This document is obsolete. Please
refer to RFC 2737.
Network Working Group K. McCloghrie Request for Comments: 2037 A. Bierman Category: Standards Track Cisco Systems October 1996
Entity MIB using SMIv2
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Table of Contents
1. Introduction .............................................. 2 2. The SNMP Network Management Framework ..................... 2 2.1 Object Definitions ....................................... 2 3. Overview .................................................. 3 3.1 Terms .................................................... 4 3.2 Relationship to Community Strings ........................ 5 3.3 Relationship to Proxy Mechanisms ......................... 5 3.4 Relationship to a Chassis MIB ............................ 5 3.5 Relationship to the Interfaces MIB ....................... 6 3.6 Relationship to the Other MIBs ........................... 6 3.7 Relationship to Naming Scopes ............................ 6 3.8 Multiple Instances of the Entity MIB ..................... 7 3.9 Re-Configuration of Entities ............................. 7 3.10 MIB Structure ........................................... 7 3.10.1 entityPhysical Group .................................. 8 3.10.2 entityLogical Group ................................... 8 3.10.3 entityMapping Group ................................... 8 3.10.4 entityGeneral Group ................................... 9 3.10.5 entityNotifications Group ............................. 9 3.11 Multiple Agents ......................................... 9 4. Definitions ............................................... 10 5. Usage Examples ............................................ 26 5.1 Router/Bridge ............................................ 26 5.2 Repeaters ................................................ 30 6. Acknowledgements .......................................... 33 7. References ................................................ 34 8. Security Considerations ................................... 35 9. Authors' Addresses ........................................ 35
This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it describes managed objects used for managing multiple logical and physical entities managed by a single SNMP agent.
The SNMP Network Management Framework presently consists of three major components. They are:
o the SMI, described in RFC 1902 [1], - the mechanisms used for describing and naming objects for the purpose of management.
o the MIB-II, STD 17, RFC 1213 [2], - the core set of managed objects for the Internet suite of protocols.
o the protocol, RFC 1157 [6] and/or RFC 1905 [4], - the protocol for accessing managed information.
Textual conventions are defined in RFC 1903 [3], and conformance statements are defined in RFC 1904 [5].
The Framework permits new objects to be defined for the purpose of experimentation and evaluation.
This memo specifies a MIB module that is compliant to the SNMPv2 SMI. A semantically identical MIB conforming to the SNMPv1 SMI can be produced through the appropriate translation.
Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. Objects in the MIB are defined using the subset of Abstract Syntax Notation One (ASN.1) defined in the SMI. In particular, each object type is named by an OBJECT IDENTIFIER, an administratively assigned name. The object type together with an object instance serves to uniquely identify a specific instantiation of the object. For human convenience, we often use a textual string, termed the descriptor, to refer to the object type.
There is a need for a standardized way of representing a single agent which supports multiple instances of one MIB. This is presently true for at least 3 standard MIBs, and is likely to become true for more and more MIBs as time passes. For example:
- multiple instances of a bridge supported within a single device having a single agent;
- multiple repeaters supported by a single agent;
- multiple OSPF backbone areas, each one operating as part of its own Autonomous System, and each identified by the same area-id (e.g., 0.0.0.0), supported inside a single router with one agent.
The fact that it is a single agent in each of these cases implies there is some relationship which binds all of these entities together. Effectively, there is some "overall" physical entity which houses the sum of the things managed by that one agent, i.e., there are multiple "logical" entities within a single physical entity. Sometimes, the overall physical entity contains multiple (smaller) physical entities and each logical entity is associated with a particular physical entity. Sometimes, the overall physical entity is a "compound" of multiple physical entities (e.g., a stack of stackable hubs).
What is needed is a way to determine exactly what logical entities are managed by the agent (either by SNMPv1 or SNMPv2), and thereby to be able to communicate with the agent about a particular logical entity. When different logical entities are associated with different physical entities within the overall physical entity, it is also useful to be able to use this information to distinguish between logical entities.
In these situations, there is no need for varbinds for multiple logical entities to be referenced in the same SNMP message (although that might be useful in the future). Rather, it is sufficient, and in some situations preferable, to have the context/community in the message identify the logical entity to which the varbinds apply.
- Naming Scope A "naming scope" represents the set of information that may be potentially accessed through a single SNMP operation. All instances within the naming scope share the same unique identifier space. For SNMPv1, a naming scope is identified by the value of the associated 'entLogicalCommunity' instance.
- Multi-Scoped Object A MIB object, for which identical instance values identify different managed information in different naming scopes, is called a "multi-scoped" MIB object.
- Single-Scoped Object A MIB object, for which identical instance values identify the same managed information in different naming scopes, is called a "single-scoped" MIB object.
- Logical Entity A managed system contains one or more logical entities, each represented by at most one instantiation of each of a particular set of MIB objects. A set of management functions is associated with each logical entity. Examples of logical entities include routers, bridges, print-servers, etc.
- Physical Entity A "physical entity" or "physical component" represents an identifiable physical resource within a managed system. Zero or more logical entities may utilize a physical resource at any given time. It is an implementation-specific manner as to which physical components are represented by an agent in the EntPhysicalTable. Typically, physical resources (e.g. communications ports, backplanes, sensors, daughter-cards, power supplies, the overall chassis) which can be managed via functions associated with one or more logical entities are included in the MIB.
- Containment Tree Each physical component may optionally be modeled as 'contained' within another physical component. A "containment-tree" is the conceptual sequence of entPhysicalIndex values which uniquely specifies the exact physical location of a physical component within the managed system. It is generated by 'following and recording' each 'entPhysicalContainedIn' instance 'up the tree towards the root', until a value of zero indicating no further containment is found.
McCloghrie & Bierman Standards Track [Page 4]
RFC 2037 Entity MIB using SMIv2 October 1996
Note that chassis slots, which are capable of accepting one or more module types from one or more vendors, are modeled as containers in this MIB. The value of entPhysicalContainedIn for a particular 'module' entity (entPhysicalClass value of 'module(9)') must be equal to an entPhysicalIndex that represents the parent 'container' entity (associated entPhysicalClass value of ('container(5)'). An agent must represent both empty and full containers in the entPhysicalTable.
For community-based SNMP, distinguishing between different logical entities is one (but not the only) purpose of the community string [6]. This is accommodated by representing each community string as a logical entity.
Note that different logical entities may share the same naming scope (and therefore the same values of entLogicalCommunity). This is possible, providing they have no need for the same instance of a MIB object to represent different managed information.
The Entity MIB is designed to allow functional component discovery. The administrative relationships between different logical entities are not visible in any Entity MIB tables. An NMS cannot determine whether MIB instances in different naming scopes are realized locally or remotely (e.g. via some proxy mechanism) by examining any particular Entity MIB objects.
The management of administrative framework functions is not an explicit goal of the Entity MIB WG at this time. This new area of functionality may be revisited after some operational experience with the Entity MIB is gained.
Note that a network administrator will likely be able to associate community strings with naming scopes with proprietary mechanisms, as a matter of configuration. There are no mechanisms for managing naming scopes defined in this MIB.
Some readers may recall that a previous IETF working group attempted to define a Chassis MIB. No consensus was reached by that working group, possibly because its scope was too broad. As such, it is not the purpose of this MIB to be a "Chassis MIB replacement", nor is it within the scope of this MIB to contain all the information which might be necessary to manage a "chassis". On the other hand, the
McCloghrie & Bierman Standards Track [Page 5]
RFC 2037 Entity MIB using SMIv2 October 1996
entities represented by an implementation of this MIB might well be contained in a chassis.
The Entity MIB contains a mapping table identifying physical components that have 'external values' (e.g. ifIndex) associated with them within a given naming scope. This table can be used to identify the physical location of each interface in the ifTable [7]. Since ifIndex values in different contexts are not related to one another, the interface to physical component associations are relative to the same logical entity within the agent.
The Entity MIB also contains an 'entPhysicalName' object, which approximates the semantics of the ifName object from the Interfaces MIB [7] for all types of physical components.
The Entity MIB contains a mapping table identifying physical components that have identifiers from other standard MIBs associated with them. For example, this table can be used along with the physical mapping table to identify the physical location of each repeater port in the rptrPortTable, or each interface in the ifTable.
There is some question as to which MIB objects may be returned within a given naming scope. MIB objects which are not multi-scoped within a managed system are likely to ignore context information in implementation. In such a case, it is likely such objects will be returned in all naming scopes (e.g. not just the 'main' naming scope).
For example, a community string used to access the management information for logical device 'bridge2' may allow access to all the non-bridge related objects in the 'main' naming scope, as well as a second instance of the Bridge MIB.
It is an implementation-specific matter as to the isolation of single-scoped MIB objects by the agent. An agent may wish to limit the objects returned in a particular naming scope to just the multi- scoped objects in that naming scope (e.g. system group and the Bridge MIB). In this case, all single-scoped management information would belong to a common naming scope (e.g. 'main'), which itself may contain some multi-scoped objects (e.g. system group).
It is possible that more than one agent exists in a managed system, and in such cases, multiple instances of the Entity MIB (representing the same managed objects) may be available to an NMS.
In order to reduce complexity for agent implementation, multiple instances of the Entity MIB are not required to be equivalent or even consistent. An NMS may be able to 'align' instances returned by different agents by examining the columns of each table, but vendor- specific identifiers and (especially) index values are likely to be different. Each agent may be managing different subsets of the entire chassis as well.
When all of a physically-modular device is represented by a single agent, the entry for which entPhysicalContainedIn has the value zero would likely have 'chassis' as the value of its entPhysicalClass; alternatively, for an agent on a module where the agent represents only the physical entities on that module (not those on other modules), the entry for which entPhysicalContainedIn has the value zero would likely have 'module' as the value of its entPhysicalClass.
An agent implementation of the entLogicalTable is not required to contain information about logical entities managed primarily by other agents. That is, the entLogicalTAddress and entLogicalTDomain objects in the entLogicalTable are provided to support an historical multiplexing mechanism, not to identify other SNMP agents.
Note that the Entity MIB is a single-scoped MIB, in the event an agent represents the MIB in different naming scopes.
All the MIB objects defined in this MIB have at most a read-only MAX-ACCESS clause, i.e., none are write-able. This is a conscious decision by the working group to limit this MIB's scope. It is possible that this restriction could be lifted after implementation experience, by means of additional tables (using the AUGMENTS clause) for configuration and extended entity information.
- entityPhysical group Describes the physical entities managed by a single agent.
McCloghrie & Bierman Standards Track [Page 7]
RFC 2037 Entity MIB using SMIv2 October 1996
- entityLogical group Describes the logical entities managed by a single agent.
- entityMapping group Describes the associations between the physical entities, logical entities, interfaces, and non-interface ports managed by a single agent.
-entityGeneral group Describes general system attributes shared by potentially all types of entities managed by a single agent.
-entityNotifications group Contains status indication notifications.
This group contains a single table to identify physical system components, called the entPhysicalTable.
The entPhysicalTable contains one row per physical entity, and must always contains at least one row for an "overall" physical entity. Each row is indexed by an arbitrary, small integer, and contains a description and type of the physical entity. It also optionally contains the index number of another entPhysicalEntry indicating a containment relationship between the two.
This group contains a single table to identify logical entities, called the entLogicalTable.
The entLogicalTable contains one row per logical entity. Each row is indexed by an arbitrary, small integer and contains a name, description, and type of the logical entity. It also contains information to allow SNMPv1 or SNMPv2C [9] access to the MIB information for the logical entity.
This group contains a three tables to identify associations between different system components.
The entLPMappingTable contains mappings between entLogicalIndex values (logical entities) and entPhysicalIndex values (the physical components supporting that entity). A logical entity can map to more than one physical component, and more than one logical entity can map to (share) the same physical component.
McCloghrie & Bierman Standards Track [Page 8]
RFC 2037 Entity MIB using SMIv2 October 1996
The entAliasMappingTable contains mappings between entLogicalIndex, entPhysicalIndex pairs and 'alias' object identifier values. This allows resources managed with other MIBs (e.g. repeater ports, bridge ports, physical and logical interfaces) to be identified in the physical entity hierarchy. Note that each alias identifier is only relevant in a particular naming scope.
The entPhysicalContainsTable contains simple mappings between 'entPhysicalContainedIn' values for each container/containee relationship in the managed system. The indexing of this table allows an NMS to quickly discover the 'entPhysicalIndex' values for all children of a given physical entity.
This group contains general information relating to the other object groups.
At this time, the entGeneral group contains a single scalar object (entLastChangeTime), which represents the value of sysUptime when any part of the system configuration last changed.
Even though a primary motivation for this MIB is to represent the multiple logical entities supported by a single agent, it is also possible to use it to represent multiple logical entities supported by multiple agents (in the same "overall" physical entity). Indeed, it is implicit in the SNMP architecture, that the number of agents is transparent to a network management station.
However, there is no agreement at this time as to the degree of cooperation which should be expected for agent implementations. Therefore, multiple agents within the same managed system are free to implement the Entity MIB independently. (Refer the section on "Multiple Instances of the Entity MIB" for more details).
IMPORTS MODULE-IDENTITY, OBJECT-TYPE, mib-2, NOTIFICATION-TYPE FROM SNMPv2-SMI TDomain, TAddress, DisplayString, TEXTUAL-CONVENTION, AutonomousType, RowPointer, TimeStamp FROM SNMPv2-TC MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF;
entityMIB MODULE-IDENTITY LAST-UPDATED "9605160000Z" ORGANIZATION "IETF ENTMIB Working Group" CONTACT-INFO " WG E-mail: entmib@cisco.com Subscribe: majordomo@cisco.com msg body: subscribe entmib
Keith McCloghrie ENTMIB Working Group Chair Cisco Systems Inc. 170 West Tasman Drive San Jose, CA 95134 408-526-5260 kzm@cisco.com
Andy Bierman ENTMIB Working Group Editor Cisco Systems Inc. 170 West Tasman Drive San Jose, CA 95134 408-527-3711 abierman@cisco.com" DESCRIPTION "The MIB module for representing multiple logical entities supported by a single SNMP agent." ::= { mib-2 47 }
-- Textual Conventions PhysicalIndex ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "An arbitrary value which uniquely identifies the physical entity. The value is a small positive integer; index values for different physical entities are not necessarily contiguous." SYNTAX INTEGER (1..2147483647)
PhysicalClass ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "An enumerated value which provides an indication of the general hardware type of a particular physical entity." SYNTAX INTEGER { other(1), unknown(2), chassis(3), backplane(4), container(5), -- e.g. slot or daughter-card holder powerSupply(6), fan(7), sensor(8), module(9), -- e.g. plug-in card or daughter-card port(10) }
-- The Physical Entity Table
entPhysicalTable OBJECT-TYPE SYNTAX SEQUENCE OF EntPhysicalEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "This table contains one row per physical entity. There is always at least one row for an 'overall' physical entity." ::= { entityPhysical 1 }
entPhysicalEntry OBJECT-TYPE SYNTAX EntPhysicalEntry MAX-ACCESS not-accessible STATUS current
McCloghrie & Bierman Standards Track [Page 11]
RFC 2037 Entity MIB using SMIv2 October 1996
DESCRIPTION "Information about a particular physical entity.
Each entry provides objects (entPhysicalDescr, entPhysicalVendorType, and entPhysicalClass) to help an NMS identify and characterize the entry, and objects (entPhysicalContainedIn and entPhysicalParentRelPos) to help an NMS relate the particular entry to other entries in this table." INDEX { entPhysicalIndex } ::= { entPhysicalTable 1 }
entPhysicalIndex OBJECT-TYPE SYNTAX PhysicalIndex MAX-ACCESS not-accessible STATUS current DESCRIPTION "The index for this entry." ::= { entPhysicalEntry 1 }
entPhysicalDescr OBJECT-TYPE SYNTAX DisplayString MAX-ACCESS read-only STATUS current DESCRIPTION "A textual description of physical entity. This object should contain a string which identifies the manufacturer's name for the physical entity, and should be set to a distinct value for each version or model of the physical entity. " ::= { entPhysicalEntry 2 }
entPhysicalVendorType OBJECT-TYPE SYNTAX AutonomousType MAX-ACCESS read-only STATUS current DESCRIPTION "An indication of the vendor-specific hardware type of the
McCloghrie & Bierman Standards Track [Page 12]
RFC 2037 Entity MIB using SMIv2 October 1996
physical entity. Note that this is different from the definition of MIB-II's sysObjectID.
An agent should set this object to a enterprise-specific registration identifier value indicating the specific equipment type in detail. The associated instance of entPhysicalClass is used to indicate the general type of hardware device.
If no vendor-specific registration identifier exists for this physical entity, or the value is unknown by this agent, then the value { 0 0 } is returned." ::= { entPhysicalEntry 3 }
entPhysicalContainedIn OBJECT-TYPE SYNTAX INTEGER (0..2147483647) MAX-ACCESS read-only STATUS current DESCRIPTION "The value of entPhysicalIndex for the physical entity which 'contains' this physical entity. A value of zero indicates this physical entity is not contained in any other physical entity. Note that the set of 'containment' relationships define a strict hierarchy; that is, recursion is not allowed." ::= { entPhysicalEntry 4 }
entPhysicalClass OBJECT-TYPE SYNTAX PhysicalClass MAX-ACCESS read-only STATUS current DESCRIPTION "An indication of the general hardware type of the physical entity.
An agent should set this object to the standard enumeration value which most accurately indicates the general class of the physical entity, or the primary class if there is more than one.
If no appropriate standard registration identifier exists for this physical entity, then the value 'other(1)' is returned. If the value is unknown by this agent, then the value 'unknown(2)' is returned." ::= { entPhysicalEntry 5 }
MAX-ACCESS read-only STATUS current DESCRIPTION "An indication of the relative position of this 'child' component among all its 'sibling' components. Sibling components are defined as entPhysicalEntries which share the same instance values of each of the entPhysicalContainedIn and entPhysicalClass objects.
An NMS can use this object to identify the relative ordering for all sibling components of a particular parent (identified by the entPhysicalContainedIn instance in each sibling entry).
This value should match any external labeling of the physical component if possible. For example, for a module labeled as 'card #3', entPhysicalParentRelPos should have the value '3'.
If the physical position of this component does not match any external numbering or clearly visible ordering, then user documentation or other external reference material should be used to determine the parent-relative position. If this is not possible, then the the agent should assign a consistent (but possibly arbitrary) ordering to a given set of 'sibling' components, perhaps based on internal representation of the components.
If the agent cannot determine the parent-relative position for some reason, or if the associated value of entPhysicalContainedIn is '0', then the value '-1' is returned. Otherwise a non-negative integer is returned, indicating the parent-relative position of this physical entity.
Parent-relative ordering normally starts from '1' and continues to 'N', where 'N' represents the highest positioned child entity. However, if the physical entities (e.g. slots) are labeled from a starting position of zero, then the first sibling should be associated with a entPhysicalParentRelPos value of '0'. Note that this ordering may be sparse or dense, depending on agent implementation.
The actual values returned are not globally meaningful, as each 'parent' component may use different numbering algorithms. The ordering is only meaningful among siblings of the same parent component.
McCloghrie & Bierman Standards Track [Page 14]
RFC 2037 Entity MIB using SMIv2 October 1996
The agent should retain parent-relative position values across reboots, either through algorithmic assignment or use of non-volatile storage." ::= { entPhysicalEntry 6 }
entPhysicalName OBJECT-TYPE SYNTAX DisplayString MAX-ACCESS read-only STATUS current DESCRIPTION "The textual name of the physical entity. The value of this object should be the name of the component as assigned by the local device and should be suitable for use in commands entered at the device's `console'. This might be a text name, such as `console' or a simple component number (e.g. port or module number), such as `1', depending on the physical component naming syntax of the device.
If there is no local name, or this object is otherwise not applicable, then this object contains a zero-length string.
Note that the value of entPhysicalName for two physical entities will be the same in the event that the console interface does not distinguish between them, e.g., slot-1 and the card in slot-1." ::= { entPhysicalEntry 7 }
-- The Logical Entity Table entLogicalTable OBJECT-TYPE SYNTAX SEQUENCE OF EntLogicalEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "This table contains one row per logical entity. At least one entry must exist." ::= { entityLogical 1 }
entLogicalEntry OBJECT-TYPE SYNTAX EntLogicalEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "Information about a particular logical entity. Entities may be managed by this agent or other SNMP agents (possibly) in the same chassis." INDEX { entLogicalIndex } ::= { entLogicalTable 1 }
entLogicalIndex OBJECT-TYPE SYNTAX INTEGER (1..2147483647) MAX-ACCESS not-accessible STATUS current DESCRIPTION "The value of this object uniquely identifies the logical entity. The value is a small positive integer; index values for different logical entities are are not necessarily contiguous." ::= { entLogicalEntry 1 }
entLogicalDescr OBJECT-TYPE SYNTAX DisplayString MAX-ACCESS read-only STATUS current DESCRIPTION "A textual description of the logical entity. This object should contain a string which identifies the manufacturer's name for the logical entity, and should be set to a distinct value for each version of the logical entity. " ::= { entLogicalEntry 2 }
entLogicalType OBJECT-TYPE SYNTAX AutonomousType MAX-ACCESS read-only STATUS current DESCRIPTION "An indication of the type of logical entity. This will typically be the OBJECT IDENTIFIER name of the node in the SMI's naming hierarchy which represents the major MIB module, or the majority of the MIB modules, supported by the logical entity. For example: a logical entity of a regular host/router -> mib-2 a logical entity of a 802.1d bridge -> dot1dBridge a logical entity of a 802.3 repeater -> snmpDot3RptrMgmt If an appropriate node in the SMI's naming hierarchy cannot be identified, the value 'mib-2' should be used." ::= { entLogicalEntry 3 }
McCloghrie & Bierman Standards Track [Page 16]
RFC 2037 Entity MIB using SMIv2 October 1996
entLogicalCommunity OBJECT-TYPE SYNTAX OCTET STRING (SIZE (1..255)) MAX-ACCESS read-only STATUS current DESCRIPTION "An SNMPv1 or SNMPv2C community-string which can be used to access detailed management information for this logical entity. The agent should allow read access with this community string (to an appropriate subset of all managed objects) and may also choose to return a community string based on the privileges of the request used to read this object. Note that an agent may choose to return a community string with read-only privileges, even if this object is accessed with a read-write community string. However, the agent must take care not to return a community string which allows more privileges than the community string used to access this object.
A compliant SNMP agent may wish to conserve naming scopes by representing multiple logical entities in a single 'main' naming scope. This is possible when the logical entities represented by the same value of entLogicalCommunity have no object instances in common. For example, 'bridge1' and 'repeater1' may be part of the main naming scope, but at least one additional community string is needed to represent 'bridge2' and 'repeater2'.
Logical entities 'bridge1' and 'repeater1' would be represented by sysOREntries associated with the 'main' naming scope.
For agents not accessible via SNMPv1 or SNMPv2C, the value of this object is the empty-string." ::= { entLogicalEntry 4 }
entLogicalTAddress OBJECT-TYPE SYNTAX TAddress MAX-ACCESS read-only STATUS current DESCRIPTION "The transport service address by which the logical entity receives network management traffic, formatted according to the corresponding value of entLogicalTDomain.
For snmpUDPDomain, a TAddress is 6 octets long, the initial 4 octets containing the IP-address in network-byte order and the last 2 containing the UDP port in network-byte order. Consult 'Transport Mappings for Version 2 of the Simple
McCloghrie & Bierman Standards Track [Page 17]
RFC 2037 Entity MIB using SMIv2 October 1996
Network Management Protocol' (RFC 1906 [8]) for further information on snmpUDPDomain." ::= { entLogicalEntry 5 }
entLogicalTDomain OBJECT-TYPE SYNTAX TDomain MAX-ACCESS read-only STATUS current DESCRIPTION "Indicates the kind of transport service by which the logical entity receives network management traffic. Possible values for this object are presently found in the Transport Mappings for SNMPv2 document (RFC 1906 [8])." ::= { entLogicalEntry 6 }
entLPMappingTable OBJECT-TYPE SYNTAX SEQUENCE OF EntLPMappingEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "This table contains zero or more rows of logical entity to physical equipment associations. For each logical entity known by this agent, there are zero or more mappings to the physical resources which are used to realize that logical entity.
An agent should limit the number and nature of entries in this table such that only meaningful and non-redundant information is returned. For example, in a system which contains a single power supply, mappings between logical entities and the power supply are not useful and should not be included.
Also, only the most appropriate physical component which is closest to the root of a particular containment tree should be identified in an entLPMapping entry.
For example, suppose a bridge is realized on a particular module, and all ports on that module are ports on this bridge. A mapping between the bridge and the module would be useful, but additional mappings between the bridge and each of the ports on that module would be redundant (since the entPhysicalContainedIn hierarchy can provide the same information). If, on the other hand, more than one bridge was utilizing ports on this module, then mappings between each bridge and the ports it used would be appropriate.
Also, in the case of a single backplane repeater, a mapping
McCloghrie & Bierman Standards Track [Page 18]
RFC 2037 Entity MIB using SMIv2 October 1996
for the backplane to the single repeater entity is not necessary." ::= { entityMapping 1 }
entLPMappingEntry OBJECT-TYPE SYNTAX EntLPMappingEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "Information about a particular logical entity to physical equipment association. Note that the nature of the association is not specifically identified in this entry. It is expected that sufficient information exists in the MIBs used to manage a particular logical entity to infer how physical component information is utilized." INDEX { entLogicalIndex, entLPPhysicalIndex } ::= { entLPMappingTable 1 }
entLPPhysicalIndex OBJECT-TYPE SYNTAX PhysicalIndex MAX-ACCESS read-only STATUS current DESCRIPTION "The value of this object identifies the index value of a particular entPhysicalEntry associated with the indicated entLogicalEntity." ::= { entLPMappingEntry 1 }
-- logical entity/component to alias table entAliasMappingTable OBJECT-TYPE SYNTAX SEQUENCE OF EntAliasMappingEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "This table contains zero or more rows, representing mappings of logical entity and physical component to external MIB identifiers. Each physical port in the system may be associated with a mapping to an external identifier, which itself is associated with a particular logical entity's naming scope. A 'wildcard' mechanism is provided to indicate that an identifier is associated with more than one logical entity." ::= { entityMapping 2 }
McCloghrie & Bierman Standards Track [Page 19]
RFC 2037 Entity MIB using SMIv2 October 1996
entAliasMappingEntry OBJECT-TYPE SYNTAX EntAliasMappingEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "Information about a particular physical equipment, logical entity to external identifier binding. Each logical entity/physical component pair may be associated with one alias mapping. The logical entity index may also be used as a 'wildcard' (refer to the entAliasLogicalIndexOrZero object DESCRIPTION clause for details.)
Note that only entPhysicalIndex values which represent physical ports (i.e. associated entPhysicalClass value is 'port(10)') are permitted to exist in this table." INDEX { entPhysicalIndex, entAliasLogicalIndexOrZero } ::= { entAliasMappingTable 1 }
entAliasLogicalIndexOrZero OBJECT-TYPE SYNTAX INTEGER (0..2147483647) MAX-ACCESS not-accessible STATUS current DESCRIPTION "The value of this object uniquely identifies the logical entity which defines the naming scope for the associated instance of the 'entAliasMappingIdentifier' object.
If this object has a non-zero value, then it identifies the logical entity named by the same value of entLogicalIndex.
If this object has a value of zero, then the mapping between the physical component and the alias identifier for this entAliasMapping entry is associated with all unspecified logical entities. That is, a value of zero (the default mapping) identifies any logical entity which does not have an explicit entry in this table for a particular entPhysicalIndex/entAliasMappingIdentifier pair.
For example, to indicate that a particular interface (e.g. physical component 33) is identified by the same value of ifIndex for all logical entities, the following instance might exist:
McCloghrie & Bierman Standards Track [Page 20]
RFC 2037 Entity MIB using SMIv2 October 1996
entAliasMappingIdentifier.33.0 = ifIndex.5
In the event an entPhysicalEntry is associated differently for some logical entities, additional entAliasMapping entries may exist, e.g.:
Note that entries with non-zero entAliasLogicalIndexOrZero index values have precedence over any zero-indexed entry. In this example, all logical entities except 4, 5, and 10, associate physical entity 33 with ifIndex.6." ::= { entAliasMappingEntry 1 }
entAliasMappingIdentifier OBJECT-TYPE SYNTAX RowPointer MAX-ACCESS read-only STATUS current DESCRIPTION "The value of this object identifies a particular conceptual row associated with the indicated entPhysicalIndex and entLogicalIndex pair.
Since only physical ports are modeled in this table, only entries which represent interfaces or ports are allowed. If an ifEntry exists on behalf of a particular physical port, then this object should identify the associated 'ifEntry'. For repeater ports, the appropriate row in the 'rptrPortGroupTable' should be identified instead.
For example, suppose a physical port was represented by entPhysicalEntry.3, entLogicalEntry.15 existed for a repeater, and entLogicalEntry.22 existed for a bridge. Then there might be two related instances of entAliasMappingIdentifier: entAliasMappingIdentifier.3.15 == rptrPortGroupIndex.5.2 entAliasMappingIdentifier.3.22 == ifIndex.17 It is possible that other mappings (besides interfaces and repeater ports) may be defined in the future, as required.
Bridge ports are identified by examining the Bridge MIB and appropriate ifEntries associated with each 'dot1dBasePort', and are thus not represented in this table." ::= { entAliasMappingEntry 2 }
McCloghrie & Bierman Standards Track [Page 21]
RFC 2037 Entity MIB using SMIv2 October 1996
-- physical mapping table entPhysicalContainsTable OBJECT-TYPE SYNTAX SEQUENCE OF EntPhysicalContainsEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "A table which exposes the container/containee relationships between physical entities. This table provides equivalent information found by constructing the virtual containment tree for a given entPhysicalTable but in a more direct format." ::= { entityMapping 3 }
entPhysicalContainsEntry OBJECT-TYPE SYNTAX EntPhysicalContainsEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "A single container/containee relationship." INDEX { entPhysicalIndex, entPhysicalChildIndex } ::= { entPhysicalContainsTable 1 }
entPhysicalChildIndex OBJECT-TYPE SYNTAX PhysicalIndex MAX-ACCESS read-only STATUS current DESCRIPTION "The value of entPhysicalIndex for the contained physical entity." ::= { entPhysicalContainsEntry 1 }
-- last change time stamp for the whole MIB entLastChangeTime OBJECT-TYPE SYNTAX TimeStamp MAX-ACCESS read-only STATUS current DESCRIPTION "The value of sysUpTime at the time any of these events occur: * a conceptual row is created or deleted in any of these tables: - entPhysicalTable - entLogicalTable - entLPMappingTable
McCloghrie & Bierman Standards Track [Page 22]
RFC 2037 Entity MIB using SMIv2 October 1996
- entAliasMappingTable - entPhysicalContainsTable
* any instance in the following list of objects changes value: - entPhysicalDescr - entPhysicalVendorType - entPhysicalContainedIn - entPhysicalClass - entPhysicalParentRelPos - entPhysicalName - entLogicalDescr - entLogicalType - entLogicalCommunity - entLogicalTAddress - entLogicalTDomain - entAliasMappingIdentifier " ::= { entityGeneral 1 }
entConfigChange NOTIFICATION-TYPE STATUS current DESCRIPTION "An entConfigChange trap is sent when the value of entLastChangeTime changes. It can be utilized by an NMS to trigger logical/physical entity table maintenance polls.
An agent must not generate more than one entConfigChange 'trap-event' in a five second period, where a 'trap-event' is the transmission of a single trap PDU to a list of trap destinations. If additional configuration changes occur within the five second 'throttling' period, then these trap-events should be suppressed by the agent. An NMS should periodically check the value of entLastChangeTime to detect any missed entConfigChange trap-events, e.g. due to throttling or transmission loss." ::= { entityMIBTrapPrefix 1 }
entityCompliance MODULE-COMPLIANCE STATUS current DESCRIPTION "The compliance statement for SNMP entities which implement the Entity MIB." MODULE -- this module MANDATORY-GROUPS { entityPhysicalGroup, entityLogicalGroup, entityMappingGroup, entityGeneralGroup, entityNotificationsGroup } ::= { entityCompliances 1 }
-- MIB groupings
entityPhysicalGroup OBJECT-GROUP OBJECTS { entPhysicalDescr, entPhysicalVendorType, entPhysicalContainedIn, entPhysicalClass, entPhysicalParentRelPos, entPhysicalName } STATUS current DESCRIPTION "The collection of objects which are used to represent physical system components, for which a single agent provides management information." ::= { entityGroups 1 }
entityLogicalGroup OBJECT-GROUP OBJECTS { entLogicalDescr, entLogicalType, entLogicalCommunity, entLogicalTAddress, entLogicalTDomain } STATUS current DESCRIPTION "The collection of objects which are used to represent the list of logical entities for which a single agent provides management information." ::= { entityGroups 2 }
entityMappingGroup OBJECT-GROUP OBJECTS {
McCloghrie & Bierman Standards Track [Page 24]
RFC 2037 Entity MIB using SMIv2 October 1996
entLPPhysicalIndex, entAliasMappingIdentifier, entPhysicalChildIndex } STATUS current DESCRIPTION "The collection of objects which are used to represent the associations between multiple logical entities, physical components, interfaces, and port identifiers for which a single agent provides management information." ::= { entityGroups 3 }
entityGeneralGroup OBJECT-GROUP OBJECTS { entLastChangeTime } STATUS current DESCRIPTION "The collection of objects which are used to represent general entity information for which a single agent provides management information." ::= { entityGroups 4 }
entityNotificationsGroup NOTIFICATION-GROUP NOTIFICATIONS { entConfigChange } STATUS current DESCRIPTION "The collection of notifications used to indicate Entity MIB data consistency and general status information." ::= { entityGroups 5 }
The following sections iterate the instance values for two example networking devices. These examples are kept simple to make them more understandable. Auxiliary components, such as fans, sensors, empty slots, and sub-modules are not shown, but might be modeled in real implementations.
A router containing two slots. Each slot contains a 3 port router/bridge module. Each port is represented in the ifTable. There are two logical instances of OSPF running and two logical bridges:
[ed. -- Note that these mappings are included in the table since another logical entity (1st OSPF) utilizes one of the ports. If this were not the case, then a single mapping to the module (e.g. entLPPhysicalIndex.3.4) would be present instead. ] entLPPhysicalIndex.3.5 == 5 entLPPhysicalIndex.3.6 == 6 entLPPhysicalIndex.3.7 == 7
Physical to Logical to MIB Alias Mappings -- entAliasMappingTable: Example 1: ifIndex values are global to all logical entities entAliasMappingIdentifier.5.0 == ifIndex.1 entAliasMappingIdentifier.6.0 == ifIndex.2 entAliasMappingIdentifier.7.0 == ifIndex.3 entAliasMappingIdentifier.9.0 == ifIndex.4 entAliasMappingIdentifier.10.0 == ifIndex.5 entAliasMappingIdentifier.11.0 == ifIndex.6
Example 2: ifIndex values are not shared by all logical entities entAliasMappingIdentifier.5.0 == ifIndex.1 entAliasMappingIdentifier.5.3 == ifIndex.101 entAliasMappingIdentifier.6.0 == ifIndex.2 entAliasMappingIdentifier.6.3 == ifIndex.102 entAliasMappingIdentifier.7.0 == ifIndex.3 entAliasMappingIdentifier.7.3 == ifIndex.103 entAliasMappingIdentifier.9.0 == ifIndex.4 entAliasMappingIdentifier.9.3 == ifIndex.204 entAliasMappingIdentifier.10.0 == ifIndex.5 entAliasMappingIdentifier.10.3 == ifIndex.205 entAliasMappingIdentifier.11.0 == ifIndex.6 entAliasMappingIdentifier.11.3 == ifIndex.206
Physical Containment Tree -- entPhysicalContainsTable chassis has two containers: entPhysicalChildIndex.1.2 = 2 entPhysicalChildIndex.1.3 = 3
container 1 has a module: entPhysicalChildIndex.2.4 = 4
container 2 has a module: entPhysicalChildIndex.3.8 = 8
A 3-slot Hub with 2 backplane ethernet segments. Slot three is empty, and the remaining slots contain ethernet repeater modules. [ed. -- Note that a replacement for the current Repeater MIB (RFC 1516) is likely to emerge soon, and it will no longer be necessary to access repeater MIB data in different naming scopes.]
Logical entities -- entLogicalTable Repeater 1--comprised of any ports attached to backplane 1 entLogicalDescr.1 == "Acme repeater v3.1" entLogicalType.1 == snmpDot3RptrMgt entLogicalCommunity.1 "public-repeater1" entLogicalTAddress.1 == 124.125.126.127:161 entLogicalTDomain.1 == snmpUDPDomain
Repeater 2--comprised of any ports attached to backplane 2: entLogicalDescr.2 == "Acme repeater v3.1" entLogicalType.2 == snmpDot3RptrMgt entLogicalCommunity.2 == "public-repeater2" entLogicalTAddress.2 == 124.125.126.127:161 entLogicalTDomain.2 == snmpUDPDomain
Logical to Physical Mappings -- entLPMappingTable:
repeater1 uses backplane 1, slot 1-ports 1 & 2, slot 2-port 1 [ed. -- Note that a mapping to the module is not included, since in this example represents a port-switchable hub. Even though all ports on the module could belong to the same repeater as a matter of configuration, the LP port mappings should not be replaced dynamically with a single mapping for the module (e.g. entLPPhysicalIndex.1.7). If all ports on the module shared a single backplane connection, then a single mapping for the module would be more appropriate. ]
[1] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Structure of Management Information for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1902, January 1996.
[2] McCloghrie, K., and M. Rose, Editors, "Management Information Base for Network Management of TCP/IP-based internets: MIB-II", STD 17, RFC 1213, Hughes LAN Systems, Performance Systems International, March 1991.
[3] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Textual Conventions for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1903, January 1996.
[4] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Protocol Operations for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1905, January 1996.
[5] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Conformance Statements for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1904, January 1996.
[6] Case, J., M. Fedor, M. Schoffstall, J. Davin, "Simple Network Management Protocol", RFC 1157, SNMP Research, Performance Systems International, MIT Laboratory for Computer Science, May 1990.
[7] McCloghrie, K., and Kastenholtz, F., "Interfaces Group Evolution", RFC 1573, Hughes LAN Systems, FTP Software, January 1994.
[8] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Transport Mappings for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1906, January 1996.
[9] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Introduction to Community-based SNMPv2", RFC 1901, January 1996.
In order to implement this MIB, an agent must make certain management information available about various logical and physical entities within a managed system, which may be considered sensitive in some network environments.
Therefore, a network administrator may wish to employ instance-level access control, and configure the Entity MIB access (i.e., community strings in SNMPv1 and SNMPv2C), such that certain instances within this MIB (e.g., entLogicalCommunity, or entire entLogicalEntries, entPhysicalEntries, and associated mapping table entries), are excluded from particular MIB views.