How can I know my IP scheme

Create an IPv4 addressing scheme

Note -

For information about planning IPv6 addresses, see Preparing an IPv6 Addressing Plan.

This section provides a general introduction to IPv4 addressing to help you create an IPv4 addressing plan. For more information about IPv6 addresses, see Introduction to IPv6 Addressing. For more information on DHCP addresses, see Chapter 12, Introducing Oracle Solaris DHCP.

Every IPv4-based network must have the following:

  • A unique network number assigned either by an ISP or an IR, or - for older networks - registered by the IANA. If you want to use private addresses, the network numbers you use must be unique within your company.

  • Unique IPv4 addresses for the interfaces of each system on the network.

  • A network mask.

An IPv4 address is a 32-bit address that uniquely identifies a network interface in a system. This is detailed in Applying IP Addresses to Network Interfaces. An IPv4 address is written in decimal numbers, divided into four 8-bit fields separated by periods. Each 8-bit field represents one byte of the IPv4 address. This format of representing the bytes of an IPv4 address is also called separate decimal notation designated.

The following figure shows the components of the IPv4 address.

Figure 2–1 IPv4 address format

Registered IPv4 network number. With a class-based IPv4 notation, this number also defines the IP network class (in this example class B) that would have been registered by the IANA.

Host component of the IPv4 address. The host component uniquely identifies an interface of a system in a network. Note that for every interface in a local network, the network component of the address is the same, but the host component must be different.

When planning a subnet for a class-based IPv4 network, you need a subnet mask or Netmask define. This is described in detail under Database.

The next example shows an address in CIDR format:

Figure 2–2 IPv4 address in CIDR format

Part of the network consisting of the IPv4 network number obtained from an ISP or an IR.

Host part that you assign to an interface in the system.

Network prefix that defines how many bits of the address make up the network number. The network prefix also provides the subnet mask for the IP address. Network prefixes are also assigned by the ISP or an IR.

In an Oracle Solaris-based network, standard IPv4 addresses, IPv4 addresses in CIDR format, DHCP addresses, IPv6 addresses, and private IPv4 addresses can be combined.

Create an IPv4 addressing scheme

This section describes the classes into which standard IPv4 addresses are organized. Although the IANA no longer issues class-based network numbers, these network numbers are still used in many networks. You may need to manage the address space for a location with class-based network numbers. For a full discussion of IPv4 network classes, see Network classes.

The following table shows the division of a standard IPv4 address into the network and host address spaces. For each class, "range" indicates the range of decimal numbers for the first byte of the network number. "Network Address" indicates the number of bytes of the IPv4 address assigned to the network portion of the address. Each byte is represented by. "Host Address" indicates the number of bytes of the IPv4 address assigned to the host portion of the address. For example, with a class A network address, the first byte is intended for the network and the last three bytes for the host. For a class C network, the assignment is reversed.

Table 2–1 Distribution of the IPv4 classes


Byte range

Network number

Host address











The numbers in the first byte of the IPv4 address define whether the network is a class A, B, or C network. The remaining three bytes have a range from 0-255. The two numbers 0 and 255 are reserved. You can assign the numbers 1–254 to each byte, depending on the network class assigned by the IANA to your network.

The following table shows which bytes of the IPv4 address are allocated for you. The table also shows the range of numbers within each byte that you can assign to your hosts.

Table 2–2 Range of Available IPv4 Classes

Network class

Byte 1 area

Byte 2 area

Byte 3 area

Byte 4 area








Pre-assigned by IANA





Pre-assigned by IANA

Pre-assigned by IANA


IPv4 subnet number

Local networks with numerous hosts are often divided into subnets. When you divide your IPv4 network number into subnets, you must assign a network identifier to each subnet. You can maximize the efficiency of the IPv4 address space by using a few bits of the host component of the IPv4 address as the network identifier. If you use a network identifier, the specified component of the address becomes the subnet number. You can create a subnet number using a netmask, a bit mask that selects the network and subnet parts of an IPv4 address. For more information, see Creating the Network Mask for IPv4 Addresses.

Create a CIDR IPv4 addressing scheme

The network classes that originally represented IPv4 are no longer used in the global Internet. Today the IANA distributes classless addresses in CIDR format to the worldwide registration authorities. All IPv4 addresses that you obtain from an ISP are in the CIDR format shown in Figure 2–2.

The network prefix of the CIDR address indicates how many IPv4 addresses are available for hosts on your network. These host addresses are assigned to the interfaces on a host. If a host has several physical interfaces, you must assign a separate host address to each physical interface used.

The network prefix of a CIDR address also defines the length of the subnet mask. Most Oracle Solaris 10 commands recognize the CIDR prefix assignment of the subnet mask of a network. However, the Oracle Solaris installer and file require that you set up the subnet mask using the separated decimal notation. In both of these cases, use the separated decimal notation of the CIDR network prefix, as shown in the following table.

Table 2–3 CIDR prefixes and their decimal equivalents

CIDR network prefix

Available IP addresses

Subnet equivalent with separate decimal notation



















For more information on CIDR addresses, see the following sources:

Use private IPv4 addresses

The IANA has reserved three blocks of IPv4 addresses that can be used in private networks. These addresses are defined in RFC 1918, Address Allocation for Private Internet. You can these private addresses, also known as 1918 addresses, for systems in local networks within a company intranet. However, these private addresses are not valid on the Internet. Do not use these addresses on systems that need to communicate with systems outside the local network.

The following table lists the private IPv4 address ranges and the corresponding network masks.

IPv4 address range

Netmask - - - 

Applying IP addresses for network interfaces

To connect to a network, a system must have at least one physical network interface feature. Each network interface must have its own unique IP address. During the Oracle Solaris installation, you provide the IP address of the first interface that the installation program finds. Generally this interface is named 0, e.g. B. or. This interface is called primary network interface considered.

If you add a second network interface to a host, that interface must also have its own unique IP address. This makes the host one Multihomed-Host. On the other hand, if you add a second network interface to a host and enable IP forwarding, the host becomes a router. For a description, see Configuring an IPv4 Router.

Each network interface has a device name, a device driver and an assigned device file in the directory. The network interface has a device name such as or; these are device names for two frequently used Ethernet interfaces.

For more information and tasks related to interfaces, see Managing the Interfaces in the Solaris 10 3/05 or Chapter 6, Managing Network Interfaces (Tasks).

Note -

This book assumes that your systems have Ethernet network interfaces. If you want to work with other network media, please refer to the information on the configuration of these media in the documents supplied with the network interfaces.

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