• Simple Network Management Protocol (SNMP) was created to monitor network devices.
• It is a protocol for monitoring and managing network devices. In addition, configuration tasks can be handled, and settings can be made remotely using this standard.
• SNMP also transmits control commands using agents over UDP port 161.
• SNMP lets a client (like a monitoring system) manage and configure devices by sending commands to them. Normally, in communication, the client asks the server for information. However, SNMP can also send "traps" — these are special messages sent from the server to the client automatically, without the client asking for them. These traps notify the client about important events or changes that happen on the server, like an error or a device malfunction. Traps are sent over a network using UDP port 162.

MIB

The Management Information Base (MIB) is a standardized guide that lists all the information and settings available on a device for SNMP. It organizes this information in a tree structure with unique identifiers (OIDs) for each item. MIB files don’t contain actual data but describe how to find and access it, including details like data types and permissions. This helps ensure compatibility between different devices and systems using SNMP.

OID

An OID (Object Identifier) is like an address in a hierarchy or tree structure. Each OID is a sequence of numbers, and the longer the sequence, the more specific the information it points to. Some nodes in the OID tree don’t hold any data themselves but just point to other nodes below them. OIDs are written as numbers separated by dots (e.g., 1.3.6.1.2). We can look up many MIBs for the associated OIDs in the Object Identifier Registry.

Default Configuration

• The default configuration of the SNMP daemon defines the basic settings for the service, which include the IP addresses, ports, MIB, OIDs, authentication, and community strings.

SNMP Daemon Config

cat /etc/snmp/snmpd.conf | grep -v "#" | sed -r '/^\\s*$/d'

Footprinting the Service

• For footprinting SNMP, we can use tools like snmpwalk, onesixtyone, and braa .
• Snmpwalk is used to query the OIDs with their information.