Exigo tool manual
Chapter 9
TCP/IP – network terms
35
IP configuration, a short summary
A complete IP configuration consists of the IP address of your computer, the subnet mask, the IP
address of the closest router (also called the
default gateway
) and a DNS server.
9.3 DHCP, fixed and dynamic addresses
Static and dynamic
The IP settings of a given piece of equipment can be manually configured, making it a so-called
static
IP address. It may also, upon starting up, be assigned an available IP address and additional IP settings
from a special computer, a so-called DHCP server, on the subnet. This is referred to as receiving a
dynamic
IP address.
Dynamic IP addresses
The use of dynamic addresses presents a problem when other equipments try to contact the equipment,
as the dynamic addresses are unknown in advance and are subject to change. To be able to contact
equipment using dynamic addresses, your equipment need to use DNS, which also has to be updated
when the dynamic address is changed via DHCP. This is commonly used in corporate networks and
for Windows computer. However, most Internet Service Providers and several types of EXO
controllers do not support the DNS update via DHCP, and must therefore use a static IP address.
9.4 White and black addresses
Black addresses
There is a shortage of IP addresses on the Internet and organizations are encouraged to use internal
IP addresses on internal networks. Different companies may use the same address series, as their
internal work computers never really need to connect directly to each other. This kind of addressing
is called
private
or
black
addressing.
Reserved addresses
The following addresses are reserved for private nets:
192.168.0.0 - 192.168.255.255
172.16.0.0 - 172.31.255.255
10.0.0.0 - 10.255.255.255
See also:
RFC1918, Address Allocation for Private Internets
[Online document], via
http://www.ietf.org/rfc/rfc1918.txt (last verified March 04, 2016).
White addresses
Addresses that are unique on the Internet are called public or
white
adresses. More information of the
use of IP addresses can be found in the document:
RFC3330, Special-use, IPv4 addresses
[Online
document], via http://www.ietf.org/rfc/rfc3330.txt (last verified March 04, 2016).
NAT
Firewalls can act as agents for computers with private IP addresses, when they are searching the
Internet for information. A connection from a computer with a black IP address is transformed into a
connection from the firewall (which has a public IP address) to the Internet server. The Internet server
may then return the information to the firewall which forwards it to the computer with the black
address. This is called
NAT
or
masquerading
.