Ip Addresses Reserved For Private Networks; Multicast Ip Addresses; Loopback Ip Addresses; Overlapping Subnets - GE RX3i User Manual

Chapter 13. Network Administration
To determine the class of an IP address, examine the first integer in its dotted-decimal IP address and compare
it with the range of values in the following table.
Range of first integer
0 – 126
127
128 - 191
192 - 223
224 - 239
240 - 255

IP Addresses Reserved for Private Networks

RFC 1918 reserves IP addresses in the following ranges to be used for private networks.
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255

Multicast IP Addresses

Multicast IP Addresses are used in multicasting, a technique that allows delivery of a single packet of data to
multiple nodes on the network. Any node that joins a Multicast group will respond to the Multicast IP address
assigned to that group. Subsequently, any data sent to that Multicast IP address may be received by all nodes
that are members of that Multicast group. Multicast (Class D) IP addresses (224.0.0.0 through 239.255.255.255)
are reserved by the Internet authorities for multicasting.
Multicasting is a feature of Ethernet Global Data. For more information on the use of multicasting in Ethernet
Global Data, see Chapter 5.

Loopback IP Addresses

Class A IP Addresses in the 127.xxx.xxx.xxx range are reserved for loopback addressing. A network packet using
a loopback destination address is not actually transmitted on the network, but instead is processed by the
same device as if it were received from the network.
PACSystems Ethernet interfaces recognize only the IP address 127.0.0.1 as a loopback address. All other
addresses in the range 127.0.0.2 – 127.255.255.255 are ignored and do not provide loopback operation.

Overlapping Subnets

Each interface on a LAN must have a unique IP Address and a non-overlapping IP subnet. This is configured in
PME. Care must be taken to survey the entire connected network architecture in order to tabulate the IP
addresses and IP subnets already in use, both on the local networks and on any of its routed subnets
connected with a gateway. Never assign a conflicting IP Address or configure duplicate IP subnets.
The following examples would be problematic:
242 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual
Class
A
Loopback
B
C
D (Reserved for Multicast Use)
E (Reserved for Experimental Use)
(Class A)
(Class B)
(Class C)
GFK-2224Q