USER’S GUIDE
354 CyberSWITCH
The SNMP Agent will process all SNMP Protocol Data Units (PDUs) which are received at a LAN
port or which are received at a WAN port. (A PDU contains both data and control (protocol)
information that allows the two processes to coordinate their interactions. The SNMP feature has
five types of PDUs: GetRequests, GetNextRequests, GetResponses, SetRequests, and Traps.) This is
shown in the above illustration, which depicts a network in which the Network Management
Station on LAN A or the remote NMS can manage the system.
All SNMP GetRequest, GetNextRequest, and SetRequest PDUs will be parsed and processed by the
SNMP Agent, and an appropriate GetResponse PDU will be generated in response to each valid
request PDU. In addition, to ensure security, each incoming PDU will be authenticated by the
SNMP Agent. The authentication scheme makes use of a table of Community Name/MIB-access-
level pairs, which is searched to determine if the Community Name specified in an incoming
request PDU is valid. If the Community Name is valid, the corresponding MIB access level is then
checked to determine if the Community Name has the access rights needed to perform the desired
PDU action. If either the Community Name or the MIB access right level is invalid, the SNMP
Agent will discard the request PDU.
The collection of data objects that can be managed using the GetRequest, GetNextRequest, and
SetRequest PDUs is known as the Management Information Base (MIB). The MIB maintained by
the SNMP Agent consists of a universal standard set of objects, known as MIB-2, as well as a set of
objects that are specific to the system, known as the Enterprise MIB.
The definition for MIB-2 is given in RFC (Request For Comments) 1213: “Management Information
Base for Network Management of TCP/IP-based Internets: MIB-II.”
The SNMP Agent supports the following MIB-2 groups: the System group, the Interfaces group, the
Address Translation (AT) group, the Internet Protocol (IP) group, the Internet Control Message
MIB Formatter
ASN. 1 File
WAN
MIB
MIB
Network Management
Station
Network Management
Station
128.111.1.1
LAN A
128.111.1.1
CSX5500
