User manual
58
Remote control
possesses a private IP address (LAN IP address) and also a
public IP address (WAN IP address), via the Internet.
If network elements exchange data only over a local net-
work (without connection with the Internet), appropriate
use private IP addresses. Select in addition e.g. a private IP
address for the instrument and a private IP address for the
host (PC), with which you would like to control the instru-
ment. If you might connect your private network with the
Internet later via a router, the private IP addresses used in
your local network can be maintained. Since within each
IPaddressrangetherstIPaddressisusedasnetwork
IP address and the last IP address is used as Broadcast IP
address, in each case two IP addresses have to be taken
off from the “number of possible host addresses“ (see ta-
ble 1: Private IP address ranges). Apart from the organiza-
tion of IP addresses into public and private address ranges,
IP addresses are also divided into classes (Class: A, B, C,
D, E). Within the classes A, B, and C are also include the
private IP of address ranges described before. The catego-
risation from IP addresses is for the assignment of public
IP address ranges of importance and essentially depends
on the size of a local network (maximum number of hosts
in the network), which is to be connected with the Internet
(seetable2:ClassesofIPaddresses).IPaddressescanx
(statically) or variable (dynamically) to be assigned.
IfIPaddressesinanetworkareassignedx,anIPaddress
must be preset manually with each network element. If IP
addresses in a network are assigned to the attached net-
work elements automatically (dynamically), a DHCP server
(EnglishDHCPbecomes;DynamicHostConguration
Protocol) is required for the dispatching of IP addresses.
With a DHCP server an IP address range for the automatic
dispatching of IP addres ses can be preset. A DHCP server
is usually already integrated in a router (DSL router, ISDN
router, Modem router, WLAN router, …) integrated. If a
network element (e.g. an instrument) is connected by a
network cable directly with a host (PC), the IP addresses
cannot be assigned to the instrument and the host (PC) au-
tomatically, since no network with DHCP server is present
here. They have to be preset therefore at the instrument
and at the host (PC) manually.
IP addresses are divided by using subnet mask into a
network quota and into a host quota, so similarly e.g. a
telephone number is divided in pre selection (land and lo-
cal area network number) and call number (user number).
Subnet mask have the same form as IP addresses. They
are represented with four decimal numbers separated
by points (e.g. 255.255.255.0). As is the case for the IP
addresses here each decimal number represents a binary
number of 8 bits. The separation between network quota
and host quota is determined by the subnet mask within
an IP address (e.g. the IP address 192.168.10.10 by the sub-
net mask 255.255.255.0 is divided into a network quota
192.168.10.0 and a host quota of 0.0.0.10). The allocation
takes place via the transformation of the IP address and
the subnet mask in binary form and afterwards a bit by bit
one logical AND operation between IP address and subnet
mask. The result is the network quota of the IP address.
The host quota of the IP address takes place via the bit by
bit logical NAND operation between IP address and subnet
mask. By the variable allocation of IP addresses in network
quota and host quota via subnet masks, one can specify IP
address ranges individually for large and small networks.
Thus one can operate large and small IP networks and
connect if necessary to the Internet via a router. In smaller
local networks the subnet mask 255.255.255.0 is mostly
used.Networkquota(therst3numbers)andhostquota
(the last number) are simple here without much mathe-
matical expenditure to determine and it can with these
subnet mask up to 254 network elements (e.g. measuring
instruments, hosts/PC‘s...) in a network be operated at the
same time.
Often also a standard gateway is present in a network. In
most local networks is this gateway with the router to the
Internet (DSL router, ISDN router etc.) is identical. Using
this (gateway -) router a connection can be manufactured
with another network. Thus also network elements, which
are not in the same (local) network, can be reached and/
or network elements from the local network are able to ex-
change data with network elements from other networks.
For a network-spreading data exchange the IP address of
the standard gateway must also be preset. In local net-
works,mostlytherstIPaddresswithinanetworkforthis
class adress range net quota host quota max. number of networks max. number of hosts
A 0.0.0.1 - 127.255.255.255 8 Bit 24 Bit 126 16.777.214
B 128.0.0.1 - 191.255.255.255 16 Bit 16 Bit 16.384 65.534
C 192.0.0.1 - 223.255.255.255 24 Bit 8 Bit 2.097.151 254
D 224.0.0.1 - 239.255.255.255 Reserved for multicast applications
E 240.0.0.1 - 255.255.255.255 Reserved for special applications
Table 13.2: Classes of IP adresses
adress range subnetz mask CIDR way of writing number of possible host adresses
10.0.0.0 –10.255.255.255 255.0.0.0 10.0.0.0/8 2
24
−2=16.777.214
172.16.0.0 –172.31.255.255 255.240.0.0 172.16.0.0/12 2
20
−2=1.048.574
192.168.0.0 –192.168.255.255 255.255.0.0
255.255.255.0
192.168.0.0/16
192.168.0.0/24
2
16
−2=65.534
2
8
−2=254
Table 13.1: Private IP adress ranges