info->error()

    Beware, calling $info->error() clears the error.

     my $name = $info->name() or die "Couldn't get sysName!" . $name->error();

EXTENDING SNMP::INFO

  Data Structures required in new Subclass

    A class inheriting this class must implement these data structures :

    $INIT
        Used to flag if the MIBs have been loaded yet.

    %GLOBALS
        Contains a hash in the form ( method_name => SNMP iid name ) These
        are scalar values such as name,uptime, etc.

        When choosing the name for the methods, be aware that other new Sub
        Modules might inherit this one to get it's features. Try to choose a
        prefix for methods that will give it's own name space inside the
        SNMP::Info methods.

    %FUNCS
        Contains a hash in the form ( method_name => SNMP iid) These are
        table entries, such as the IfIndex

    %MIBS
        A list of each mib needed.

        ('MIB-NAME' => 'itemToTestForPresence')

        The value for each entry should be a MIB object to check for to make
        sure that the MIB is present and has loaded correctly.

        $info->init() will throw an exception if a MIB does not load.

    %MUNGE
        A map between method calls (from %FUNCS or %GLOBALS) and subroutine
        methods. The subroutine called will be passed the data as it gets it
        from SNMP and it should return that same data in a more human
        friendly format.

        Sample %MUNGE:

         (my_ip     => \&munge_ip,
          my_mac    => \&munge_mac,
          my_layers => \&munge_dec2bin
         )

  Sample Subclass

    Let's make a sample Layer 2 Device subclass :

    ----------------------- snip --------------------------------

     # SNMP::Info::Layer2::Sample

     package SNMP::Info::Layer2::Sample;

     $VERSION = 0.1;

     use strict;

     use Exporter;
     use SNMP::Info::Layer2;

     @SNMP::Info::Layer2::Sample::ISA = qw/SNMP::Info::Layer2 Exporter/;
     @SNMP::Info::Layer2::Sample::EXPORT_OK = qw//;

     use vars qw/$VERSION %FUNCS %GLOBALS %MIBS %MUNGE $AUTOLOAD $INIT $DEBUG/;

     %MIBS    = (%SNMP::Info::Layer2::MIBS,
                 'SUPER-DOOPER-MIB'  => 'supermibobject'
                );

     %GLOBALS = (%SNMP::Info::Layer2::GLOBALS,
                 'name'              => 'supermib_supername',
                 'favorite_color'    => 'supermib_fav_color_object',
                 'favorite_movie'    => 'supermib_fav_movie_val'
                 );

     %FUNCS   = (%SNMP::Info::Layer2::FUNCS,
                 # Super Dooper MIB - Super Hero Table
                 'super_hero_index'  => 'SuperHeroIfIndex',
                 'super_hero_name'   => 'SuperHeroIfName',
                 'super_hero_powers' => 'SuperHeroIfPowers'
                );

     %MUNGE   = (%SNMP::Info::Layer2::MUNGE,
                 'super_hero_powers' => \&munge_powers
                );

     # OverRide uptime() method from %SNMP::Info::GLOBALS
     sub uptime {
         my $sample = shift;

         my $name   = $sample->name();

         # this is silly but you get the idea
         return '600' if defined $name ; 
     }

     # Create our own munge function
     sub munge_powers {
         my $power = shift;

         # Take the returned obscure value and return something useful.
         return 'Fire' if $power =~ /reallyhot/i;
         return 'Ice'  if $power =~ /reallycold/i;

         # Else 
         return $power;
     }

     # Copious Documentation here!!!
     =head1 NAME
     =head1 AUTHOR
     =head1 SYNOPSIS
     =head1 DESCRIPTION
     =head2 Inherited Classes
     =head2 Required MIBs
     =head1 GLOBALS
     =head2 Overrides
     =head1 TABLE METHODS
     =head2 Overrides
     =cut

     1; # don't forget this line
    ----------------------- snip --------------------------------

    Be sure and send the debugged version to snmp@warped.org to be included
    in the next version of SNMP::Info.

SNMP::INFO INTERNALS

  Object Namespace

    Internal data is stored with bareword keys. For example $info->{debug}

    SNMP Data is stored or marked cached with keys starting with an
    underscore. For example $info->{_name} is the cache for $info->name().

    Cached Table data is stored in $info->store() and marked cached per
    above.

  Package Globals

    These set the default value for an object upon creation.

    $DEBUG
        Default 0. Sends copious debug info to stdout. This global sets the
        object's debug status in new() unless 'Debug' argument passed in
        new(). Change objects' debug status with $info->debug().

    $BIGINT
        Default 0. Set to true to have 64 bit counters return Math::BigInt
        objects instead of scalar string values. See note under Interface
        Statistics about 64 bit values.

    $NOSUCH
        Default 1. Set to false to disable RetryNoSuch option for
        SNMP::Session. Or see method in new() to do it on an object scope.

  Data Munging Callback Subroutines

    munge_speed()
        Makes human friendly speed ratings using %SPEED_MAP

         %SPEED_MAP = (
                        '56000'      => '56 kbps',
                        '64000'      => '64 kbps',
                        '1500000'    => '1.5 Mbps',
                        '1536000'    => 'T1',      
                        '1544000'    => 'T1',
                        '2000000'    => '2.0 Mbps',
                        '2048000'    => '2.048 Mbps',
                        '3072000'    => 'Dual T1',
                        '3088000'    => 'Dual T1',   
                        '4000000'    => '4.0 Mbps',
                        '10000000'   => '10 Mbps',
                        '11000000'   => '11 Mbps',
                        '20000000'   => '20 Mbps',
                        '16000000'   => '16 Mbps',
                        '44210000'   => 'T3',
                        '44736000'   => 'T3',
                        '45000000'   => '45 Mbps',
                        '45045000'   => 'DS3',
                        '64000000'   => '64 Mbps',
                        '100000000'  => '100 Mbps',
                        '149760000'  => 'ATM on OC-3',
                        '155000000'  => 'OC-3',
                        '155519000'  => 'OC-3',
                        '155520000'  => 'OC-3',
                        '400000000'  => '400 Mbps',
                        '599040000'  => 'ATM on OC-12', 
                        '622000000'  => 'OC-12',
                        '622080000'  => 'OC-12',
                        '1000000000' => '1.0 Gbps',
                     )

    munge_ip()
        Takes a binary IP and makes it dotted ASCII

    munge_mac()
        Takes an octet stream (HEX-STRING) and returns a colon separated
        ASCII hex string.

    munge_octet2hex()
        Takes a binary octet stream and returns an ASCII hex string

    munge_dec2bin()
        Takes a binary char and returns its ASCII binary representation

    munge_bits
        Takes a SNMP2 'BITS' field and returns the ASCII bit string

    munge_counter64
        If $BIGINT is set to true, then a Math::BigInt object is returned.
        See Math::BigInt for details.

  Internaly Used Functions

    $info->init()
        Used internally. Loads all entries in %MIBS.

    $info->args()
        Returns a reference to the argument hash supplied to SNMP::Session

    $info->class()
        Returns the class name of the object.

    $info->error_throw(error message)
        Stores the error message for use by $info->error()

        If $info->debug() is true, then the error message is carped too.

    $info->funcs()
        Returns a reference to the %FUNCS hash.

    $info->globals()
        Returns a reference to the %GLOBALS hash.

    $info->mibs()
        Returns a reference to the %MIBS hash.

    $info->munge()
        Returns a reference ot the %MUNGE hash.

    $info->nosuch()
        Returns NoSuch value set or not in new()

    $info->session()
        Gets or Sets the SNMP::Session object.

    $info->store(new_store)
        Returns or sets hash store for Table functions.

        Store is a hash reference in this format :

        $info->store = { attribute => { iid => value , iid2 => value2, ... }
        };

    $info->_global()
        Used internally by AUTOLOAD to load dynmaic methods from %GLOBALS.

        Example: $info->name() calls autoload which calls
        $info->_global('name').

    $info->_set(attr,val,iid)
        Used internally by AUTOLOAD to run an SNMP set command for dynamic
        methods listed in either %GLOBALS or %FUNCS.

        Example: $info->set_name('dog',3) uses autoload to resolve to
        $info->_set('name','dog',3);

    $info->load_all()
        Debugging routine. This does not include any overriden method or
        method implemented by subroutine.

        Runs $info->load_METHOD() for each entry in $info->funcs();

        Returns $info->store() -- See store() entry.

        Note return value has changed since version 0.3

    $info->all()
        Runs $info->load_all() once then returns $info->store();

        Use $info->load_all() to reload the data.

        Note return value has changed since version 0.3

    $info->_load_attr()
        Used internally by AUTOLOAD to fetch data called from methods listed
        in %FUNCS.

        Called from $info->load_METHOD();

    $info->_show_attr()
        Used internaly by AUTOLOAD to return data called by methods listed
        in %FUNCS.

        Called like $info->METHOD().

        The first time ran, it will call $info->load_METHOD(). Every time
        after it will return cached data.

  AUTOLOAD

    Each entry in either %FUNCS or %GLOBALS is used by AUTOLOAD() to create
    dynamic methods.

    Note that this AUTOLOAD is going to be run for all the classes listed in
    the @ISA array in a subclass, so will be called with a variety of
    package names. We check the %FUNCS and %GLOBALS of the package that is
    doing the calling at this given instant.

    1. Returns unless method is listed in %FUNCS or %GLOBALS for given class
    2. If the method exists in %GLOBALS it runs $info->_global(method)
    unless already cached.
    3. Method is in %FUNCS
    4. Run $info->_load_attr(method) if not cached
    5. Return $info->_show_attr(method).

    Override any dynamic method listed in one of these hashes by creating a
    subroutine with the same name.

    For example to override $info->name() create `` sub name {...}'' in your
    subclass.

COPYRIGHT AND LICENCE

    Changes from SNMP::Info Version 0.7 and on are: Copyright (c)2003, 2004
    Max Baker - All rights reserved.

    Original Code is: Copyright (c) 2002-3, Regents of the University of
    California All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

        * Redistributions of source code must retain the above copyright notice,
          this list of conditions and the following disclaimer.
        * Redistributions in binary form must reproduce the above copyright notice,
          this list of conditions and the following disclaimer in the documentation
          and/or other materials provided with the distribution.
        * Neither the name of the University of California, Santa Cruz nor the 
          names of its contributors may be used to endorse or promote products 
          derived from this software without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
    IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
    TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
    PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
    OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

