In networking, specifically within the context of the Simple Network Management Protocol (SNMP), OID stands for Object Identifier.
What is an OID?
An Object Identifier (OID) is a crucial component in network management systems, particularly those utilizing SNMP. As defined, an OID is an address used to uniquely identify managed devices and their statuses.
Think of it as a unique address or name for a specific piece of information or capability on a network device. This could be anything from the device's system name or location to the status of a network interface, CPU load, or memory usage.
OID in SNMP Context
The primary role of OIDs is to provide a standardized way for network management stations to communicate with managed devices (like routers, switches, servers, and printers) using SNMP.
- Identifying Objects: Devices managed by SNMP expose information and control points as "managed objects." Each of these objects is assigned a unique OID.
- Hierarchical Structure: OIDs are organized in a tree-like structure, similar to a file system path or a domain name. Each node in the tree is identified by a number, and the full OID is a sequence of numbers separated by dots, tracing a path from the root of the tree to the specific object.
- Management Information Base (MIB): The definitions and relationships of these managed objects and their corresponding OIDs are stored in Management Information Bases (MIBs). A MIB is essentially a database of OIDs that a device supports.
Structure of an OID
An OID path starts from a root defined by international standards organizations and branches out. Here’s a conceptual look at how an OID path might break down:
| Segment | Typical Path | Description |
|---|---|---|
| Root | 1 |
iso |
| Organization | 1.3 |
org |
| DOD | 1.3.6 |
dod |
| Internet | 1.3.6.1 |
internet |
| Private/Mgmt | 1.3.6.1.2 |
mgmt (Management) or 1.3.6.1.4 (Private) |
| MIB-2 | 1.3.6.1.2.1 |
mib-2 (Standard MIB for TCP/IP based internets) |
| System Group | 1.3.6.1.2.1.1 |
system group within MIB-2 |
| Specific Object | 1.3.6.1.2.1.1.1 |
sysDescr (Description of the system) |
Each number in the sequence corresponds to a node in the OID tree. Following the sequence leads directly to the specific piece of data or control function on the device that the OID represents.
Practical Use
In practice, OIDs are used by network monitoring tools and scripts:
- To query devices for specific information (e.g., "What is the value of OID
1.3.6.1.2.1.1.1on device X?" which returns the system description). - To set configuration parameters on devices (if the object is writable).
- To receive traps (alerts) from devices, which include OIDs indicating the event that occurred.
Understanding OIDs is fundamental for anyone working with SNMP-based network management and monitoring systems, as they are the universal language used to identify and interact with manageable resources on a network.
