Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 1766)

SNMP Introduction
Software Reference for x310 Series Switches
67.8 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
The SNMP Protocol
The SNMP protocol provides a mechanism for management entities, or stations, to extract
information from the Management Information Base (MIB) of a managed device.
The normal method of accessing information in a MIB is to use a Network Management
Station (NMS), typically a PC or workstation, to send commands to the managed device (in
this case the switch) using the SNMP protocol.
SNMP can use a number of different protocols as its underlying transport mechanism, but
the most common transport protocol, and the only one supported by the switch, is UDP.
Therefore the IP module must be enabled and properly configured in order to use SNMP.
SNMP trap messages are sent to UDP port 162; all other SNMP messages are sent to UDP
port 161. The switch’s SNMP agent accepts SNMP messages up to the maximum UDP
length the switch can receive.
Other transport mappings have been defined (e.g. OSI [RFC 1418], AppleTalk [RFC 1419]
and IPX [RFC 1420]), but the standard transport mapping for the Internet (and the one the
switch uses) is UDP. The IP module must be enabled and configured correctly. See
Chapter 25, IP Addressing and Protocol Commands for detailed descriptions of the
commands required to enable and configure IP.
SNMP Versions
The switch supports SNMP version 1 (SNMPv1), SNMP version 2c (SNMPv2c) and SNMP
Version 3 (SNMPv3). The three versions operate similarly.
SNMPv2c updated the original protocol, and offered the following main enhancements:
■ a new format for trap messages.
■ the get-bulk-request PDU allows for the retrieval of large amounts of data, including
tables, with one message.
■ more error codes mean that error responses to set messages have more detail than is
possible with SNMPv1.
■ three new exceptions to errors can be returned for get, get-next and get-bulk-request
messages. These are: noSuchObject, noSuchInstance, and endOfMibView.
SNMPv3 provides significant enhancements to address the security weaknesses existing
in the earlier versions. This is achieved by implementing two new major features:
■ Authentication - by using password hashing and time stamping.
■ Privacy - by using message encryption.
Support for multiple versions of SNMP is achieved by responding to each SNMP request
with a response of the same version. For example, if an SNMPv1 request is sent to the
switch, an SNMPv1 response is returned. If an SNMPv2c request is sent, an SNMPv2c
response is returned. Therefore, authentication and encryption functions are not invoked
when messages are detected as having either an SNMPv1 or SNMPv2c protocol format.