Installation manual

57 ATTO Technology Inc. ATTO Utilities Installation and Operation Manual
SubAgent Mode
This mode of operation relies on the operating
system's SNMP service being installed as a Master
Agent and running. All Management Station requests
must be directed to this Master Agent,
not the ATTO
agent. It is expected that only experienced SNMP
administrators will use this mode, as installing and
configuring the operating system services are beyond
the scope of this document. Examples are Windows
SNMP services, or the open-source Net-SNMP
package.
In this mode, the system service is automatically
reconfigured so that when the service receives
requests for the ATTO branch of the OID tree, the
request is delegated to the ATTO agent through the
loopback interface on a different port. While the
primary benefit of subagent mode is to allow the
Master Agent to handle most requests directly (the
operating system services implement many more
MIBs than the ATTO agent), and to allow multiple
subagents to be merged into a single OID tree, this
mode can be used to enable features that are not
supported by the ATTO agent.
For example, if the system service supports version 3
of the protocol, all communication over the network
between the Management Station and the service can
be encrypted using the desired privacy options of
version 3. The system service will then communicate
to the ATTO agent using one of the supported
protocols.
Note
For security purposes, the ATTO agent will
only respond to requests through the
loopback interface when in subagent mode.
If the system service is stopped, the ATTO
agent will be inaccessible from any other
host on the network.
Note
Other features that are not directly supported
by the ATTO agent, but can be enabled with
this configuration include source address
filtering and stronger authentication than
simple community strings provide. All of
these features depend on properly
configuring the system service, and are
beyond the control of the ATTO agent. Refer
to the documentation for the system service
to determine how to enable these features.
Note
On Windows Vista Service Pack 1 and
Windows 2008, a bug in the Microsoft SNMP
service prevents subagent mode from
working correctly. This is a known issue that
requires a hotfix:
http://support.microsoft.com/kb/950923. The
bug has been fixed in service pack 2.
Enabled mode is not affected, nor is the
Net-SNMP service if that is being used as
a replacement for the Microsoft service.
Note
The Net-SNMP service that ships with Mac
OS X 10.4 lacks the functionality needed to
support subagent mode. To work around
this, you need to use the enabled mode or
build the Net-SNMP package from source
with proxy support enabled.