Chapter 3 Ethernet Communications Overview
MiniCapt Remote Microbial Air Sampler Operations Manual
Page 3-3
Gateway Address
The gateway address is a special address used to allow communications outside of the
local network. In the telephone analogy, it allows placing long distance calls. In many
(if not most) situations, a gateway address is not required.
The default gateway address set when restoring defaults to a Particle Measuring
Systems instrument is
10.255.0.60
. This address should be cleared or set to whatever
is required by IT.
Multicast Address
The multicast address is used by Facility Net to query all instruments attached to a
local network. The valid multicast address range is defined as
224.0.0.0
to
239.255.255.255
. From a practical standpoint addresses in the
224.0.X.X
range
should not be used as many of them are reserved for other communications.
Particle Measuring Systems assigns a factory default multicast address of
224.100.100.1
to all instruments. This address generally does not need to be changed.
The exception is when sensors are integrated into a large network. In this situation, IT
may recommend an alternative multicast address to avoid network conflicts.
MAC Address
All Ethernet devices have a MAC (Media Access Control) address. This address may be
thought of as an Ethernet serial number. It is unique for all devices. If an instrument
needs to be replaced with a different instrument for either calibration or service, the
service technician will duplicate the old instrument’s IP address into the new
instrument. However, the MAC address of the new instrument will be unique.
In Particle Measuring Systems instruments the MAC address is set during production.
The value is permanently stored in non-volatile memory on the main processor circuit
board. (The MAC address will change if the main circuit board is replaced.) The MAC
address may be displayed via the HyperTerminal
®
(i.e., RS-232 service interface) by
using the
status
command.
Routers and switches keep track of which MAC address is attached where. For that
reason, it is important for the instrument to tell a router or switch who is attached. For
all Particle Measuring Systems instruments, this is done at least once when the
instrument boots. In some newer instruments, the MAC address is announced to the
switch or router every time a network connection is detected. Without this
mechanism, it would be possible for routers to operate for an extended period of time
without recognizing which MAC address is mapped to which IP address.
