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SNMP.CONF


Section: Net-SNMP (5)
Updated: 29 Jun 2005
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NAME

snmp.conf – configuration files for the Net-SNMP applications
 

DESCRIPTION

Applications built using the Net-SNMP libraries typically use one or
more configuration files to control various aspects of their operation.
These files (snmp.conf and snmp.local.conf) can be located
in one of several locations, as described in the snmp_config(5)
manual page.

In particular, /etc/snmp/snmp.conf is a common file,
containing the settings shared by all users of the system.
~/.snmp/snmp.conf is a personal file, with the settings
specific to a particular user.
 

IMPORTANT NOTE

Several of these directives may contain sensitive information
(such as pass phrases). Configuration files that include such
settings should only be readable by the user concerned.

As well as application-specific configuration tokens, there are
several directives that relate to standard library behaviour,
relevant to most Net-SNMP applications. Many of these correspond
to standard command-line options, which are described in the
snmpcmd(1) manual page.

These directives can be divided into several distinct groups.
 

CLIENT BEHAVIOUR


defDomain application domain

The transport domain that should be used for a certain application type unless
something else is specified.
defTarget application domain target

The target that should be used for connections to a certain application if the
connection should be in a specific domain.
defaultPort PORT

defines the default UDP port that client SNMP applications will
attempt to connect to. This can be overridden by explicitly
including a port number in the AGENT specification.
See the snmpcmd(1) manual page for more details.

If not specified, the default value for this token is 161.
defVersion (1|2c|3)

defines the default version of SNMP to use.
This can be overridden using the -v option.
defCommunity STRING

defines the default community to use for SNMPv1 and SNMPv2c requests.
This can be overridden using the -c option.

alias NAME DEFINITION

Creates an aliased tied to NAME for a given transport definition. The
alias can the be referred to using an alias: prefix. Eg, a line of
"alias here udp:127.0.0.1:6161" would allow you to use a destination
host of "alias:here" instead of "udp:127.0.0.1:6161". This becomes
more useful with complex transport addresses involving IPv6 addresses,
etc.
dumpPacket yes

defines whether to display a hexadecimal dump of the raw SNMP requests
sent and received by the application.
This is equivalent to the -d option.
doDebugging (1|0)

turns on debugging for all applications run if set to 1.

debugTokens TOKEN[,TOKEN...]

defines the debugging tokens that should be turned on when
doDebugging is set.
This is equivalent to the -D option.

16bitIDs yes

restricts requestIDs, etc to 16-bit values.

The SNMP specifications define these ID fields as 32-bit quantities,
and the Net-SNMP library typically initialises them to random values
for security.
However certain (broken) agents cannot handle ID values greater than
2^16 – this option allows interoperability with such agents.
clientaddr [<transport-specifier>:]<transport-address>

specifies the source address to be used by command-line applications
when sending SNMP requests. See snmpcmd(1) for more information
about the format of addresses.

This value is also used by snmpd when generating notifications.

clientaddrUsesPort no

specifies, if clientaddr option contains a port number. Set this option
to "yes", if clientaddr contains a port number and this port should
be used for sending outgoing SNMP requests.
clientRecvBuf INTEGER

specifies the desired size of the buffer to be used when receiving
responses to SNMP requests.
If the OS hard limit is lower than the clientRecvBuf value,
then this will be used instead.
Some platforms may decide to increase the size of the buffer
actually used for internal housekeeping.

This directive will be ignored if the platforms does not support
setsockopt().
clientSendBuf INTEGER

is similar to clientRecvBuf, but applies to the size
of the buffer used when sending SNMP requests.
noRangeCheck yes

disables the validation of varbind values against the MIB definition
for the relevant OID.
This is equivalent to the -Ir option.

This directive is primarily relevant to the snmpset command,
but will also apply to any application that calls snmp_add_var()

with a non-NULL value.

noTokenWarnings

disables warnings about unknown config file tokens.
reverseEncodeBER (1|yes|true|0|no|false)

controls how the encoding of SNMP requests is handled.

The default behaviour is to encode packets starting from the end of
the PDU and working backwards.
This directive can be used to disable this behaviour, and build
the encoded request in the (more obvious) forward direction.

It should not normally be necessary to change this setting, as
the encoding is basically the same in either case – but working
backwards typically produces a slightly more efficient encoding,
and hence a smaller network datagram.


 

SNMPv3 SETTINGS


defSecurityName STRING

defines the default security name to use for SNMPv3 requests.
This can be overridden using the -u option.
defSecurityLevel noAuthNoPriv|authNoPriv|authPriv

defines the default security level to use for SNMPv3 requests.
This can be overridden using the -l option.

If not specified, the default value for this token is noAuthNoPriv.



Note:

authPriv is only available if the software has been compiled
to use the OpenSSL libraries.

defPassphrase STRING

defAuthPassphrase STRING

defPrivPassphrase STRING

define the default authentication and privacy pass phrases to use
for SNMPv3 requests.
These can be overridden using the -A and -X options respectively.

The
defPassphrase

value will be used for the authentication and/or privacy pass phrases
if either of the other directives are not specified.

defAuthType MD5|SHA

defPrivType DES|AES

define the default authentication and privacy protocols to use for
SNMPv3 requests.
These can be overridden using the -a and -x options respectively.

If not specified, SNMPv3 requests will default to MD5 authentication
and DES encryption.


Note:

If the software has not been compiled to use the OpenSSL libraries,
then only MD5 authentication is supported.
Neither SHA authentication nor any form of encryption will be available.

defContext STRING

defines the default context to use for SNMPv3 requests.
This can be overridden using the -n option.

If not specified, the default value for this token is the default context
(i.e. the empty string "").
defSecurityModel STRING

defines the security model to use for SNMPv3 requests.
The default value is "usm" which is the only widely
used security model for SNMPv3.
defAuthMasterKey 0xHEXSTRING

defPrivMasterKey 0xHEXSTRING

defAuthLocalizedKey 0xHEXSTRING

defPrivLocalizedKey 0xHEXSTRING

define the (hexadecimal) keys to be used for SNMPv3 secure communications.
SNMPv3 keys are frequently derived from a passphrase, as discussed in
the defPassphrase section above. However for improved security a
truely random key can be generated and used instead (which would
normally has better entropy than a password unless it is
amazingly long).
The directives are equivalent to the short-form
command line options -3m, -3M, -3k, and -3K.

Localized keys are
master keys which have been converted to a unique key which is only
suitable for on particular SNMP engine (agent). The length of the key
needs to be appropriate for the authentication or encryption type
being used (auth keys: MD5=16 bytes, SHA1=20 bytes;
priv keys: DES=16 bytes (8
bytes of which is used as an IV and not a key), and AES=16 bytes).
sshtosnmpsocketperms PATH

Sets the path of the sshtosnmp socket created by an application
(e.g. snmpd) listening for incoming ssh connections through the
sshtosnmp unix socket.
sshtosnmpsocketperms MODE [OWNER [GROUP]]

Sets the mode, owner and group of the sshtosnmp socket created by
an application (e.g. snmpd) listening for incoming ssh connections
through the sshtosnmp unix socket. The socket needs to be read/write
privileged for SSH users that are allowed to connect to the SNMP
service (VACM access still needs to be granted as well, most likely
through the TSM security model).


 

SERVER BEHAVIOUR


persistentDir DIRECTORY

defines the directory where snmpd and snmptrapd store
persistent configuration settings.

If not specified, the persistent directory defaults to
/var/lib/net-snmp
noPersistentLoad yes

noPersistentSave yes

disable the loading and saving of persistent configuration information.


Note:

This will break SNMPv3 operations (and other behaviour that relies
on changes persisting across application restart). Use With Care.

tempFilePattern PATTERN

defines a filename template for creating temporary files,
for handling input to and output from external shell commands.
Used by the mkstemp() and mktemp() functions.

If not specified, the default pattern is "/var/run/net-snmp/snmp-tmp-XXXXXX".
serverRecvBuf INTEGER

specifies the desired size of the buffer to be used when receiving
incoming SNMP requests.
If the OS hard limit is lower than the serverRecvBuf value,
then this will be used instead.
Some platforms may decide to increase the size of the buffer
actually used for internal housekeeping.

This directive will be ignored if the platforms does not support
setsockopt().
serverSendBuf INTEGER

is similar to serverRecvBuf, but applies to the size
of the buffer used when sending SNMP responses.

 

MIB HANDLING


mibdirs DIRLIST

specifies a list of directories to search for MIB files.
This operates in the same way as the -M option –
see snmpcmd(1) for details.
Note that this value can be overridden by the
MIBDIRS

environment variable, and the -M option.

mibs MIBLIST

specifies a list of MIB modules (not files) that should be loaded.
This operates in the same way as the -m option –
see snmpcmd(1) for details.
Note that this list can be overridden by the
MIBS

environment variable, and the -m option.

mibfile FILE

specifies a (single) MIB file to load, in addition to the
list read from the mibs token (or equivalent configuration).
Note that this value can be overridden by the
MIBFILES

environment variable.

showMibErrors (1|yes|true|0|no|false)

whether to display MIB parsing errors.
commentToEOL (1|yes|true|0|no|false)

whether MIB parsing should be strict about comment termination.
Many MIB writers assume that ASN.1 comments extend to the end of
the text line, rather than being terminated by the next "–" token.
This token can be used to accept such (strictly incorrect) MIBs.

Note that this directive was previous (mis-)named strictCommentTerm,
but with the reverse behaviour from that implied by the name.
This earlier token is still accepted for backwards compatibility.

mibAllowUnderline (1|yes|true|0|no|false)

whether to allow underline characters in MIB object names and
enumeration values.
This token can be used to accept such (strictly incorrect) MIBs.
mibWarningLevel INTEGER

the minimum warning level of the warnings printed by the MIB parser.

 

OUTPUT CONFIGURATION


logTimestamp (1|yes|true|0|no|false)

Whether the commands should log timestamps with their error/message
logging or not. Note that output will not look as pretty with
timestamps if the source code that is doing the logging does
incremental logging of messages that are not line buffered before
being passed to the logging routines. This option is only used when file logging is active.
printNumericEnums (1|yes|true|0|no|false)

Equivalent to
-Oe.

printNumericOids (1|yes|true|0|no|false)

Equivalent to
-On.

dontBreakdownOids (1|yes|true|0|no|false)

Equivalent to
-Ob.

escapeQuotes (1|yes|true|0|no|false)

Equivalent to
-OE.

quickPrinting (1|yes|true|0|no|false)

Equivalent to
-Oq.

printValueOnly (1|yes|true|0|no|false)

Equivalent to
-Ov.

dontPrintUnits (1|yes|true|0|no|false)

Equivalent to
-OU.

numericTimeticks (1|yes|true|0|no|false)

Equivalent to
-Ot.

printHexText (1|yes|true|0|no|false)

Equivalent to
-OT.

hexOutputLength integer

Specifies where to break up the output of hexadecimal strings.
Set to 0 to disable line breaks. Defaults to 16.
suffixPrinting (0|1|2)

The value 1 is equivalent to
-Os

and the value 2 is equivalent to
-OS.

oidOutputFormat (1|2|3|4|5|6)

Maps -O options as follow: -Os=1, -OS=2, -Of=3, -On=4, -Ou=5.
The value 6 has no matching -O option. It suppresses output.
extendedIndex (1|yes|true|0|no|false)

Equivalent to
-OX.

noDisplayHint (1|yes|true|0|no|false)

Disables the use of DISPLAY-HINT information when parsing indices and
values to set. Equivalent to
-Ih.


 

FILES

/etc/snmp/snmp.conf,
/etc/snmp/snmp.local.conf – common configuration settings

~/.snmp/snmp.conf – user-specific configuration settings
 

SEE ALSO

snmp_config(5), read_config(3), snmpcmd(1).



 

Index



NAME

DESCRIPTION

IMPORTANT NOTE

CLIENT BEHAVIOUR

SNMPv3 SETTINGS

SERVER BEHAVIOUR

MIB HANDLING

OUTPUT CONFIGURATION

FILES

SEE ALSO



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