Specifications
69 / 80
See RFCs 1918 and 4193 for further information regarding private IP networks.
17.3. Introduction to IP address classes
In the modern IP-addressing, especially in public IP addresses, the classful addresses are not very
common. The lack of addresses in IP v.4 are causing the Internet service providers to switch to
classless addressing, where the netmasks are not fitting to the A, B or C classes, but instead used
to divide the classful addresses into smaller networks.
17.4. Classful IP-addressing
The historical division of network classes as A, B and C are described in the following table. The D
and E classes are omitted for the sake of clarity. The important thing in planning the IP network in
M2M solution is the number of hosts per network (see Table 7: Classful IP addresses below).
Class Netmask Size of network
Number bits
Size of host
Number bits
Number of
networks
Hosts per
network
A 255.0.0.0 8 24 128 16777214
B 255.255.0.0 16 16 16384 65534
C 255.255.255.0 24 8 2097152 254
• Table 7: Classful IP addresses
17.5. Classless IP-addressing
As can be seen in the table of classful private IP addressing, the smallest number of hosts per
network is 254 (class C). Sometimes, especially in Arctics' LANs, a smaller number of hosts would
be enough.
Note as well that the LAN addresses of the Arctic and M2M are chosen from private IP addresses.
The classful
notation of private IP address space is as follows in Table 8: Classful private IP
addresses below.
Class IP address range Netmask Size of
network
Number
bits
Size of host
Number bits
Number of
networks
Nr. of
addresses
A -
private
10.0.0.0 – 10.255.255.255 255.0.0.0 8 24 1 16777216
B -
private
172.16.0.0 – 172.31.255.255 255.255.0.0 16 16 16 1048576
C -
private
192.168.0.0 – 192.168.255.255 255.255.255.0 24 8 256 65536
• Table 8: Classful private IP addresses
When calculating the network size, it is commonly found that there is probably one or two Ethernet
connected devices behind each Arctic. Let's assume that we may need some room for future
expansion. Therefore, the suitable netmask would be 29-bit for leaving three IP addresses for
maintenance purposes or future use. See the Figure 66: Classless Arctic LAN below.