2-1
2 RMON Configuration
Introduction to RMON
Remote monitoring (RMON) is a kind of management information base (MIB) defined by Internet
Engineering Task Force (IETF). It is an important enhancement made to MIB II standards. RMON is
mainly used to monitor the data traffic across a network segment or even the entire network, and is
currently a commonly used network management standard.
An RMON system comprises of two parts: the network management station (NMS) and the agents
running on network devices. RMON agents operate on network monitors or network probes to collect
and keep track of the statistics of the traffic across the network segments to which their ports connect,
such as the total number of the packets on a network segment in a specific period of time and the total
number of packets successfully sent to a specific host.
z RMON is fully based on SNMP architecture. It is compatible with the current SNMP
implementations.
z RMON enables SNMP to monitor remote network devices more effectively and actively, thus
providing a satisfactory means of monitoring remote subnets.
z With RMON implemented, the communication traffic between NMS and SNMP agents can be
reduced, thus facilitating the management of large-scale internetworks.
Working Mechanism of RMON
RMON allows multiple monitors. It can collect data in the following two ways:
z Using the dedicated RMON probes. When an RMON system operates in this way, the NMS directly
obtains management information from the RMON probes and controls the network resources. In
this case, all information in the RMON MIB can be obtained.
z Embedding RMON agents into network devices (such as routers, switches and hubs) directly to
make the latter capable of RMON probe functions. When an RMON system operates in this way,
the NMS collects network management information by exchanging information with the SNMP
agents using the basic SNMP commands. However, this way depends on device resources heavily
and an NMS operating in this way can only obtain the information about these four groups (instead
of all the information in the RMON MIB): alarm group, event group, history group, and statistics
group.
The device implements RMON in the second way. With an RMON agent embedded in, the device can
serve as a network device with the RMON probe function. Through the RMON-capable SNMP agents
running on the device, an NMS can obtain the information about the total traffic, error statistics and
performance statistics of the network segments to which the ports of the managed network devices are
connected. Thus, the NMS can further manage the networks.