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DGS-1520 Series Gigabit Ethernet Smart Managed Switch Web UI Reference Guide
39
SNMP
Simple Network Management Protocol (SNMP) is an OSI Layer 7 (Application Layer) designed specifically for
managing and monitoring network devices. SNMP enables network management stations to read and modify the
settings of gateways, routers, switches, and other network devices. Use SNMP to configure system features, monitor
performance, and detect potential problems with the Switch, switch group, or network.
Managed devices that support SNMP include software (referred to as an agent) which runs locally on the device. A
defined set of variables (managed objects) is maintained by the SNMP agent and used to manage the device. These
objects are defined in a Management Information Base (MIB), which provides a standard presentation of the
information controlled by the on-board SNMP agent. SNMP defines both the format of the MIB specifications and the
protocol used to access this information over the network.
The Switch supports the SNMP versions 1, 2c, and 3. The three versions of SNMP vary in the level of security
provided between the management station and the network device.
In SNMPv1 and SNMPv2c, user authentication is accomplished using 'community strings', which function like
passwords. The remote user SNMP application and the Switch SNMP must use the same community string. SNMP
packets from any station that has not been authenticated are ignored (dropped). The default community strings for the
Switch used for SNMPv1 and SNMPv2c management access are:
• public - Allows authorized management stations to retrieve MIB objects.
• private - Allows authorized management stations to retrieve and modify MIB objects.
The SNMPv3 protocol uses a more sophisticated authentication process that is separated into two parts. The first part
maintains a list of users and their attributes that are allowed to act as SNMP managers. The second part describes
what each user in that list can do as an SNMP manager. The SNMPv3 protocol also provides an additional layer of
security that can be used to encrypt SNMP messages.
The Switch allows groups of users to be listed and configured with a shared set of privileges. The SNMP version may
also be set for a listed group of SNMP managers. Thus, you may create a group of SNMP managers that are allowed
to view read-only information or receive traps using SNMPv1 while assigning a higher level of security to another
group, granting read/write privileges using SNMPv3.
Using SNMPv3, users or groups can be allowed or be prevented from performing specific SNMP management
functions. These are defined using the Object Identifier (OID) associated with a specific MIB.
MIBs
A Management Information Base (MIB) stores management and counter information. The Switch uses the standard
MIB-II Management Information Base module, and so values for MIB objects can be retrieved using any SNMP-based
network management software. In addition to the standard MIB-II, the Switch also supports its own proprietary
enterprise MIB as an extended Management Information Base. Specifying the MIB Object Identifier may also retrieve
the proprietary MIB. MIB values can be either read-only or read-write.
The Switch incorporates a flexible SNMP management system, which can be customized to suit the needs of the
networks and the preferences of the network administrator. The three versions of SNMP vary in the level of security
provided between the management station and the network device. SNMP settings are configured using the menus
located in the SNMP folder of the Web UI.
Traps
Traps are messages that alert network personnel of events that occur on the Switch. The events can be as serious as
a reboot (someone accidentally turned the Switch off/unplugged the Switch), or less serious like a port status change.
The Switch generates traps and sends them to the trap recipient (or network manager). Typical traps include trap
messages for Authentication Failure, Topology Change, and Broadcast/Multicast Storm.
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