Page 3-2
MiniCapt Remote Microbial Air Sampler Operations Manual
Chapter 3 Ethernet Communications Overview
In the analogy of a telephone number, there is an area code and a phone number.
Unlike a telephone number, the network (or area code) portion of an IP address can be
set to different numbers of digits. It is not a fixed size like an area code. The location
portion is the rest of the number – everything that is not part of the network portion.
The definition of what is network and what is location is done by the network mask,
described below.
Although there are a great many numbers in the range of 0.0.0.0 to 255.255.255.255, in
almost all circumstances instruments are placed on a segregated private network that
uses a greatly reduced set of numbers. The valid ranges are shown in
.
Table 3-1
Private IPv4 Network Ranges
Address Class
Start
End
A (24 Bit Range)
10.0.0.0
10.255.255.255
B (20 Bit Range)
172.16.0.0
172.31.255.255
C (16 Bit Range)
192.168.0.0
192.168.255.255
Particle Measuring Systems provides a unique default address in the Class A range for
every instrument. Whenever the instrument is set to default parameters or factory
defaults, this address is restored.
Network Mask
The network mask is used to discern the network portion of the IP address from the
location portion. From a telephone number analogy, it segregates the area code from
the phone number. It is easy to set the mask incorrectly, and when it is incorrect, it can
result in sporadic communication problems. For example, in Facility Net an
instrument can be seen as available via a Multicast probe, but trying to control the
instrument causes a communications error.
The mask is actually a 32 bit binary number consisting of some number of 1’s followed
by enough 0’s to make 32 bits. The length of the 1’s depends on the network Address
Class (i.e., area code size) as well as sub-netting (i.e., something done by IT).
shows the default network mask for each address class.
Table 3-2
Default Network Mask Values
Address Class
Default Network Mask
A (24 Bit Range)
(e.g., 10.X.X.X)
255.0.0.0
B (20 Bit Range)
(e.g., 172.16.X.X)
255.240.0.0
C (16 Bit Range)
(e.g., 192.168.X.X)
255.255.0.0
When a Particle Measuring Systems instrument is set to default parameter or factory
defaults, the network mask is set to
255.0.0.0
. This corresponds with the
10.X.X.X
address which is also set.
For large systems, IT personnel will dictate a network mask value and the value may
be different from what is shown in the table. Make sure the network mask is set as
specified by IT. All PCs, routers and instruments on a network must use exactly the
same network mask, or communication problems will arise.
