NetSNMP开源代码学习——小试牛刀

原创作品，转载请注明出处，严禁非法转载。如有错误，请留言！

email：40879506@qq.com

题外话：技术越是古董级的东西，越是值得学习。

一. 配置

参考: http://www.cnblogs.com/oloroso/p/4595123.html

./configure --prefix=/usr/local/net-snmp --with-default-snmp-version=2c --with-sys-contact="xxx@163.com" --with-sys-location="China" --with-logfile="/var/log/snmpd.log" --with-persistent-directory=/var/net-snmp/ --enable-applications --enable-ipv6 --with-out-transports="TCP TCPv6 Unix" --with-transports="Callback UDP UDPIPv6"  --disable-nls --enable-shared --enable-static --disable-embedded-perl

最后输出配置简要如下，说明配置成功。如果遇到缺少perl之类的库错误，说明需要安装依赖库，常用命令是suod apt-get install libxxx-dev或者xxx-dev或者libxxx

---------------------------------------------------------
            Net-SNMP configuration summary:
---------------------------------------------------------

SNMP Versions Supported:    1 2c 3
  Net-SNMP Version:           5.4.4
  Building for:               linux
  Network transport support:  TCPIPv6 Callback UDP UDPIPv6
  SNMPv3 Security Modules:     usm
  Agent MIB code:             default_modules =>  snmpv3mibs mibII ucd_snmp notification notification-log-mib target agent_mibs agentx disman/event disman/schedule utilities host
  Embedded Perl support:      disabled
  SNMP Perl modules:          building -- not embeddable
  SNMP Python modules:        disabled
  Authentication support:     MD5 SHA1
  Encryption support:         DES AES

二. 安装

make && make install

三. 设置环境变量

添加如下一行
# vi /etc/profile
PATH=/usr/local/net-snmp/bin:/usr/local/net-snmp/sbin:$PATH
source  /etc/profile

四. 配置文件

参考 ：http://www.cnblogs.com/oloroso/p/4844907.html
以SNMPv2为例
rocommunity             public
rwcommunity             private

五.运行和测试SNMP V2

运行：
snmpd -c /usr/local/net-snmp/share/snmp/snmpd.conf
测试：
root@andy:/home/andy/vm_share/netsnmp/net-snmp-5.4.4# snmpget -v 2c -c public 127.0.0.1 system.sysName.0    
SNMPv2-MIB::sysName.0 = STRING: andy
snmpwalk -v 2c -c public 127.0.0.1 system

六.配置文件内容

参考：以V2为例, 增加一些高级内容，VACM理论可以参考官方文档。这里等以后学习了，再专门分析一下，基于视图的访问控制模型还是值得学习一下，网上也有很多文章滴。

 syslocation suzhou_SIP
 syscontact localhost
 sysname gateway
 iquerySecName root

 com2sec public 0.0.0.0 public
 com2sec private 0.0.0.0 private
 group public v1 public
 group private v1 private
 group public v2c public
 group private v2c private

 view all included .
 access public "" v2c noauth exact all none all
 access private "" v2c noauth exact none all all

七.遇到问题
错误：
SNMPv3 report received from remote agent.
Security user name: yy
Security engine ID: 80.00.1F.88.80.3C.89.93.24.CB.C3.B3.58 (hex)
Context name: (zero-length)
Context engine ID: 80.00.1F.88.80.3C.89.93.24.CB.C3.B3.58 (hex)
Authentication protocol: HMAC SHA
Privacy protocol: CFB AES 128
Security level: Authentication And Privacy
Security model: USM
1: usmStatsWrongDigests.0 (counter) 1
原因：认证和加密值不符合要求

 Name:    usmStatsWrongDigests
 Type:    OBJECT-TYPE
 OID:    1.3.6.1.6.3.15.1.1.5
 Full path:    iso().org().dod().internet().snmpV2().snmpModules().snmpUsmMIB().usmMIBObjects().usmStats().usmStatsWrongDigests()
 Module:    SNMP-USER-BASED-SM-MIB

 Parent:    usmStats
 Prev sibling:    usmStatsUnknownEngineIDs
 Next sibling:    usmStatsDecryptionErrors

 Numerical syntax:    Counter ( bit)
 Base syntax:    Counter32
 Composed syntax:    Counter32
 Status:    current
 Max access:    read-only

 Description:    The total number of packets received by the SNMP
      engine which were dropped because they didn't
      contain the expected digest value.

解决办法：
检查认证值和加密值长度是否符合最低要求。或者修改usmStatsWrongDigests里面的函数检查。

八.参考

http://www.cnblogs.com/oloroso/p/4844907.html
http://www.net-snmp.org/wiki/index.php/Tutorials