A MIB is a hierarchical database of objects and their values, stored in an SNMP agent.
Generally, the objects of the MIB are referenced by an identifier. For example, the internet object is referred to by 1.3.6.1, or iso-ccitt.identified-organization.dod.internet.
Through the MIB, you have access to the information for management, which is contained in the internal memory of the device in question. MIB is a complete and well-defined database, with a tree structure, and is suitable for handling various groups of objects, with unique identifiers for each object.
The SNMP architecture operates with a small group of objects that are defined in detail in the RFC 1066 Management information base for network management over TCP/IP.
The 8 groups of objects that are usually handled by MIB, which define a total of 114 objects (recently, with the introduction of MIB-II, are defined up to a total of 185 objects), are as follows:
- System: Includes the identity of the vendor and the time since the last reinitialization of the management system
- Interfaces: Single or multiple interfaces, local or remote
- ATT (Address Translation Table): Contains the address of the network and the equivalences with the physical addresses
- IP (Internet Protocol): Provides the route tables, and keeps statistics on the received IP datagrams
- ICMP (Internet Communication Management Protocol): Counts the number of received ICMP messages and errors
- TCP (Transmission Control Protocol): Provides information about TCP connections and retransmissions
- UDP (User Datagram Protocol): Counts the number of UDP datagrams sent, received, and delivered
- EGP (Exterior Gateway Protocol): Collects information on the number of EGP messages that are received and generated
SNMP is a client/server-based network protocol. The server daemon provides the requested information to the clients. If you are working with a Debian-based distribution, you can install snmp in your local machine with the apt-get install snmp command. This will provide some snmp commands. In your machine, if SNMP has been installed and configured properly, you can use the snmpwalk utility command to query the basic system information by using the following syntax:
# snmpwalk -v2c -c public localhost
Here is the output of the execution of the snmpwalk command, where we can see information being returned by the SNMP agent:
iso.3.6.1.2.1.1.1.0 = STRING: "Linux debian6box 2.6.32-5-686 #1 SMP
Tue Jan 15 15:00:01 UTC 2019 i686"
iso.3.6.1.2.1.1.2.0 = OID: iso.3.6.1.4.1.8072.3.2.10
iso.3.6.1.2.1.1.3.0 = Timeticks: (88855240) 10 days, 6:49:12.40
iso.3.6.1.2.1.1.4.0 = STRING: "Me <[email protected]>"
iso.3.6.1.2.1.1.5.0 = STRING: "debian6box"
iso.3.6.1.2.1.1.6.0 = STRING: "Sitting on the Dock of the Bay"
The output of the preceding command will show the MIB number and its values. For example, the iso.3.6.1.2.1.1.1.0 MIB number shows that it's a string type value, such as Linux debian6box 2.6.32-5-686 #1 SMP Tue Jan 15 15:00:01 UTC 2019 i686.