SNMP (Simple Network Management Protocol) is a Layer-7 protocol for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior. It allows devices to communicate even if the devices are different hardware and run different software.
There are two major types of devices in SNMP, they are Managed devices which are devices being managed using SNMP and Network Management Station (NMS) which could be a device or devices managing the managed devices. It could also be seen as the SNMP server.
SNMP is a Layer7 protocol (Application Layer), with a defined standard of RFC1155, RFC1157. The purpose of SNMP is for network management and has three main versions (SNMPv1, SNMPv2c, SNMPv3). SNMP agent receives requests/responses on UDP port 161, and notifications on port 162.
There are three basic operations that are used in SNMP:
- Managed devices can alert the NMS events
- NMS can ask the managed devices for info about their present state
- NMS can inform the managed devices to modify aspects of their configuration
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https://www.dpstele.com/snmp/v1-v2c-v3-difference.php
SNMPv1
SNMPv1 is the first version of SNMP. It's easy to set up, as it only requires a plain text community.
Although it accomplished its goal of being an open, standard protocol, it was found to be lacking in key areas for certain managing applications. For example, it only supports 32-bit counters and has poor security features - a community string is the only security method in the SNMPv1.
Later versions have addressed many of these problems. Smaller RTUs commonly support SNMPv1.
Later versions have addressed many of these problems. Smaller RTUs commonly support SNMPv1.
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SNMPv2c
The Get, GetNext, and Set operations used in SNMPv1 are identical as those used in SNMPv2c. However, SNMPv2c's key advantage over previous versions is the Inform command. Unlike Traps, which are simply received by a manager, Informs are positively acknowledged with a response message. If a manager does not reply to an Inform, the SNMP agent will resend the Inform.
Other advantages include:
- Improved error handling
- Improved SET commands
SNMPv2 security, just like for SNMPv1, comes into the form of community strings. This is a password that your devices will need to able allowed to talk to each other and transfer information when SNMP requests occur.
Also, keep in mind that not all devices are SNMPv2c compliant, so your SNMP manager should be downward compatible with SNMPv1 devices. You can also use an SNMPv3 mediation device to ensure compatibility with earlier versions.
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SNMPv3