       BridgeQuery polls a device which respond to SNMP Bridge
       Table queries and generates a hash reference with each
       polled MAC address as the key and the associated port as
       the value.  The specific MIBs that are polled are
       described in RFC1493.

       SNMP::BridgeQuery requires Net::SNMP in order to function.

       Devices can be switches, bridges, or most anything that
       responds as a OSI Layer 2 component.  Layer 3 devices do
       not generally respond and will cause an error.  If an
       error is generated, it will return a hash reference with a
       single element ('error') which can be tested for.

       Two other functions (querymacs & queryports) can be
       explicitly exported.  They work the same way as queryfdb,
       but they return MAC addresses or ports (respectively) with
       the SNMP MIB as the hash key.

       A newly added function (queryat) can be used on layer 3
       switches to poll the Address Translation Tables.  This is
       similar to the data returned by the 'queryfdb' function,
       but it returns the IP address of the device and the
       associated interface (separated by a pipe '|') with the
       MAC address as the key.  On a layer 3 switch, this
       interface probably does not correspond to a physical port,
       but more likely referrs to a vlan ID.  Using this function
       on a layer 2 device will generate a 'trapped' error.


