Local Address

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Definition of Local Address in Network Encyclopedia.

What is Local Address?

Local Address is the address that a computer on a TCP/IP network uses to access another computer on the same subnet of the network.

Local address is translated by NAT
Local address is translated by NAT

For example, consider a TCP/IP network with the following subnet scheme:

  • Network ID = 202.55.0.0
  • Subnet Mask = 255.255.240.0

Using this scheme, there are 14 possible subnets for the network:

  • Subnet 1 has hosts 202.55.16.1 through 202.55.31.254.
  • Subnet 2 has hosts 202.55.32.1 through 202.55.47.254.
  • Subnet 3 has hosts 202.55.48.1 through 202.55.63.254.
  • …
  • Subnet 14 has hosts 202.55.224.1 through 202.55.239.254.

Now consider the following three hosts on the network:

  • Host A = 202.55.38.147
  • Host B = 202.55.44.12
  • Host C = 202.55.59.6

From the point of view of Host A, which is located on Subnet 2:

  • Host B is located on the local subnet (Subnet 2), so Host B’s address is local to Host A.
  • Host C is located on a remote subnet (Subnet 3), so Host C’s address is remote to Host A.

Private IP address space

Both, the IPv4 and the IPv6 specifications define private IP address ranges. These addresses are used for local area networks (LANs) in residential, office, and enterprise environments. Private IP address spaces were originally defined in an effort to delay IPv4 address exhaustion.

Private network addresses are not allocated to any specific organization and anyone may use these addresses without approval from a regional Internet registry. However, IP packets addressed from them cannot be routed through the public Internet.

RFC1918 nameIP address rangeAddressesClasse
24-bit block10.0.0.0 – 10.255.255.25516.777.216A
20-bit block172.16.0.0 – 172.31.255.2551.048.576B
16-bit block192.168.0.0 – 192.168.255.25565.536C

Although the standard for class A and class B networks specify 8- and 16-bit masks respectively, it is common to subdivide these and assign other masks internally, resulting in a number of smaller subnets (e.g. 10.0.0.0/24, with room for thousands of 254-host subnets).

Private network use the same addresses

Since the private IPv4 address space is relatively small, many private IPv4 networks unavoidably use the same address ranges and hence the same addresses. This can create a problem when merging such networks, as multiple devices are likely to have the same address. In this case, networks or hosts must be renumbered, often a time-consuming task or a network address translator must be placed between the networks to translate or masquerade the duplicate addresses.

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