Chapter 13. Network Administration
242
PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual
GFK-2224Q
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
Class
0 – 126
A
127
Loopback
128 - 191
B
192 - 223
C
224 - 239
D (Reserved for Multicast Use)
240 - 255
E (Reserved for Experimental Use)
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
(Class A)
172.16.0.0 – 172.31.255.255
(Class B)
192.168.0.0 – 192.168.255.255
(Class C)
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:
Summary of Contents for PACSystems RX7i
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