Using SNMP for Network Management

gayheadavonΔίκτυα και Επικοινωνίες

27 Οκτ 2013 (πριν από 3 χρόνια και 8 μήνες)

82 εμφανίσεις

Using SNMP for Network Management

http://www.microsoft.com/resources/documentation/windowsnt/4/server/reskit/en
-
us/net/sur_snmp.mspx?mfr=true

Simple Network Management Protocol (SNMP) is a network management standard widely used in
TCP/IP networks and, more recently, with Internet Package Exchange (IPX) networks. Windows NT
Server and Windows NT Workstation 4.0 include an SNMP service that allow
s Windows NT


based
computers to be managed by using SNMP network management programs.

The information in this chapter is for the administrator who needs to understand SNMP and the SNMP
-
based service running under Windows NT 4.0.

This chapter begins with

a review of basic SNMP concepts, and provides a glossary of the network
management terms that are used throughout this chapter. The next two sections describe the SNMP
network management standard and the Windows NT implementation of SNMP. The remaining se
ctions in
the chapter provide information about using and troubleshooting the SNMP service running under
Windows NT. At the end of the chapter there is a list of reference materials that provide detailed
information about SNMP, TCP/IP, and IPX.

Overview o
f SNMP

Simple Network Management Protocol (SNMP) is a network management protocol frequently used in
TCP/IP networks to monitor and manage computers and other devices (such as printers) connected to
the network. SNMP is supported in Windows NT Server and
Windows NT Workstation by the SNMP
service.

As part of the Internet TCP/IP protocol suite, SNMP is defined in the Internet Engineering Task Force
(IETF) Request for Comments (RFCs) 1155, 1157, and 1213. The following table describes these RFCs.

RFC
#

Tit
le

Description

1155

Structure and Identification of Management Information
for TCP/IP
-
based Internets

Defines the structure used to define data
objects in a MIB.

1157

Simple Network Management Protocol (SNMP)

Defines SNMP communication formats
and
operations.

1213

Management Information Base for Network Management
of TCP/IP
-
based Internets: MIB
-
II

Defines basic and industry
-
common types
of managed
-
objects.

Requirements for Network Management

The term
network management

generally refers to specifi
c administrative functions and the ability to
perform these functions from a centralized computer, often referred to as a
management console
.

To perform centralized network management, the managing computer must be able to get data from
other computers on

the network, including the following:



Network protocol identification and statistics




Dynamic identification of computers attached to the network (referred to as
discovery
)




Hardware and software configuration data




Computer performance and
usage statistics




Computer event and error messages




Program and application usage statistics


How SNMP Uses the Registry

The Registry, the operating system database on each Windows NT
-
based computer, contains information
that is needed for network management. The SNMP service accesses the Registry and converts the
information into a format that can be used by third
-
party SNM
P network management programs.



Figure 11.1 The Windows NT Registry


The following sections


"Management Information Base," "Agents," and "Managers"


provide a high
-
level overview of the major software components of SNMP. Windows NT implements SNMP
-
ba
sed MIBs
and an SNMP agent component to provide the necessary framework for SNMP network management.

SNMP uses a glossary of network management terms that may be unfamiliar to some readers. The
following SNMP network management terminology is used in this

chapter.




host

is any network device, including workstation and server computers.




Managed
-
objects

are host hardware and software resources, such as a computer disk partition, that can
be monitored (managed) by a network administrator at another co
mputer on the network.




Each SNMP host (computer) has one or many
management information bases

(MIBs) that contain
information about the managed
-
objects on that computer.





manager

is a software program that sends requests for data to other computer
s on the network.
Typically, the manager includes a user interface (UI) for displaying status and data retrieved from the
network computers and devices.




An
SNMP management console

is any computer running SNMP manager software.




An
agent

is a software program that processes manager requests for data by retrieving data from
managed
-
objects on the computer. The agent program is part of the SNMP service running under
Windows NT.





Management Information Base

A management information base (MIB) is a data file containing the managed
-
object descriptions and
object values. Each host that is to be managed by SNMP must have a MIB that describes the
manageable objects on that host.

Basically, a MIB will define the f
ollowing for every object contained within that MIB:



the association between (1) the host hardware or software component (object) and (2) an object name
and an object identifier.




A definition of the data type used to define the object.




A textual

description of the object.




An index method used for objects that are a complex data type.




The read or write access that is allowed on the object.


RFC 1213 defines an industry
-
standard SNMP MIB referred to as MIB
-
II. Industry vendors, such as
Mic
rosoft, can define additional MIBs that allow unique hardware or software services developed by the
vendor to be monitored and managed by SNMP management consoles.

Note

Additional MIBs that are supported by Windows NT Server are described in Appendix C, "
MIB
Object Types for Windows NT."

Object Identifiers

Each object in a MIB is identified by a universally unique label referred to as an
object
-
identifier
(OID
)
.
The object name space is implemented as a multi
-
part, hierarchical, naming scheme. A hierarchic
al
naming scheme can be viewed as an inverted tree with the branches pointing downward. Each point
where a new branch is added is referred to as a
node
. This OID is internationally accepted and allows
developers and vendors to create new components and res
ources and assign a unique OID to each new
component or resource.

The OID naming scheme is governed by the Internet Engineering Task Force (IETF). The IETF grants
authority for parts of the name space to individual organizations, such as Microsoft. For ex
ample,
Microsoft has the authority to assign the OIDs that can be derived by branching downward from the node
in the MIB name tree that starts at 1.3.6.1.4.1.311.



Figure 11.2 A Managed
-
object Name Hierarchy


SNMP programs use the OID to identify the ob
jects on each computer that can be managed by using
SNMP. For example, when a network administrator requires information about managed
-
objects from
some computer on the network, the SNMP management program sends a message over the network that
requests inf
ormation about the object as identified by the OID. The computer that receives the message
can use the OID to retrieve information from the specific object on the computer and send the information
back to the SNMP management program.

Agents

An agent is an SNMP program that must be installed on each managed computer in an SNMP
-
managed
network. The Windows NT
-
based SNMP service includes an SNMP agent.

The agent program provides an interface to the MIBs and managed
-
objects installed on the comp
uter.
SNMP management programs send management requests to the computers on the network. The agent
program on the computer receives the requests and processes them by retrieving information from the
MIBs on the computer. The agent then sends the requested
information back to the SNMP manager
program that initiated the request.

The Windows NT
-
based SNMP service is an optional service that is installed after TCP/IP is installed on a
Windows NT
-
based computer. After the SNMP service is installed on a computer
, it automatically starts
each time the computer is started.

When the agent program is started on a computer, it waits for SNMP requests from a manager program
on the network management console (computer). When an agent program receives an SNMP message,
i
t performs the requested
get
,

get
-
next
, and
set

operations.

The only operation that an agent spontaneously starts is a
trap
operation to alert the SNMP manager
program that the computer has started, stopped, or is experiencing an extraordinary event (such as disk
-
full) on some managed
-
object on the computer.

In summary, the agent program performs the following operations:



T
桥h
get

operation retrieves a specific value about a managed
-
object, such as available hard disk space,
from the host MIB.



The
get
-
next

operation returns the "next" value by traversing the MIB database of managed
-
object
variables.



The
set

operation
changes the value of a managed
-
object variable. Only variables whose object
definitions allow read/write access can be set.




The
trap

operation sends messages to the SNMP management console when a change or error occurs
in a managed
-
object.

Note

By installation default, the computer software port 161 is used to listen for SNMP messages and
port 162 is used listen for SNMP traps. If you need to run multiple SNMP agents, you can change these
port settings in the
\
systemroot
\

System32
\
Drivers
\
Etc
\
Se
rvice
\
Service file.

Managers

SNMP management programs are referred to as
managers
. Managers obtain data about network devices
and make this information available to a network administrator through textual, graphical, or object
-
oriented user interfaces. The

manager program sends SNMP messages to network hosts. These
messages are received by the agent on the host, and initiate the
get
,
get
-
next
, and
set

operations. The
manager program waits (listens) for the SNMP messages from the agent that contain the resul
ts of the
operation, and displays the information on the SNMP
-
management console or saves the data in a
specified file or database.

As noted earlier, the SNMP service running under Windows NT is an SNMP agent, which is the
necessary framework needed for n
etwork management. However a separate SNMP manager program is
needed to perform management operations.

There are several SNMP manager utilities provided with the Windows NT Server Resource Kit compact
disc. Other network management software can be obtaine
d from Microsoft or from third
-
party vendors.

Windows NT
-
based Implementation of SNMP

The SNMP service running under Windows NT implements SNMP version 1 and provides an SNMP
agent that allows remote, centralized SNMP management of:



Windows NT Server
computers




Windows NT Workstation computers




Windows NT
-
based WINS server computers




Windows NT
-
based DHCP server computers




Windows NT
-
based Internet Information Server computers




LAN Manager server computers

Note

Network Driver Interface Specification (NDIS) 4.0
-
compliant peripheral devices attached to a
Windows NT
-
based computer are also manageable by using the Windows NT
-
based SNMP service. If
the device is to be managed by using SNMP, the device vendor must pro
vide a device .inf file that can be
registered in the Windows NT
-
based Registry.

The Windows NT
-
based SNMP agent is implemented as a service and can be installed on Windows NT
-
based computers that use the TCP/IP and IPX protocols. The TCP/IP protocol must
be installed before
installing SNMP. For more information about installing SNMP, see TCP/IP Help.

Note

You must install TCP/IP to be able to install the SNMP service, even if IPX is installed as the main
network protocol.

The SNMP service is implemented
as a Windows 32
-
bit service by using Windows Sockets over both
TCP/IP and IPX/SPX. The additional Microsoft MIBs for DHCP, WINS, and the Internet Information
Server, extend SNMP management to these Windows NT
-
based services. The agent programs that
impleme
nt these additional MIBs are referred to as
extension
-
agents
. The extension
-
agent programs
work with the master Windows NT
-
based agent program. These Windows NT
-
based extension
-
agents
are implemented as Windows 32
-
bit dynamic
-
link libraries (DLLs).

The fo
llowing diagram shows a simple interaction between an SNMP manager computer and a Windows
NT
-
based computer with an SNMP agent program.



Figure 11.3 SNMP Manager and SNMP Agent Interaction


Windows NT SNMP Files

The following table describes the files that are installed on a Windows NT computer with the SNMP
service installed.

File name

Description

Dhcpmib.dll

DHCP MIB extension
-
agent DLL is available only when the DHCP server is installed on a
computer running


Windows NT Server.

Iis.dll

Internet Information Server DLL is available only if the Internet Information Server is
installed on a computer running Windows NT Server.

Inetmib1.dll

MIB
-
II extension
-
agent DLL.

Lmmib2.dll

LAN Manager extension
-
agent DLL.

Mgmtapi.dll

A Windows NT
-
based SNMP manager API that listens for manager requests, and sends
the requests to and receives responses from SNMP agents.

Mib.bin

Installed with the SNMP service and used by the management API, Mgmtapi.dll, to map
text
-
based

object names to numerical OIDs.

Snmp.exe

SNMP agent service, a master (proxy) agent that accepts manager program requests and
forwards the requests to the appropriate sub
-
agent
-
extension DLL for processing.

Snmptrap.exe

Receives SNMP traps from the SN
MP agent and forwards them to the SNMP manager API
on the management console. A background process, Snmptrap.exe is started only when
the SNMP manager API receives a manager request for traps.

Winsmib.dll

WINS MIB extension
-
agent DLL, available only whe
n the WINS server is installed on a
computer running Windows NT Server.

MIB Implementation Notes

The Windows NT
-
based SNMP service includes MIB
-
II, based on RFC 1213, LAN Manager MIB
-
II, and
Microsoft proprietary MIBs for DHCP, Internet Information Server, and WINS servers. Appendix C, "MIB
Object Types for Windows NT," contains information about the
Windows NT
-
based MIBs, and a
description of each object in the MIB.

The Windows NT
-
based SNMP service supports multiple MIBs through an agent application programming
interface (API). The separate extension
-
agent DLL is used to access the Windows NT
-
based
MIBs. When
the SNMP service is started, it loads the SNMP extension
-
agent DLLs. The extension
-
agent DLLs must
be defined in the Registry in order to be loaded.

This use of DLLs in the SNMP service architecture allows new MIBs to be easily added. Microsoft

and
third
-
party developers can develop MIBs for new hardware and software components and easily integrate
the new functionality by using SNMP.

The MIB name space assigned to Microsoft by the IETF starts at the node labeled
1.3.6.1.4.1.311
.
Microsoft has
the authority to assign objects and OIDs to all objects that are developed below that node.

The following table identifies the Windows NT
-
based MIBs and top
-
most object (base object) from which
all other objects in the MIB are derived. When the SNMP servi
ce is started, each extension
-
agent sends
the OID for the base object in its MIB to the master agent program. This process identifies to the master
agent the MIBs and managed objects that are actually installed on the computer.



MIB name

Base object name

Base object
identifier (OID)

Description

Internet MIB
-
II



iso.org.dod.internet.

mgmt.mib
-
2

1.3.6.1.2.1

Defines objects essential for either
configuration or fault analysis.
Internet MIB
-
II is defined in RFC
1213.

LAN Manager
MIB
-
II



iso.org.dod.internet.

private.enterprise.

lanmanager

1.3.6.1.4.1.77

Defines objects that include such
items as statistical, share, session,
user, and logon information.

Microsoft DHCP
server MIB



iso.org.dod.internet.

private.enterprise.

microsoft.softw
are.

dhcp

1.3.6.1.4.1.311.1.3

Contains statistics for the DHCP
server, and DHCP scope
information.

Microsoft Internet
Information
Server MIB

iso.org.dod.internet.
private.enterprise.
microsoft.software. iis

1.3.6.1.4.1.311.1.7

The FTP, Gopher, and HTTP
server
MIBs are derived from the Internet
Information Server base object.

Microsoft WINS
server MIB



iso.org.dod.internet.

private.enterprise.

microsoft.software.

wins

1.3.6.1.4.1.311.1.2

Contains information about the
WINS server, including statistics,
database information, and push and
pull data.

SNMP Security Implementation Notes

The SNMP security service is referred to as an
authentication

service. Simply put, a management request
contained within an authenticated SNMP message is processed; a message that cannot be authenticated
is not processed.

SNMP uses
community names

to authenticate messages. The community name can be thought of as a
password shared by the SNMP management consoles and the SNMP managed hosts. All SNMP
messages must contain a community name. The SNMP agent that receives an SNMP message checks
(authenticates) the community name with the community name or names with which
the SNMP service is
configured. If the message contains a known community name, the message is processed. If the
message contains a community name that is not configured on the host, the message is rejected and the
host (optionally) sends a trap message to

an SNMP management console. The trap message alerts the
SNMP management console that a message authentication failure occurred at that host.

The default community name when the SNMP service is installed on a Windows NT
-
based computer is
"public." Additio
nal community names can be added or removed by selecting
SNMP Service

from the
Network Services

tab.

If you remove all the community names, including the default name, Public
, the SNMP service on that
Windows NT
-
based computer will authenticate and process SNMP messages containing
any

community
name. This may or may not be desirable, but is expected behavior, as described in RFC 1157:

An SNMP message originated by an SNMP app
lication entity that in fact belongs to the SNMP community
named by the community component of said message is called an authentic SNMP message. The set of
rules by which an SNMP message is identified as an authentic SNMP message for a particular SNMP
comm
unity is called an authentication scheme. An implementation of a function that identifies authentic
SNMP messages according to one or more authentication schemes is called an authentication
service.Clearly, effective management of administrative relationsh
ips among SNMP application entities
requires authentication services that (by the use of encryption or other techniques) are able to identify
authentic SNMP messages with a high degree of certainty. Some SNMP implementations may wish to
support only a triv
ial authentication service that identifies all SNMP messages as authentic SNMP
messages.

When there are no community names identified, the SNMP service implements the behavior as described
in the preceding selection from RFC 1157.

Planning for SNMP Instal
lation

Before installing the SNMP service, an administrator must identify the following information:



The contact person and location for the administrator of the local computer.




Community names that can be shared by hosts on the network.




IP add
ress, IPX address, or network computer name of the SNMP management console, or consoles,
that will be the destination for trap messages generated by computers within a specific community. (Not
all SNMP management consoles must also be trap destinations.)

Agent Configuration

You configure the SNMP agent by selecting the
Agent

tab on the
Microsoft SNMP Properties

page
.
By
default, the optional agent configuration options are checked, as illustrated in the following figure. You
only need to add the name of the person to contact, such as the network administrator, and the location
of the contact.


Figure 11.4 Configuring

the SNMP Agent


Community Names

Community names provide a rudimentary security scheme for the SNMP service. You can add and delete
community names by using the
Security

tab on the
Microsoft SNMP Properties

page
.
You can also
filter the type of packets tha
t the computer will accept. The following figure shows the
Security

tab.


Figure 11.5 Configuring SNMP Security


You must configure the SNMP service with at least one community name. The installation default is the
Public community name. You can delete o
r change the default community name and add multiple
community names.

There is no relationship between community names and domain or workgroup names. Community names
serve as a shared password for groups of hosts on the network and should be selected and
changed as
you would any other password. Members of a community (hosts that share the same community name)
are typically grouped by their physical proximity.

When the SNMP agent receives an SNMP request that does not contain the correct community name or
that came from an unknown host, the SNMP agent can send a trap to one or more trap destinations
(SNMP manager programs). The trap message indicates that the request failed authentication.

In the following example, there are two communities


Terraflora an
d Public.



Figure 11.6 SNMP Community Names


Only the agents and managers that are configured with the same community name can communicate
with each other.



Agent 1 can send traps and other messages to Manager 2 because they are both members of the Te
rra
Flora community.



Agent 2 through Agent 4 can send traps and messages to Manager 1 because they are all members of
the Public (default) community.

The community names that are configured by using the
Security
tab are used when configuring Trap
Destinations.

Trap Destinations

The SNMP agent generates trap messages, which are sent to an SNMP management console, the trap
destination. Trap messages can be generated for changes such as host system startup, shutdown
, or
password violation. Trap destinations can be configured by a user, but the occurrences which generate a
trap message are internally defined by the SNMP agent.

Trap destinations are identified by a computer name, IP address, or IPX address of the host

or hosts on
the network to which you want the trap messages sent. The trap destination must be a host that is
running an SNMP manager program.

You configure the trap destination on a Windows NT
-
based computer by using the
Traps

tab on the
Microsoft SNMP
Properties

page to enter the host name, IP address, or IPX address of the computer or
computers running an SNMP manager program. The following figure shows the
Traps

tab of the
Microsoft SNMP Properties

page.


Figure 11.7 Configuring SNMP Traps




Using
SNMP

When the SNMP service is installed, a network administrator can:



View and change parameters in the LAN Manager and MIB
-
II MIBs by using SNMP manager programs.




Monitor and configure parameters for any WINS servers on the network by using SNMP
manager
programs.




Monitor DHCP servers by using SNMP manager programs.




Use Performance Monitor to monitor TCP/IP
-
related performance counters which are ICMP, IP, Network
Interface, TCP, UDP, DHCP, FTP, WINS, and Internet Information Server performa
nce counters.




Use the Windows NT Server Resource Kit utilities to perform simple SNMP manager functions.


The following table describes SNMP
-
related utilities and files provided on the Resource Kit compact disc.

File name

Description

Dhcp.mib

DHCP
server objects. See Appendix C, "MIB Object Types for Windows NT."

Wins.mib

Microsoft WINS server managed
-
objects. See Appendix C, "MIB Object Types for
Windows NT."

Inetsrv.mib

Internet Information Server managed
-
objects. See Appendix C, "MIB Object Ty
pes for
Windows NT."

FTP.mib

FTP server managed
-
objects. See Appendix C, "MIB Object Types for Windows NT."

Gopherd.mib

Gopher server managed
-
objects. See Appendix C, "MIB Object Types for Windows NT."

Http.mib

HTTP server managed
-
objects. See Appendix

C, "MIB Object Types for Windows NT."

Lmmib2.mib

LAN Manager MIB
-
II. See Appendix C, "MIB Object Types for Windows NT."

Mib_ii.mib

MIB
-
II. See Appendix C, "MIB Object Types for Windows NT."

Smi.mib

Structure of Management Information MIB, as specified
in RFC 1155. This file contains the
global definitions used to define the objects in the other MIBs.

Mibcc.exe

SNMP MIB compiler used to produce a new Mib.bin that includes additional MIBs, for
example, the Wins.mib.

Perf2mib.exe

MIB builder tool. See t
he section "Using Performance Monitor Counters with SNMP" later
in this chapter.

Snmputil.exe

A simple SNMP browser manager application that implements
Get
,
Get Next
,
Walk
, and
Trap

network management operations to obtain information from Windows NT
-
based
hosts. This application is also provided in the Windows 32
-
bit SDK.

Snmpmon.exe

SNMP Monitor is a utility that can monitor SNMP MIB objects on any number of remote
hosts, and optio
nally log the results in an ODBC database. Snmpmon.exe uses an .ini file,
for example Perfmib.ini.

For information on how to use any of the Windows NT
-
based Resource Kit utilities, see Resource Kit
Tools Help.

Starting and Stopping the SNMP Service

Afte
r the SNMP service has been installed, it automatically starts when the computer is started and so
you will usually not need to start the SNMP service.

However, if you stop SNMP, you must then restart it
because it does not automatically restart. Stopping
a service cancels any network connections the service
is using.

You can start and stop the SNMP service at the command prompt by typing the commands
net start
snmp and

net stop snmp.
You can also point to
Control Panel

and double
-
click the
Services

icon,
then
select
SNMP

and click the
Start

or
Stop

service buttons.

You must stop and restart the SNMP service to add new extension
-
agent DLLs and MIBs.

Note

The syntax for the
net start snmp

and
net stop snmp

commands has changed in Windows NT
4.0. SNMP error

logging parameters are not supported and have been replaced by improved SNMP error
handling in the Windows NT Event Log. The syntax for these commands is:

net start snmp


net stop snmp


Using SNMP to Manage DHCP, WINS, and Internet Information Servers

If

you have installed the DHCP server, Internet Information Server, or WINS server software on a
Windows NT
-
based computer on the network, you can monitor the DHCP, Internet Information Server, or
WINS services by using an SNMP manager program.

The Windows
NT
-
based DHCP server objects and Internet Information Server server objects can be
monitored, but not configured, using SNMP.

WINS server objects can be configured and monitored by using SNMP. All but a few of the WINS
configuration parameters that can be

set by editing the Registry can also be set by using SNMP. For
information about which WINS parameters can be set by using SNMP, refer to the description of the
WINS MIB in Appendix C, "MIB Object Types for Windows NT."

WINS objects that are defined with
Access read
-
write

can be configured by using SNMP.

Using Performance Monitor Counters with SNMP

All Performance Monitor counters installed on a computer can be viewed by using SNMP. To do this, use
the Perf2MIB utility provided on the Windows NT Server Re
source Kit compact disc to create a new MIB
file which enumerates the counters in which you are interested. For additional information on how to use
the Perf2mib.exe utility, see Resource Kit Tools Help.

Troubleshooting SNMP

This section discusses problems that you might encounter using SNMP, and what to do to resolve them.

Using the Event Viewer to Find SNMP Errors

SNMP error handling has been improved in Windows NT Server and Windows NT Workstation version
4.0. Manual confi
guration of SNMP error
-
logging parameters has been replaced by improved error
handling that is integrated with the Event Viewer. Use the Event Viewer if you suspect a problem with the
SNMP Service.

Note

Refer to the
Windows NT Server Resource Guide

for de
tailed information about using the Event
Viewer.

To use Event Viewer


1.

From the
Start

menu, point to
Programs
.


2.

Click Administrative Tools on the Programs menu.


3.

Double
-
click
Event Viewer

to display the System Log.


4.

If any is any event is identified as SNMP in the Source column, double
-
click that row to display the
Event Detail
.


The following figure illustrates an SNMP event display in the
Event Viewer
.


Figure 11.8 SNMP Event Message


Modifying SNMP Parameters in

the Registry

SNMP parameters and information about the SNMP extension
-
agent DLLs are contained in the Registry.
You can view or change this information by using the Registry Editor (Regedt32.exe).

To start the Registry Editor


1.

Click the
Start

button a
nd click
Run
.


2.

Type
regedt32

in the command line box.


Warning
Using Registry Editor incorrectly can cause serious, system
-
wide problems that may require
you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting
from the incorrect use of the Registry Editor can be solved.

Wi
ndows NT
-
based SNMP parameters are contained in the Registry in the following key:

HKEY_LOCAL_MACHINE
\
System
\
CurrentControlSet
\
Services
\
SNMP
\
Parameters


The following table describes the SNMP parameters contained in the Registry.

Registry parameter

Description

EnableAuthenticationTraps

Units: Boolean

Range: 0 (Off) or 1 (On)

Default: On

A value of On (1) indicates that the SNMP service sends a trap whenever it
receives a request that does not match any community name or host filter in
its lists. Off

(0) indicates that the SNMP service does not send a trap when
this occurs.

ExtensionAgents

Contains information about each of the extension
-
agent DLLs to load.

ValidCommunities

Units: names

Range:



Default: public

Specifies one or more community name
s defining groups of hosts from
which the SNMP service will accept requests.

TrapConfiguration

Units: name

Range:



Default:


Specifies one or more host names, IP addresses, or IPX addresses defining
hosts to which the SNMP service sends traps. Under th

TrapConfiguration

key, there is a key for each community. Under the
ValidCommunities

key, there are trap destination values for that
community.

Timeout on WINS Server Queries

When querying a WINS server, it might be necessary to increase the SNMP timeout period on the SNMP
management system. If some WINS queries work and others time out, increase the timeout period.

No Counters Appear in Performance Monitor

You must install t
he SNMP service to see any of the TCP/IP, Internet Control Message Protocol (ICMP),
Network Interface, or UDP performance counters in Performance Monitor. When the SNMP service is
installed, the following TCP/IP
-
related counters are added to Performance Mo
nitor:



ICMP









Network Interface




TCP




啄U


SNMP is not automatically installed when you install TCP/IP. See TCP/IP Help for information about
installing and configuring SNMP on your local computer.

For more information about Performance Monitor and counters, refer to the
Windows NT Server
Resource Guide.


Note

When the IPX protocol is used as the main network protocol, the TCP/IP objects that can be
monitored by using SNMP are null.

Error Using an IP
X Address as a Trap Destination

If you enter an IPX address as a trap destination when installing the SNMP service, the following error
message may appear when you restart your computer:

Error 3


This problem occurs if the IPX address has been entered inc
orrectly, using a comma or hyphen to
separate a network number and a MAC address. For example, an SNMP manager program such as HP
OpenView may normally accept an address such as this: 00008022,0002C0
-
F7AABD. However, the
Windows NT
-
based SNMP agent does no
t recognize an address using a comma or hyphen between the
network number and MAC address.

The address used for a trap destination must use the "8.12" format for the network number and Media
Access Control (MAC) address.

To correct this problem, enter th
e IPX address for the trap destination in the 8.12 format. For example,
the following format is valid:

xxxxxxxx
.
yyyyyyyyyyyy


where
xxxxxxxx

is the network number and
yyyyyyyyyyyy

is the MAC address.



Reference Materials


The following books contain more information about SNMP.

Network Management: A Practical Perspective

by Allan Leinwand and Karen Fang

Addison
-
Wesley Publishing Company, Inc 1993

ISBN 0
-
201
-
52771
-
5
SNMP, SNMPv2, and CMIP: The Practical Guide to Network
-
Man
agement
Standards

by William Stallings

Addison
-
Wesley Publishing Company, Inc 1993

ISBN 0
-
201
-
63331
-
0
The Simple Book: An Introduction to Management of TCP/IP
-
based
Internets

by Marshall T. Rose

Prentice
-
Hall, Inc., 1994

ISBN 0
-
13
-
177254
-
6
Internetworking
with TCP/IP

Volume 1: Principles, Protocols, and Architecture
(third edition)

by Douglas E. Comer

Prentice
-
Hall, Inc., 1991

ISBN 0
-
13
-
468505
-
9

The following Requests for Comments (RFCs) are published by the Internet Engineering Task Force
(IETF) and other

working groups. The RFCs that define SNMP are listed in the following table.

RFC

Title

1155

Structure and Identification of Management Information for TCP/IP
-
based Internets

1157

Simple Network Management Protocol

1213

Management Information Base for
Network Management of TCP/IP
-
based internets: MIB
-
II

RFCs can be obtained via FTP from:



nis.nsf.net




nisc.jvnc.net




venera.isi.edu




wuarchive.wustl.edu




src.doc.ic.ac.uk




ftp.concert.net




ds.internic.net
, or




nic.ddn.mil