entPhysicalClass

An enumerated value which provides an indication of the
general hardware type of a particular physical entity.
There are no restrictions as to the number of
entPhysicalEntries of each entPhysicalClass, which must be
instantiated by an agent.
          
The enumeration 'other' is applicable if the physical entity
class is known, but does not match any of the supported
values.
          
The enumeration 'unknown' is applicable if the physical
entity class is unknown to the agent.
          
The enumeration 'chassis' is applicable if the physical
entity class is an overall container for networking
equipment.  Any class of physical entity except a stack may
be contained within a chassis, and a chassis may only be
contained within a stack.
          
The enumeration 'backplane' is applicable if the physical
entity class is some sort of device for aggregating and
forwarding networking traffic, such as a shared backplane in
a modular ethernet switch.  Note that an agent may model a
backplane as a single physical entity, which is actually
implemented as multiple discrete physical components (within
a chassis or stack).
          
The enumeration 'container' is applicable if the physical
entity class is capable of containing one or more removable
physical entities, possibly of different types. For example,
each (empty or full) slot in a chassis will be modeled as a
container. Note that all removable physical entities should
be modeled within a container entity, such as field-
replaceable modules, fans, or power supplies.  Note that all
known containers should be modeled by the agent, including
empty containers.
          
The enumeration 'powerSupply' is applicable if the physical
entity class is a power-supplying component.
          
The enumeration 'fan' is applicable if the physical entity
class is a fan or other heat-reduction component.
          
The enumeration 'sensor' is applicable if the physical
entity class is some sort of sensor, such as a temperature
sensor within a router chassis.
          
The enumeration 'module' is applicable if the physical
entity class is some sort of self-contained sub-system.  If
it is removable, then it should be modeled within a
container entity, otherwise it should be modeled directly
within another physical entity (e.g., a chassis or another
module).
          
The enumeration 'port' is applicable if the physical entity
class is some sort of networking port, capable of receiving
and/or transmitting networking traffic.
          
The enumeration 'stack' is applicable if the physical entity
class is some sort of super-container (possibly virtual),
intended to group together multiple chassis entities.  A
stack may be realized by a 'virtual' cable, a real
interconnect cable, attached to multiple chassis, or may in
fact be comprised of multiple interconnect cables. A stack
should not be modeled within any other physical entities,
but a stack may be contained within another stack.  Only
chassis entities should be contained within a stack.