net-snmp: introduction
SNMP is a protocol that enables server remote-info-exchange. Which according to wikipedia: it [collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior].
It is short for simple network management protocol. Typically, routers, switches, servers, workstations, printers supports it.
If need to test snmp locally, I suggest install net-snmp from source from tarball fetched from here (choose newest version).
Download and ./configure --prefix=/usr & make & make install should work.
Here is a file that most demonstrates the most widely used mib file.
And here is a tutorial that helps you walk through mib file content creation step by step.
possible values of certain fields:
|
关键字 |
说明 |
备注 |
|
objectname |
被管理对象的名字 |
必须以小写字母开头 |
|
OBJECT-TYPE |
每一个叶子对象所必须的关键字 |
|
|
SYNTAX |
被管理对象类型的关键字 |
Counter(计数) Gauge(标准) DisplayString(显示字符串) Interger(整数) TimeTicks（时间戳） NetworkAddress(网络地址) IpAddress（Ipv4地址） |
|
MAX-ACCESS |
该节点支持的访问方式 |
read-only(只读) read-write(读写) read-create(读和创建) no-accessible(不可访问) |
|
STATUS |
该节点的状态 |
current (当前的) deprecated (反对的) obsolete(废弃的) |
|
DESCRIPTION |
对被管理对象的功能、特征等进行描述的关键字 |
|
table fields:
|
关键字 |
说明 |
备注 |
|
tablename |
表格名 |
xxxxTable首字母小写 |
|
Entrytype |
表对象名 |
XxxxEntry首字母大写 |
|
not-accessible |
访问方式 |
此处必须是not-accessible |
|
entryname |
行名 |
和XxxxEntry名相同，首字母小写xxxxEntry |
|
description |
描述信息 |
|
After writing an mib file, it is now time to generate .c & .h files which need to be used to generate the application that supply data to snmpd daemon.
Use the mib2c application:
# suppose we created a mib file called "YOUR-MIB.txt" in /usr/share/snmp/mibs env MIBS="+YOUR-MIB" mib2c -c mib2c.<tbd>.conf MIB-MODULE-NAME
modify the .c file where XXX exists to supply the needed info into snmp daemon.
According to here:
we have 3 ways of let the snmp daemon accepting our mib info:
1. hard code into snmp application by sending the .c .h files into snmp/agent/mibgroup/ and do:
./configure --prefix=/usr --with-mib-modules="MIB-MODULE-NAME" make && make install
snmpd -c /etc/snmp/snmpd.conf # notice in the conf file the OID should be specified.
2. let snmp load our lib at run time, to do this, modify snmpd.conf file: dlmod MIB-MODULE-NAME path/to/lib.so (note: I have not tested this method)
snmpd -f -L -DMIB-MODULE-NAME,dlmod -c /etc/snmp/snmpd.conf
3. agentx module: compile snmp such that it supports agentx;
after that add "master agentx" to snmpd.conf file and start it by snmpd -c /etc/snmp/snmpd.conf
compile .c .h file as:
net-snmp-config --compile-subagent PROGNAME file.c
# then make sure the /var/agentx/master exists
./PROGNAME &
--------
configure huawei switch of snmp, by:
[S5700]snmp-agent sys-info version v2c [S5700]snmp-agent community read public
unconfigure huawei snmpd by adding undo before the above commands.
configure cisco switch:
Router(config)#snmp-server community public RO
unconfigure by adding "no" before the above commands.
------Conclusion of steps of adding new info into snmp mentioned above:
1. write a mib file 2. generate .c .h file with mib file with appropriate mib2c conf file 3. start snmpd daemon 4. compile .c .h file 5. run subagent to supply data into snmpd
---quote of example mib file----
NET-SNMP-EXAMPLES-MIB DEFINITIONS ::= BEGIN -- -- Example MIB objects for agent module example implementations -- IMPORTS MODULE-IDENTITY, OBJECT-TYPE, Integer32, NOTIFICATION-TYPE FROM SNMPv2-SMI SnmpAdminString FROM SNMP-FRAMEWORK-MIB netSnmp FROM NET-SNMP-MIB RowStatus, StorageType FROM SNMPv2-TC InetAddressType, InetAddress FROM INET-ADDRESS-MIB ; netSnmpExamples MODULE-IDENTITY LAST-UPDATED "200406150000Z" ORGANIZATION "www.net-snmp.org" CONTACT-INFO "postal: Wes Hardaker P.O. Box 382 Davis CA 95617 email: net-snmp-coders@lists.sourceforge.net" DESCRIPTION "Example MIB objects for agent module example implementations" REVISION "200406150000Z" DESCRIPTION "Corrected notification example definitions" REVISION "200202060000Z" DESCRIPTION "First draft" ::= { netSnmp 2 } -- -- top level structure -- netSnmpExampleScalars OBJECT IDENTIFIER ::= { netSnmpExamples 1 } netSnmpExampleTables OBJECT IDENTIFIER ::= { netSnmpExamples 2 } netSnmpExampleNotifications OBJECT IDENTIFIER ::= { netSnmpExamples 3 } netSnmpExampleNotificationPrefix OBJECT IDENTIFIER ::= { netSnmpExampleNotifications 0 } netSnmpExampleNotificationObjects OBJECT IDENTIFIER ::= { netSnmpExampleNotifications 2 } -- netSnmpTutorial OBJECT IDENTIFIER ::= { netSnmpExamples 4 } -- -- Example scalars -- netSnmpExampleInteger OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS read-write STATUS current DESCRIPTION "This is a simple object which merely houses a writable integer. It's only purposes is to hold the value of a single integer. Writing to it will simply change the value for subsequent GET/GETNEXT/GETBULK retrievals. This example object is implemented in the agent/mibgroup/examples/scalar_int.c file." DEFVAL { 42 } ::= { netSnmpExampleScalars 1 } netSnmpExampleSleeper OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS read-write STATUS current DESCRIPTION "This is a simple object which is a basic integer. It's value indicates the number of seconds that the agent will take in responding to requests of this object. This is implemented in a way which will allow the agent to keep responding to other requests while access to this object is blocked. It is writable, and changing it's value will change the amount of time the agent will effectively wait for before returning a response when this object is manipulated. Note that SET requests through this object will take longer, since the delay is applied to each internal transaction phase, which could result in delays of up to 4 times the value of this object. This example object is implemented in the agent/mibgroup/examples/delayed_instance.c file." DEFVAL { 1 } ::= { netSnmpExampleScalars 2 } netSnmpExampleString OBJECT-TYPE SYNTAX SnmpAdminString MAX-ACCESS read-write STATUS current DESCRIPTION "This is a simple object which merely houses a writable string. It's only purposes is to hold the value of a single string. Writing to it will simply change the value for subsequent GET/GETNEXT/GETBULK retrievals. This example object is implemented in the agent/mibgroup/examples/watched.c file." DEFVAL { "So long, and thanks for all the fish!" } ::= { netSnmpExampleScalars 3 } -- -- Example Tables -- netSnmpIETFWGTable OBJECT-TYPE SYNTAX SEQUENCE OF NetSnmpIETFWGEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "This table merely contains a set of data which is otherwise useless for true network management. It is a table which describes properies about a IETF Working Group, such as the names of the two working group chairs. This example table is implemented in the agent/mibgroup/examples/data_set.c file." ::= { netSnmpExampleTables 1 } netSnmpIETFWGEntry OBJECT-TYPE SYNTAX NetSnmpIETFWGEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "A row describing a given working group" INDEX { nsIETFWGName } ::= {netSnmpIETFWGTable 1 } NetSnmpIETFWGEntry ::= SEQUENCE { nsIETFWGName OCTET STRING, nsIETFWGChair1 OCTET STRING, nsIETFWGChair2 OCTET STRING } nsIETFWGName OBJECT-TYPE SYNTAX OCTET STRING (SIZE(1..32)) MAX-ACCESS not-accessible STATUS current DESCRIPTION "The name of the IETF Working Group this table describes." ::= { netSnmpIETFWGEntry 1 } nsIETFWGChair1 OBJECT-TYPE SYNTAX OCTET STRING MAX-ACCESS read-create STATUS current DESCRIPTION "One of the names of the chairs for the IETF working group." ::= { netSnmpIETFWGEntry 2 } nsIETFWGChair2 OBJECT-TYPE SYNTAX OCTET STRING MAX-ACCESS read-create STATUS current DESCRIPTION "The other name, if one exists, of the chairs for the IETF working group." ::= { netSnmpIETFWGEntry 3 } -- -- A table used in a table_iterator example -- (agent/mibgroup/examples/netSnmpHostsTable*.[ch]) -- netSnmpHostsTable OBJECT-TYPE SYNTAX SEQUENCE OF NetSnmpHostsEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "An example table that implements a wrapper around the /etc/hosts file on a machine using the iterator helper API." ::= { netSnmpExampleTables 2 } netSnmpHostsEntry OBJECT-TYPE SYNTAX NetSnmpHostsEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "A host name mapped to an ip address" INDEX { netSnmpHostName } ::= { netSnmpHostsTable 1 } NetSnmpHostsEntry ::= SEQUENCE { netSnmpHostName OCTET STRING, netSnmpHostAddressType InetAddressType, netSnmpHostAddress InetAddress, netSnmpHostStorage StorageType, netSnmpHostRowStatus RowStatus } netSnmpHostName OBJECT-TYPE SYNTAX OCTET STRING (SIZE(0..64)) MAX-ACCESS not-accessible STATUS current DESCRIPTION "A host name that exists in the /etc/hosts (unix) file." ::= { netSnmpHostsEntry 1 } netSnmpHostAddressType OBJECT-TYPE SYNTAX InetAddressType MAX-ACCESS read-create STATUS current DESCRIPTION "The address type of then given host." ::= { netSnmpHostsEntry 2 } netSnmpHostAddress OBJECT-TYPE SYNTAX InetAddress MAX-ACCESS read-create STATUS current DESCRIPTION "The address of then given host." ::= { netSnmpHostsEntry 3 } netSnmpHostStorage OBJECT-TYPE SYNTAX StorageType MAX-ACCESS read-create STATUS current DESCRIPTION "The storage type for this conceptual row." DEFVAL { nonVolatile } ::= { netSnmpHostsEntry 4 } netSnmpHostRowStatus OBJECT-TYPE SYNTAX RowStatus MAX-ACCESS read-create STATUS current DESCRIPTION "The status of this conceptual row." ::= { netSnmpHostsEntry 5 } -- -- Example Notifications -- netSnmpExampleHeartbeatRate OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS accessible-for-notify STATUS current DESCRIPTION "A simple integer object, to act as a payload for the netSnmpExampleHeartbeatNotification. The value has no real meaning, but is nominally the interval (in seconds) between successive heartbeat notifications." ::= { netSnmpExampleNotificationObjects 1 } netSnmpExampleHeartbeatName OBJECT-TYPE SYNTAX SnmpAdminString MAX-ACCESS accessible-for-notify STATUS current DESCRIPTION "A simple string object, to act as an optional payload for the netSnmpExampleHeartbeatNotification. This varbind is not part of the notification definition, so is optional and need not be included in the notification payload. The value has no real meaning, but the romantically inclined may take it to be the object of the sender's affection, and hence the cause of the heart beating faster." ::= { netSnmpExampleNotificationObjects 2 } netSnmpExampleHeartbeatNotification NOTIFICATION-TYPE OBJECTS { netSnmpExampleHeartbeatRate } STATUS current DESCRIPTION "An example notification, used to illustrate the definition and generation of trap and inform PDUs (including the use of both standard and additional varbinds in the notification payload). This notification will typically be sent every 30 seconds, using the code found in the example module agent/mibgroup/examples/notification.c" ::= { netSnmpExampleNotificationPrefix 1 } netSnmpExampleNotification OBJECT-TYPE SYNTAX SnmpAdminString MAX-ACCESS accessible-for-notify STATUS obsolete DESCRIPTION "This object was improperly defined for its original purpose, and should no longer be used." ::= { netSnmpExampleNotifications 1 } END
snmp常见命令：
snmpset, snmpget, snmptrap, snmpwalk, snmptest, snmptranslate.
snmpwalk -On: prints OID instead of name of keys.
