SNMP (Simple Network Management Protocol)

 

Simple Network Management Protoco——SNMP（ Simple network management protocol ）

In the current increasingly complex network environment , There are various network devices in the whole environment , In order to better manage these devices , Early detection of existing or future problems in the network ,SNMP It provides a technical basis for effective management of these network devices .

SNMP By IETF（Internet Engineeriing Task Force, Internet Engineering Task Force ） The set of definitions is based on SGMP（Simple Gateway Monitor Protocol, Simple Gateway Monitoring Protocol ） Network management protocol . With SNMP Network management system for Technology （NMS） in , Manage host utilization SNMP Conduct remote monitoring and management of all devices supporting this protocol on the network ( Such as computer workstation 、 terminal 、 Router 、Hub、 Network printer, etc ), Mainly responsible for monitoring equipment status 、 Modify the device configuration 、 Accept the event warning, etc

SNMP It mainly works between the management host and network equipment .

Some basic concepts

Manager： Installed SNMP Host of management software

Managed Device： Managed network devices （ Including computers 、 Router 、 Switches and so on ）

Agent： On network devices SNMP Management system （ You can simply say Managed Device Namely Agent）

MIB（Management Information Base）： Used to save all kinds of OID The database of

OID（Object Identifies）： Used to describe all kinds of information about network devices （ event ）, such as ：CPU Utilization ratio 、 Interface status 、 Routing table, etc

MIB Divided into criteria MIB And private MIB, standard MIB Applicable to all network devices , And private MIB The equipment manufacturer shall define by itself after applying to relevant institutions .MIB Tree structure , Each node is assigned a string and a small integer as labels , namely OID(Object Identifier)

MIB The name of any object in the structure tree is the label sequence of each node on the path from the root to the object node , The labels are separated by dots . For example, for each network interface in the managed device IP The address information is expressed as ：iso.org.dod.internet.mgmt.mid.ip, Its number is expressed as ：1.3.6.1.2.1.4. 

standard MIB Basic OID think 1.3.6.1.2.1 Prefix , And private MIB Basic OID think 1.3.6.1.4.1 Prefix . If there are multiple messages under a certain node , Exists in a list , such as IP The address information includes the subnet mask 、 Gateway address, etc .

SNMP There are five message types ：

1. Get_Request：Manager To the end Agent The client sends a request to read information ; 

2. Get_Next_Request：Manager To the end Agent The client sends a request to read information ; 

3. Set_Request：Manager To the end Agent End sending device setting information ,Agent The terminal can change the device state according to the setting information ; 

4. Get_Response：Agent End to Manager Response to end request ; 

5. Trap： When Agent When something happens on the end ,Agent Take the initiative to Manager Send trap information at the end , Such as shutdown events .

Two kinds of Community：

RO： read-only —— Only those sent by network devices can be received trap news

RW： Reading and writing —— It can receive messages sent by network devices trap news , It can also modify the configuration of network devices

Community It is like a clear password to match between the manager and the managed ;

for example ：

Suppose there is... Between the manager and the managed Community yes CCIE;

When the manager receives trap First detect Community Fields follow CCIE Is it consistent 、 Receive only when it is consistent, otherwise discard ！

To configure SNMP：

Switch(config)# access-list 10 permit 10.1.1.0 0.0.0.255

Switch(config)# snmp-server community wisdom RO 10

Switch(config)# snmp-server community xmws RW 10

Switch(config)# snmp-server enable trap

Switch(config)# snmp-server host 10.1.1.100 xmws