Network Working Group M. Rose, Editor
Request for Comments: 1158 Performance Systems International
May 1990
Management Information Base for Network Management
of TCP/IP-based internets:
MIB-II
1. Status of this Memo
This memo defines the second version of the Management Information
Base (MIB-II) for use with network management protocols in TCP/IP-
based internets. In particular, together with its companion memos
which describe the structure of management information (RFC1155)
along with the network management protocol (RFC1157) for TCP/IP-
based internets, these documents provide a simple, workable
architecture and system for managing TCP/IP-based internets and in
particular the Internet community.
This document on MIB-II incorporates all of the technical content of
RFC1156 on MIB-I and extends it, without loss of compatibilty.
However, MIB-I as described in RFC1156 is full Standard Protocol of
the Internet, while the MIB-II described here is Proposed Standard
Protocol of the Internet.
This memo defines a mandatory extension to the base MIB (RFC1156)
and is a Proposed Standard for the Internet community. The
extensions described here are currently Elective, but when they
become a standard, they will have the same status as RFC1156, that
is, Recommended. The Internet Activities Board recommends that all
IP and TCP implementations be network manageable. This implies
implementation of the Internet MIB (RFC1156 and the extensions in
RFC1158) and at least one of the two recommended management
protocols SNMP (RFC1157) or CMOT (RFC1095).
This version of the MIB specification, MIB-II, is an incremental
refinement of MIB-I. As such, it has been designed according to two
criteria: first, changes have been made in response to new
operational requirements in the Internet; and, second, the changes
are entirely upwards compatible in order to minimize impact on the
network as the managed nodes in the Internet transition from MIB-I to
MIB-II.
It is expected that additional MIB groups and variables will be
defined over time to accommodate the monitoring and control needs of
new or changing components of the Internet.
Please refer to the latest edition of the "IAB Official Protocol
Standards" RFCfor current information on the state and status of
standard Internet protocols.
Distribution of this memo is unlimited.
Table of Contents
1. Status of this Memo .................................. 1
2. Introduction ......................................... 3
3. Changes from MIB-I ................................... 4
3.1 Deprecated Objects .................................. 4
3.2 Display Strings ..................................... 5
3.3 The System Group .................................... 5
3.4 The Interfaces Group ................................ 5
3.5 The Address Translation Group ....................... 6
3.6 The IP Group ........................................ 7
3.7 The ICMP Group ...................................... 7
3.8 The TCP Group ....................................... 7
3.9 The UDP Group ....................................... 7
3.10 The EGP Group ...................................... 8
3.11 The Transmission Group ............................. 8
3.12 The SNMP Group ..................................... 8
4. Objects .............................................. 8
4.1 Object Groups ....................................... 9
4.2 Format of Definitions ............................... 10
5. Object Definitions ................................... 10
5.1 The System Group .................................... 11
5.2 The Interfaces Group ................................ 14
5.2.1 The Interfaces table .............................. 15
5.3 The Address Translation Group ....................... 27
5.4 The IP Group ........................................ 30
5.4.1 The IP Address table .............................. 38
5.4.2 The IP Routing table .............................. 41
5.4.3 The IP Address Translation table .................. 48
5.5 The ICMP Group ...................................... 51
5.6 The TCP Group ....................................... 61
5.6.1 The TCP Connection table .......................... 66
5.6.2 Additional TCP Objects ............................ 69
5.7 The UDP Group ....................................... 70
5.7.1 The UDP Listener table ............................ 72
5.8 The EGP Group ....................................... 73
5.8.1 The EGP Neighbor table ............................ 75
5.8.2 Additional EGP variables .......................... 83
5.9 The Transmission Group .............................. 83
5.10 The SNMP Group ..................................... 83
6. Definitions .......................................... 95
7. Identification of OBJECT instances for use with the
SNMP ................................................. 126
7.1 ifTable Object Type Names ........................... 127
7.2 atTable Object Type Names ........................... 127
7.3 ipAddrTable Object Type Names ....................... 128
7.4 ipRoutingTable Object Type Names .................... 128
7.5 ipNetToMediaTable Object Type Names ................. 129
7.6 tcpConnTable Object Type Names ...................... 129
7.7 udpTable Object Type Names .......................... 130
7.8 egpNeighTable Object Type Names ..................... 130
8. Acknowledgements .................................... 130
9. References .......................................... 131
10. Security Considerations.............................. 133
11. Author's Address..................................... 133
2. Introduction
As reported in RFC1052, IAB Recommendations for the
Development of Internet Network Management Standards [1], a
two-prong strategy for network management of TCP/IP-based
internets was undertaken. In the short-term, the Simple
Network Management Protocol (SNMP) was to be used to manage
nodes in the Internet community. In the long-term, the use of
the OSI network management framework was to be examined. Two
documents were produced to define the management information:
RFC1065, which defined the Structure of Management
Information (SMI) [2], and RFC1066, which defined the
Management Information Base (MIB) [3]. Both of these
documents were designed so as to be compatible with both the
SNMP and the OSI network management framework.
This strategy was quite successful in the short-term:
Internet-based network management technology was fielded, by
both the research and commercial communities, within a few
months. As a result of this, portions of the Internet
community became network manageable in a timely fashion.
As reported in RFC1109, Report of the Second Ad Hoc Network
Management Review Group [4], the requirements of the SNMP and
the OSI network management frameworks were more different than
anticipated. As such, the requirement for compatibility
between the SMI/MIB and both frameworks was suspended. This
action permitted the operational network management framework,
the SNMP, to respond to new operational needs in the Internet
community by producing this document.
As such, the current network management framework for TCP/IP-
based internets consists of: Structure and Identification of
Management Information for TCP/IP-based internets, RFC1155 [13],
which describes how managed objects contained in the MIB are
defined; Management Information Base for Network Management of
TCP/IP-based internets (version 2), this memo, which describes
the managed objects contained in the MIB; and, the Simple
Network Management Protocol, RFC1157 [14], which defines the
protocol used to manage these objects.
Consistent with the IAB directive to produce simple, workable
systems in the short-term, the list ofc objects (e.g., for BSD UNIX)
were excluded.
7) It was agreed to avoid heavily instrumenting critical
sections of code. The general guideline was one counter
per critical section per layer.
3. Changes from MIB-I
Features of this MIB include:
1) incremental additions to reflect new operational
requirements;
2) upwards compatibility with the SMI/MIB and the SNMP;
3) improved support for multi-protocol entities; and,
4) textual clean-up of the MIB to improve clarity and
readability.
The objects defined in MIB-II have the OBJECT IDENTIFIER prefix:
mib-2 OBJECT IDENTIFIER ::= { mgmt 1 }
3.1. Deprecated Objects
In order to better prepare implementors for future changes in the
MIB, a new term "deprecated" may be used when describing an object.
A deprecated object in the MIB is one which must be supported, but
one which will most likely be removed from the next version of the
MIB (e.g., MIB-III).
MIB-II marks one object as being deprecated:
atTable
As a result of deprecating the atTable object, the entire Address
Translation group is deprecated.
Note that no functionality is lost with the deprecation of these
objects: new objects providing equivalent or superior functionality
are defined in MIB-II.
3.2. Display Strings
In the past, there have been misinterpretations of the MIB as to when
a string of octets should contain printable characters, meant to be
displayed to a human. As a textual convention in the MIB, the
datatype
DisplayString ::= OCTET STRING
is introduced. A DisplayString is restricted to the NVT ASCII
character set, as defined in pages 10-11 of [7].
The following objects are now defined in terms of DisplayString:
sysDescr
ifDescr
It should be noted that this change has no effect on either the
syntax nor semantics of these objects. The use of the DisplayString
notation is merely an artifact of the explanatory method used in
MIB-II and future MIBs.
Further, it should be noted that any object defined in terms of OCTET
STRING may contain arbitrary binary data, in which each octet may
take any value from 0 to 255 (decimal).
3.3. The System Group
Four new objects are added to this group:
sysContact
sysName
sysLocation
sysServices
These provide contact, administrative, location, and service
information regarding the managed node.
3.4. The Interfaces Group
The definition of the ifNumber object was incorrect, as it required
all interfaces to support IP. (For example, devices without IP, such
as MAC-layer bridges, could not be managed if this definition was
strictly followed.) The description of the ifNumber object is changed
accordingly.
The ifTable object was mistaken marked as read-write, it has been
(correctly) re-designated as read-only. In addition, several new
values have been added to the ifType column in the ifTable object:
ppp(23)
softwareLoopback(24)
eon(25)
ethernet-3Mbit(26)
nsip(27)
slip(28)
Finally, a new column has been added to the ifTable object:
ifSpecific
which provides information about information specific to the media
being used to realize the interface.
3.5. The Address Translation Group
In MIB-I, this group contained a table which permitted mappings from
network addresses (e.g., IP addresses) to physical addresses (e.g.,
MAC addresses). Experience has shown that efficient implementations
of this table make two assumptions: a single network protocol
environment, and mappings occur only from network address to physical
address.
The need to support multi-protocol nodes (e.g., those with both the
IP and CLNP active), and the need to support the inverse mapping
(e.g., for ES-IS), have invalidated both of these assumptions. As
such, the atTable object is declared deprecated.
In order to meet both the multi-protocol and inverse mapping
requirements, MIB-II and its successors will allocate up to two
address translation tables inside each network protocol group. That
is, the IP group will contain one address translation table, for
going from IP addresses to physical addresses. Similarly, when a
document defining MIB objects for the CLNP is produced (e.g., [8]),
it will contain two tables, for mappings in both directions, as this
is required for full functionality.
It should be noted that the choice of two tables (one for each
direction of mapping) provides for ease of implementation in many
cases, and does not introduce undue burden on implementations which
realize the address translation abstraction through a single internal
table.
3.6. The IP Group
The access attribute of the variable ipForwarding has been changed
from read-only to read-write.
In addition, there is a new column to the ipAddrTable object,
ipAdEntReasmMaxSize
which keeps track of the largest IP datagram that can be re-
assembled on a particular interface. There is also a new column in
the ipRoutingTable object,
ipRouteMask
which is used for IP routing subsystems that support arbitrary subnet
masks.
One new object is added to the IP group:
ipNetToMediaTable
which is the address translation table for the IP group (providing
identical functionality to the now deprecated atTable in the address
translation group).
3.7. The ICMP Group
There are no changes to this group.
3.8. The TCP Group
Two new variables are added:
tcpInErrs
tcpOutRsts
which keep track of the number of incoming TCP segments in error and
the number of resets generated by a TCP.
3.9. The UDP Group
A new table:
udpTable
is added.
3.10. The EGP Group
Experience has indicated a need for additional objects that are
useful in EGP monitoring. In addition to making several additions to
the egpNeighborTable object, a new variable is added:
egpAs
which gives the autonomous system associated with this EGP entity.
3.11. The Transmission Group
MIB-I was lacking in that it did not distinguish between different
types of transmission media. A new group, the Transmission group, is
allocated for this purpose:
transmission OBJECT IDENTIFIER ::= { mib-2 10 }
When Internet-standard definitions for managing transmission media
are defined, the transmission group is used to provide a prefix for
the names of those objects.
Typically, such definitions reside in the experimental portion of the
MIB until they are "proven", then as a part of the Internet
standardization process, the definitions are accordingly elevated and
a new object identifier, under the transmission group is defined. By
convention, the name assigned is:
type OBJECT IDENTIFIER ::= { transmission number }
where "type" is the symbolic value used for the media in the ifType
column of the ifTable object, and "number" is the actual integer
value corresponding to the symbol.
3.12. The SNMP Group
The application-oriented working groups of the IETF have been tasked
to be receptive towards defining MIB variables specific to their
respective applications.
For the SNMP, it is useful to have statistical information. A new
group, the SNMP group, is allocated for this purpose:
snmp OBJECT IDENTIFIER ::= { mib-2 11 }
4. Objects
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. Objects in the MIB are
defined using Abstract Syntax Notation One (ASN.1) [9].
The mechanisms used for describing these objects are specified the
companion memo, the SMI. In particular, each object has a name, a
syntax, and an encoding. The name is an object identifier, an
administratively assigned name, which specifies an object type. 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 OBJECT
DESCRIPTOR, to also refer to the object type.
The syntax of an object type defines the abstract data structure
corresponding to that object type. The ASN.1 language is used for
this purpose. However, the companion memo purposely restricts the
ASN.1 constructs which may be used. These restrictions are
explicitly made for simplicity.
The encoding of an object type is simply how that object type is
represented using the object type's syntax. Implicitly tied to the
notion of an object type's syntax and encoding is how the object type
is represented when being transmitted on the network. This memo
specifies the use of the basic encoding rules (BER) of ASN.1 [10],
subject to the additional requirements imposed by the SNMP [14].
4.1. Object Groups
Since this list of managed objects contains only the essential
elements, there is no need to allow individual objects to be
optional. Rather, the objects are arranged into the following
groups:
- System
- Interfaces
- Address Translation (deprecated)
- IP
- ICMP
- TCP
- UDP
- EGP
- Transmission
- SNMP
There are two reasons for defining these groups: to provide a means
of assigning object identifiers; and, to provide a method for
implementations of managed agents to know which objects they must
implement. This method is as follows: if the semantics of a group is
applicable to an implementation, then it must implement all objects
in that group. For example, an implementation must implement the EGP
group if and only if it implements the EGP.
4.2. Format of Definitions
The next section contains the specification of all object types
contained in the MIB. Following the conventions of the companion
memo, the object types are defined using the following fields:
OBJECT:
-------
A textual name, termed the OBJECT DESCRIPTOR, for the
object type, along with its corresponding OBJECT
IDENTIFIER.
Syntax:
The abstract syntax for the object type, presented using
ASN.1. This must resolve to an instance of the ASN.1
type ObjectSyntax defined in the SMI.
Definition:
A textual description of the semantics of the object
type. Implementations should ensure that their
interpretation of the object type fulfills this
definition since this MIB is intended for use in multi-
vendor environments. As such it is vital that object
types have consistent meaning across all machines.
Access:
A keyword, one of read-only, read-write, write-only, or
not-accessible. Note that this designation specifies the
minimum level of support required. As a local matter,
implementations may support other access types (e.g., an
implementation may elect to permitting writing a variable
marked herein as read-only). Further, protocol-specific
"views" (e.g., those implied by an SNMP community) may
make further restrictions on access to a variable.
Status:
A keyword, one of mandatory, optional, obsolete, or
deprecated. Use of deprecated implies mandatory status.
5. Object Definitions
RFC1158-MIB
DEFINITIONS ::= BEGIN
IMPORTS
mgmt, OBJECT-TYPE, NetworkAddress, IpAddress,
Counter, Gauge, TimeTicks
FROM RFC1155-SMI;
DisplayString ::=
OCTET STRING
mib-2 OBJECT IDENTIFIER ::= { mgmt 1 } -- MIB-II
system OBJECT IDENTIFIER ::= { mib-2 1 }
interfaces OBJECT IDENTIFIER ::= { mib-2 2 }
at OBJECT IDENTIFIER ::= { mib-2 3 }
ip OBJECT IDENTIFIER ::= { mib-2 4 }
icmp OBJECT IDENTIFIER ::= { mib-2 5 }
tcp OBJECT IDENTIFIER ::= { mib-2 6 }
udp OBJECT IDENTIFIER ::= { mib-2 7 }
egp OBJECT IDENTIFIER ::= { mib-2 8 }
-- cmot OBJECT IDENTIFIER ::= { mib-2 9 }
transmission OBJECT IDENTIFIER ::= { mib-2 10 }
snmp OBJECT IDENTIFIER ::= { mib-2 11 }
END
5.1. The System Group
Implementation of the System group is mandatory for all systems.
OBJECT:
-------
sysDescr { system 1 }
Syntax:
DisplayString (SIZE (0..255))
Definition:
A textual description of the entity. This value should
include the full name and version identification of the
system's hardware type, software operating-system, and
networking software. It is mandatory that this only
contain printable ASCII characters.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
sysObjectID { system 2 }
Syntax:
OBJECT IDENTIFIER
Definition:
The vendor's authoritative identification of the network
management subsystem contained in the entity. This value
is allocated within the SMI enterprises subtree
(1.3.6.1.4.1) and provides an easy and unambiguous means
for determining "what kind of box" is being managed. For
example, if vendor "Flintstones, Inc." was assigned the
subtree 1.3.6.1.4.1.4242, it could assign the identifier
1.3.6.1.4.1.4242.1.1 to its "Fred Router".
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
sysUpTime { system 3 }
Syntax:
TimeTicks
Definition:
The time (in hundredths of a second) since the network
management portion of the system was last re-initialized.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
sysContact { system 4 }
Syntax:
DisplayString (SIZE (0..255))
Definition:
The textual identification of the contact person for this
managed node, together with information on how to contact
this person.
Access:
read-write.
Status:
mandatory.
OBJECT:
-------
sysName { system 5 }
Syntax:
DisplayString (SIZE (0..255))
Definition:
An administratively-assigned name for this managed node.
By convention, this is the node's fully-qualified domain
name.
Access:
read-write.
Status:
mandatory.
OBJECT:
-------
sysLocation { system 6 }
Syntax:
DisplayString (SIZE (0..255))
Definition:
The physical location of this node (e.g., "telephone
closet, 3rd floor").
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
sysServices { system 7 }
Syntax:
INTEGER (0..127)
Definition:
A value which indicates the set of services that this
entity potentially offers. The value is a sum. This
sum initially takes the value zero, Then, for each layer,
L, in the range 1 through 7, that this node performs
transactions for, 2 raised to (L - 1) is added to the
sum. For example, a node which performs only routing
functions would have a value of 4 (2^(3-1)). In
contrast, a node which is a host offering application
services would have a value of 72 (2^(4-1) + 2^(7-1)).
Note that in the context of the Internet suite of
protocols, values should be calculated accordingly:
layer functionality
1 physical (e.g., repeaters)
2 datalink/subnetwork (e.g., bridges)
3 internet (e.g., supports the IP)
4 end-to-end (e.g., supports the TCP)
7 applications (e.g., supports the SMTP)
For systems including OSI protocols, layers 5 and 6 may
also be counted.
Access:
read-only.
Status:
mandatory.
5.2. The Interfaces Group
Implementation of the Interfaces group is mandatory for all systems.
OBJECT:
-------
ifNumber { interfaces 1 }
Syntax:
INTEGER
Definition:
The number of network interfaces (regardless of their
current state) present on this system.
Access:
read-only.
Status:
mandatory.
5.2.1. The Interfaces table
The Interfaces table contains information on the entity's interfaces.
Each interface is thought of as being attached to a "subnetwork".
Note that this term should not be confused with "subnet" which refers
to an addressing partitioning scheme used in the Internet suite of
protocols.
OBJECT:
-------
ifTable { interfaces 2 }
Syntax:
SEQUENCE OF IfEntry
Definition:
A list of interface entries. The number of entries is
given by the value of ifNumber.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifEntry { ifTable 1 }
Syntax:
IfEntry ::= SEQUENCE {
ifIndex
INTEGER,
ifDescr
DisplayString,
ifType
INTEGER,
ifMtu
INTEGER,
ifSpeed
Gauge,
ifPhysAddress
OCTET STRING,
ifAdminStatus
INTEGER,
ifOperStatus
INTEGER,
ifLastChange
TimeTicks,
ifInOctets
Counter,
ifInUcastPkts
Counter,
ifInNUcastPkts
Counter,
ifInDiscards
Counter,
ifInErrors
Counter,
ifInUnknownProtos
Counter,
ifOutOctets
Counter,
ifOutUcastPkts
Counter,
ifOutNUcastPkts
Counter,
ifOutDiscards
Counter,
ifOutErrors
Counter,
ifOutQLen
Gauge,
ifSpecific
OBJECT IDENTIFIER
}
Definition:
An interface entry containing objects at the subnetwork
layer and below for a particular interface.
Access:
read-only.
Status:
mandatory.
We now consider the individual components of each interface
entry:
OBJECT:
-------
ifIndex { ifEntry 1 }
Syntax:
INTEGER
Definition:
A unique value for each interface. Its value ranges
between 1 and the value of ifNumber. The value for each
interface must remain constant at least from one re-
initialization of the entity's network management system
to the next re-initialization.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifDescr { ifEntry 2 }
Syntax:
DisplayString (SIZE (0..255))
Definition:
A textual string containing information about the
interface. This string should include the name of the
manufacturer, the product name and the version of the
hardware interface.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifType { ifEntry 3 }
Syntax:
INTEGER {
other(1), -- none of the following
regular1822(2),
hdh1822(3),
ddn-x25(4),
rfc877-x25(5),
ethernet-csmacd(6),
iso88023-csmacd(7),
iso88024-tokenBus(8),
iso88025-tokenRing(9),
iso88026-man(10),
starLan(11),
proteon-10Mbit(12),
proteon-80Mbit(13),
hyperchannel(14),
fddi(15),
lapb(16),
sdlc(17),
t1-carrier(18),
cept(19), -- european equivalent of T-1
basicISDN(20),
primaryISDN(21),
-- proprietary serial
propPointToPointSerial(22),
ppp(23),
softwareLoopback(24),
eon(25), -- CLNP over IP [12]
ethernet-3Mbit(26)
nsip(27), -- XNS over IP
slip(28) -- generic SLIP
}
Definition:
The type of interface, distinguished according to the
physical/link protocol(s) immediately "below" the network
layer in the protocol stack.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifMtu { ifEntry 4 }
Syntax:
INTEGER
Definition:
The size of the largest datagram which can be
sent/received on the interface, specified in octets. For
interfaces that are used for transmitting network
datagrams, this is the size of the largest network
datagram that can be sent on the interface.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifSpeed { ifEntry 5 }
Syntax:
Gauge
Definition:
An estimate of the interface's current bandwidth in bits
per second. For interfaces which do not vary in
bandwidth or for those where no accurate estimation can
be made, this object should contain the nominal
bandwidth.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifPhysAddress { ifEntry 6 }
Syntax:
OCTET STRING
Definition:
The interface's address at the protocol layer immediately
"below" the network layer in the protocol stack. For
interfaces which do not have such an address (e.g., a
serial line), this object should contain an octet string
of zero length.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifAdminStatus { ifEntry 7 }
Syntax:
INTEGER {
up(1), -- ready to pass packets
down(2),
testing(3) -- in some test mode
}
Definition:
The desired state of the interface. The testing(3) state
indicates that no operational packets can be passed.
Access:
read-write.
Status:
mandatory.
OBJECT:
-------
ifOperStatus { ifEntry 8 }
Syntax:
INTEGER {
up(1), -- ready to pass packets
down(2),
testing(3) -- in some test mode
}
Definition:
The current operational state of the interface. The
testing(3) state indicates that no operational packets
can be passed.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifLastChange { ifEntry 9 }
Syntax:
TimeTicks
Definition:
The value of sysUpTime at the time the interface entered
its current operational state. If the current state was
entered prior to the last re-initialization of the local
network management subsystem, then this object contains a
zero value.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifInOctets { ifEntry 10 }
Syntax:
Counter
Definition:
The total number of octets received on the interface,
including framing characters.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifInUcastPkts { ifEntry 11 }
Syntax:
Counter
Definition:
The number of subnetwork-unicast packets delivered to a
higher-layer protocol.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifInNUcastPkts { ifEntry 12 }
Syntax:
Counter
Definition:
The number of non-unicast (i.e., subnetwork-broadcast or
subnetwork-multicast) packets delivered to a higher-layer
protocol.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifInDiscards { ifEntry 13 }
Syntax:
Counter
Definition:
The number of inbound packets which were chosen to be
discarded even though no errors had been detected to
prevent their being deliverable to a higher-layer
protocol. One possible reason for discarding such a
packet could be to free up buffer space.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifInErrors { ifEntry 14 }
Syntax:
Counter
Definition:
The number of inbound packets that contained errors
preventing them from being deliverable to a higher-layer
protocol.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifInUnknownProtos { ifEntry 15 }
Syntax:
Counter
Definition:
The number of packets received via the interface which
were discarded because of an unknown or unsupported
protocol.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifOutOctets { ifEntry 16 }
Syntax:
Counter
Definition:
The total number of octets transmitted out of the
interface, including framing characters.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifOutUcastPkts { ifEntry 17 }
Syntax:
Counter
Definition:
The total number of packets that higher-level protocols
requested be transmitted to a subnetwork-unicast address,
including those that were discarded or not sent.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifOutNUcastPkts { ifEntry 18 }
Syntax:
Counter
Definition:
The total number of packets that higher-level protocols
requested be transmitted to a non-unicast (i.e., a
subnetwork-broadcast or subnetwork-multicast) address,
including those that were discarded or not sent.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifOutDiscards { ifEntry 19 }
Syntax:
Counter
Definition:
The number of outbound packets which were chosen to be
discarded even though no errors had been detected to
prevent their being transmitted. One possible reason for
discarding such a packet could be to free up buffer
space.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifOutErrors { ifEntry 20 }
Syntax:
Counter
Definition:
The number of outbound packets that could not be
transmitted because of errors.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifOutQLen { ifEntry 21 }
Syntax:
Gauge
Definition:
The length of the output packet queue (in packets).
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ifSpecific { ifEntry 22 }
Syntax:
OBJECT IDENTIFIER
Definition:
A reference to MIB definitions specific to the particular
media being used to realize the interface. For example,
if the interface is realized by an ethernet, then the
value of this object refers to a document defining
objects specific to ethernet. If an agent is not
configured to have a value for any of these variables,
the object identifier
nullSpecific OBJECT IDENTIFIER ::= { 0 0 }
is returned. Note that "nullSpecific" is a syntatically
valid object identifier, and any conformant
implementation of ASN.1 and BER must be able to generate
and recognize this value.
Access:
read-only.
Status:
mandatory.
5.3. The Address Translation Group
Implementation of the Address Translation group is mandatory for all
systems. Note however that this group is deprecated by MIB-II. That
is, it is being included solely for compatibility with MIB-I nodes,
and will most likely be excluded from MIB-III nodes. From MIB-II and
onwards, each network protocol group contains its own address
translation tables.
The Address Translation group contains one table which is the union
across all interfaces of the translation tables for converting a
NetworkAddress (e.g., an IP address) into a subnetwork-specific
address. For lack of a better term, this document refers to such a
subnetwork-specific address as a "physical" address.
Examples of such translation tables are: for broadcast media where
ARP is in use, the translation table is equivalent to the ARP cache;
or, on an X.25 network where non-algorithmic translation to X.121
addresses is required, the translation table contains the
NetworkAddress to X.121 address equivalences.
OBJECT:
-------
atTable { at 1 }
Syntax:
SEQUENCE OF AtEntry
Definition:
The Address Translation tables contain the NetworkAddress
to "physical" address equivalences. Some interfaces do
not use translation tables for determining address
equivalences (e.g., DDN-X.25 has an algorithmic method);
if all interfaces are of this type, then the Address
Translation table is empty, i.e., has zero entries.
Access:
read-write.
Status:
deprecated.
OBJECT:
-------
atEntry { atTable 1 }
Syntax:
AtEntry ::= SEQUENCE {
atIfIndex
INTEGER,
atPhysAddress
OCTET STRING,
atNetAddress
NetworkAddress
}
Definition:
Each entry contains one NetworkAddress to "physical"
address equivalence.
Access:
read-write.
Status:
deprecated.
We now consider the individual components of each Address
Translation table entry:
OBJECT:
-------
atIfIndex { atEntry 1 }
Syntax:
INTEGER
Definition:
The interface on which this entry's equivalence is
effective. The interface identified by a particular
value of this index is the same interface as identified
by the same value of ifIndex.
Access:
read-write.
Status:
deprecated.
OBJECT:
-------
atPhysAddress { atEntry 2 }
Syntax:
OCTET STRING
Definition:
The media-dependent "physical" address.
Setting this object to a null string (one of zero length) has
the effect of invaliding the corresponding entry in the
atTable object. That is, it effectively disassociates the
interface identified with said entry from the mapping
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 atPhysAddress object.
Access:
read-write.
Status:
deprecated.
OBJECT:
-------
atNetAddress { atEntry 3 }
Syntax:
NetworkAddress
Definition:
The NetworkAddress (e.g., the IP address) corresponding
to the media-dependent "physical" address.
Access:
read-write.
Status:
deprecated.
5.4. The IP Group
Implementation of the IP group is mandatory for all systems.
OBJECT:
-------
ipForwarding { ip 1 }
Syntax:
INTEGER {
forwarding(1), -- i.e., acting as a gateway
not-forwarding(2) -- i.e., NOT acting as a gateway
}
Definition:
The indication of whether this entity is acting as an IP
gateway in respect to the forwarding of datagrams
received by, but not addressed to, this entity. IP
gateways forward datagrams. IP hosts do not (except
those source-routed via the host).
Access:
read-write.
Status:
mandatory.
OBJECT:
-------
ipDefaultTTL { ip 2 }
Syntax:
INTEGER
Definition:
The default value inserted into the Time-To-Live field of
the IP header of datagrams originated at this entity,
whenever a TTL value is not supplied by the transport
layer protocol.
Access:
read-write.
Status:
mandatory.
OBJECT:
-------
ipInReceives { ip 3 }
Syntax:
Counter
Definition:
The total number of input datagrams received from
interfaces, including those received in error.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipInHdrErrors { ip 4 }
Syntax:
Counter
Definition:
The number of input datagrams discarded due to errors in
their IP headers, including bad checksums, version number
mismatch, other format errors, time-to-live exceeded,
errors discovered in processing their IP options, etc.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipInAddrErrors { ip 5 }
Syntax:
Counter
Definition:
The number of input datagrams discarded because the IP
address in their IP header's destination field was not a
valid address to be received at this entity. This count
includes invalid addresses (e.g., 0.0.0.0) and addresses
of unsupported Classes (e.g., Class E). For entities
which are not IP Gateways and therefore do not forward
datagrams, this counter includes datagrams discarded
because the destination address was not a local address.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipForwDatagrams { ip 6 }
Syntax:
Counter
Definition:
The number of input datagrams for which this entity was
not their final IP destination, as a result of which an
attempt was made to find a route to forward them to that
final destination. In entities which do not act as IP
Gateways, this counter will include only those packets
which were Source-Routed via this entity, and the
Source-Route option processing was successful.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipInUnknownProtos { ip 7 }
Syntax:
Counter
Definition:
The number of locally-addressed datagrams received
successfully but discarded because of an unknown or
unsupported protocol.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipInDiscards { ip 8 }
Syntax:
Counter
Definition:
The number of input IP datagrams for which no problems
were encountered to prevent their continued processing,
but which were discarded (e.g., for lack of buffer
space). Note that this counter does not include any
datagrams discarded while awaiting re-assembly.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipInDelivers { ip 9 }
Syntax:
Counter
Definition:
The total number of input datagrams successfully
delivered to IP user-protocols (including ICMP).
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipOutRequests { ip 10 }
Syntax:
Counter
Definition:
The total number of IP datagrams which local IP user-
protocols (including ICMP) supplied to IP in requests for
transmission. Note that this counter does not include
any datagrams counted in ipForwDatagrams.
Access:
read-only.
Status:
mandatory.
OBJECT:
ipOutDiscards { ip 11 }
Syntax:
Counter
Definition:
The number of output IP datagrams for which no problem
was encountered to prevent their transmission to their
destination, but which were discarded (e.g., for lack of
buffer space). Note that this counter would include
datagrams counted in ipForwDatagrams if any such packets
met this (discretionary) discard criterion.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipOutNoRoutes { ip 12 }
Syntax:
Counter
Definition:
The number of IP datagrams discarded because no route
could be found to transmit them to their destination.
Note that this counter includes any packets counted in
ipForwDatagrams which meet this "no-route" criterion.
Note that this includes any datagarms which a host cannot
route because all of its default gateways are down.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipReasmTimeout { ip 13 }
Syntax:
INTEGER
Definition:
The maximum number of seconds which received fragments
are held while they are awaiting reassembly at this
entity.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipReasmReqds { ip 14 }
Syntax:
Counter
Definition:
The number of IP fragments received which needed to be
reassembled at this entity.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipReasmOKs { ip 15 }
Syntax:
Counter
Definition:
The number of IP datagrams successfully re-assembled.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipReasmFails { ip 16 }
Syntax:
Counter
Definition:
The number of failures detected by the IP re-assembly
algorithm (for whatever reason: timed out, errors, etc).
Note that this is not necessarily a count of discarded IP
fragments since some algorithms (notably the algorithm in
RFC815) can lose track of the number of fragments by
combining them as they are received.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipFragOKs { ip 17 }
Syntax:
Counter
Definition:
The number of IP datagrams that have been successfully
fragmented at this entity.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipFragFails { ip 18 }
Syntax:
Counter
Definition:
The number of IP datagrams that have been discarded
because they needed to be fragmented at this entity but
could not be, e.g., because their "Don't Fragment" flag
was set.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipFragCreates { ip 19 }
Syntax:
Counter
Definition:
The number of IP datagram fragments that have been
generated as a result of fragmentation at this entity.
Access:
read-only.
Status:
mandatory.
5.4.1. The IP Address table
The Ip Address table contains this entity's IP addressing
information.
OBJECT:
-------
ipAddrTable { ip 20 }
Syntax:
SEQUENCE OF IpAddrEntry
Definition:
The table of addressing information relevant to this
entity's IP addresses.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipAddrEntry { ipAddrTable 1 }
Syntax:
IpAddrEntry ::= SEQUENCE {
ipAdEntAddr
IpAddress,
ipAdEntIfIndex
INTEGER,
ipAdEntNetMask
IpAddress,
ipAdEntBcastAddr
INTEGER,
ipAdEntReasmMaxSize
INTEGER (0..65535)
}
Definition:
The addressing information for one of this entity's IP
addresses.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipAdEntAddr { ipAddrEntry 1 }
Syntax:
IpAddress
Definition:
The IP address to which this entry's addressing
information pertains.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipAdEntIfIndex { ipAddrEntry 2 }
Syntax:
INTEGER
Definition:
The index value which uniquely identifies the interface
to which this entry is applicable. The interface
identified by a particular value of this index is the
same interface as identified by the same value of
ifIndex.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipAdEntNetMask { ipAddrEntry 3 }
Syntax:
IpAddress
Definition:
The subnet mask associated with the IP address of this
entry. The value of the mask is an IP address with all
the network bits set to 1 and all the hosts bits set to
0.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipAdEntBcastAddr { ipAddrEntry 4 }
Syntax:
INTEGER
Definition:
The value of the least-significant bit in the IP
broadcast address used for sending datagrams on the
(logical) interface associated with the IP address of
this entry. For example, when the Internet standard
all-ones broadcast address is used, the value will be 1.
This value applies to both the subnet and network
broadcasts addresses used by the entity on this (logical)
interface.
Access:
read-only.
Status:
mandatory.
OBJECT:
-------
ipAdEntReasmMaxSize { ipAddrEntry 5 }
Syntax:
INTEGER (0..65535)
Definition:
The size of the largest IP datagram which this entity can
re-assemble from incoming IP fragmented datagrams
received on this interface.
Access:
read-only.
Status:
mandatory.
5.4.2. The IP Routing table
The IP Routing table contains an entry for each route presently known
to this entity.
OBJECT:
-------
ipRoutingTable { ip 21 }
Syntax:
SEQUENCE OF IpRouteEntry
Definition:
This entity's IP Routing table.
Access:
read-write.
Status:
mandatory.
OBJECT:
-------
ipRouteEntry { ipRoutingTable 1 }
Syntax:
IpRouteEntry ::= SEQUENCE {