Static IP Address

In some cases, we need to assign static IP addresses manually to network resources such as File servers; Exchange servers; name servers; domain controllers AD; DHCP servers and other servers in a large networking environment. Not just for network resources, static IP addresses can also be applied to network devices such as switches; and routers.

To be able to communicate on a private TCP/IP network or on the public Internet, each host on the network must be identified by a 32-bit IP address. The IP addresses are either “obtain automatically” from the DHCP servers or manually assigned with static IP address. These IP addresses can be grouped into two categories: public IP addresses and private IP addresses.

Public IP Addresses

Public addresses are the globally unique addresses that are connected to the Internet. Private addresses are confined to specific ranges that can be used by any private network but that cannot be seen on the public Internet.

Internet Assigned Numbers Authority (IANA) divides up the non-reserved portion of the IP address space and delegates responsibility for address allocation to a number of regional registries throughout the world. These registries include Asia-Pacific Network Information Center (APNIC), American Registry for Internet Numbers (ARIN), and Réseaux IP Européens (RIPE NCC). The regional registries allocate blocks of addresses to a small number of large Internet service providers (ISPs) that then assign smaller blocks to customers and smaller ISPs.

Typically, your ISP assigns you one public IP address for each of your computers that is directly connected to the ISP. This IP address can be assigned dynamically to each computer when the computer connects, or it can be reserved statically for your dedicated line or dial-up account.

Assigning the Public IP addresses to the WAN interfaces mostly done manually with static IP address, such as to the serial interface of the routers that link to WAN services (such as frame relay; ISDN network; and leased line services).

Private IP Addressing

The IANA has reserved a certain number of IP addresses that are never used on the global Internet. These private IP addresses are used for hosts that require IP connectivity but that do not need to be seen on the public network. The following table lists the private IP Addresses with 3 class types.

For those hosts within the internal network of your organization, you should design the network configuration for them using the private IP addresses. If you want a computer to serve as an essential network server, such as a DNS server, WINS server, or domain controller AD, you should plan to assign the servers a static IP address. Although you can assign static IP address by using DHCP address reservations, many administrators prefer to keep essential servers free of DHCP dependence and therefore assign addresses to these servers manually.

Manually assign static IP address configurations are recommended only when DHCP is not available or feasible. Administering manually assigned IP addresses can be time-consuming and confusing, especially in medium to large networks.

In a simple home networking where the DHCP server is not available, the IP addresses can be obtain automatically from the APIPA (Automatic Private IP Address) scheme starts from 169.254.0.1 until 169.254.255.254. APIPA is in the private addressing scheme that is not routable to the Internet.

See also:

• Designing IP address for multi site networks
• LAN topologies
• WAN technologies and services
• Routing protocols guide
• Virtual LAN tutorial