8 SNMP
8.1 Introduction
The Watson Ethernet plug-in contains a built-in SNMP agent. The agent is ac-
cessible through the front-panel Q interface connector or through Ethernet in-
band management, either from an Ethernet user interface or over the DSL
Ethernet payload, cf. 3.5.
The agent uses standardized Management Information Bases (MIBs) to
represent the managed objects of the plug-in, its interfaces, the DSL spans and
the Ethernet bridging functions. All supported variables are listed in chapter 8.2.
The Watson Ethernet tabletop modem when connected as DSL slave to a Wat-
son Ethernet plug-in is manageable through the SNMP agent of the plug-in. The
tabletop modem is modeled with a vendor-specific MIB (Schmid Telecom HDSL
MIB, cf. 8.2.12).
If two Watson Ethernet plug-in modems are connected back to back then each is
managed by its own SNMP agent. In this situation the slave modem will normally
use Ethernet inband management.
8.1.1 AgentX
Several Watson Ethernet plug-in cards, installed in the same subrack, act as a
single SNMP agent towards the management system. The agents on the individ-
ual plug-ins cooperate to form one common data structure of the management
information available on each plug-in.
Within a subrack SNMP functions are divided between
a single processing entity called the master agent, which sends and receives
SNMP protocol messages in an agent role
several processing entities called subagents, which are "shielded" from the
SNMP protocol messages processed by the master agent, but which have
access to management information.
From the management systems point of view this combination of one master
agent and several subagents behaves exactly as would a single agent that has
access to the all management information within the subrack.
The communication between master agent and subagents uses the AgentX pro-
tocol which has been standardized as RFC 2741.
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