- •6 Addressing the Network - iPv4
- •6.0 Chapter Introduction
- •6.0.1 Chapter Introduction Page 1:
- •6.1 IPv4 Addresses
- •6.1.1 The Anatomy of an iPv4 Address Page 1:
- •6.1.2 Knowing the Numbers - Binary to Decimal Conversion Page 1:
- •6.2 Addresses for Different Purposes
- •6.2.1 Types of Addresses in an iPv4 Network Page 1:
- •6.1.3 Practicing Binary to Decimal Conversions Page 1:
- •6.1.4 Knowing the Numbers - Decimal to Binary Conversions Page 1:
- •6.1.5 Practicing Decimal to Binary Conversion Page 1:
- •6.2.2 Calculating Network, Hosts and Broadcast Addresses Page 1:
- •6.2.3 Unicast, Broadcast, Multicast - Types of Communication Page 1:
- •6.2.4 Reserved iPv4 Address Ranges Page 1:
- •6.2.5 Public and Private Addresses Page 1:
- •6.2.6 Special iPv4 Addresses Page 1:
- •6.2.7 Legacy iPv4 Addressing Page 1:
- •6.3 Assigning Addresses
- •6.3.1 Planning to Address the Network Page 1:
- •6.3.2 Static or Dynamic Addressing for End User Devices Page 1:
- •6.3.3 Assigning Addresses to Other Devices Page 1:
- •6.3.4 Who Assigns the Different Addresses? Page 1:
- •6.3.5 IsPs Page 1:
- •Isp Services
- •Isp Tiers
- •6.3.6 Overview of iPv6 Page 1:
- •6.4 Is It On My Network?
- •6.4.1 The Subnet Mask - Defining the Network and Host Portions Page 1:
- •6.4.2 AnDing - What Is In Our Network? Page 1:
- •6.4.3 The anDing Process Page 1:
- •6.5 Calculating Addresses
- •6.5.1 Basic subnetting Page 1:
- •6.5.2 Subnetting - Dividing Networks into Right Sizes Page 1:
- •6.5.3 Subnetting - Subnetting a Subnet Page 1:
- •Vlsm Chart
- •6.5.8 Addressing in a Tiered Internetwork Page 1:
- •6.6 Testing the Network Layer
- •6.6.1 Ping 127.0.0.1 - Testing the Local Stack Page 1:
- •6.6.2 Ping Gateway - Testing Connectivity to the Local lan Page 1:
- •6.6.3 Ping Remote Host - Testing Connectivity to Remote lan Page 1:
- •6.6.4 Traceroute (tracert) - Testing the Path Page 1:
- •6.6.5 IcmPv4 - The Protocol Supporting Testing and Messaging Page 1:
- •6.7 Labs and Activities
- •6.7.3 Activity: iPv4 Address Subnetting Part 1 Page 1:
- •6.7.4 Activity: iPv4 Address Subnetting Part 2 Page 1:
- •6.7.5 Lab: Subnet and Router Configuration Page 1:
- •6.8 Chapter Summaries
- •6.8.1 Summary and Review Page 1:
- •6.9 Chapter Quiz
- •6.9.1 Chapter Quiz Page 1:
6.2.6 Special iPv4 Addresses Page 1:
There are certain addresses that cannot be assigned to hosts for various reasons. There are also special addresses that can be assigned to hosts but with restrictions on how those hosts can interact within the network.
Network and Broadcast Addresses
As explained earlier, within each network the first and last addresses cannot be assigned to hosts. These are the network address and the broadcast address, respectively.
Default Route
Also presented earlier, we represent the IPv4 default route as 0.0.0.0. The default route is used as a "catch all" route when a more specific route is not available. The use of this address also reserves all addresses in the 0.0.0.0 - 0.255.255.255 (0.0.0.0 /8) address block.
Loopback
One such reserved address is the IPv4 loopback address 127.0.0.1. The loopback is a special address that hosts use to direct traffic to themselves. The loopback address creates a shortcut method for TCP/IP applications and services that run on the same device to communicate with one another. By using the loopback address instead of the assigned IPv4 host address, two services on the same host can bypass the lower layers of the TCP/IP stack. You can also ping the loopback address to test the configuration of TCP/IP on the local host.
Although only the single 127.0.0.1 address is used, addresses 127.0.0.0 to 127.255.255.255 are reserved. Any address within this block will loop back within the local host. No address within this block should ever appear on any network.
Link-Local Addresses
IPv4 addresses in the address block 169.254.0.0 to 169.254.255.255 (169.254.0.0 /16) are designated as link-local addresses. These addresses can be automatically assigned to the local host by the operating system in environments where no IP configuration is available. These might be used in a small peer-to-peer network or for a host that could not automatically obtain an address from a Dynamic Host Configuration Protocol (DHCP) server.
Communication using IPv4 link-local addresses is only suitable for communication with other devices connected to the same network, as shown in the figure. A host must not send a packet with an IPv4 link-local destination address to any router for forwarding and should set the IPv4 TTL for these packets to 1.
Link-local addresses do not provide services outside of the local network. However, many client/server and peer-to-peer applications will work properly with IPv4 link-local addresses.
TEST-NET Addresses
The address block 192.0.2.0 to 192.0.2.255 (192.0.2.0 /24) is set aside for teaching and learning purposes. These addresses can be used in documentation and network examples. Unlike the experimental addresses, network devices will accept these addresses in their configurations. You may often find these addresses used with the domain names example.com or example.net in RFCs, vendor, and protocol documentation. Addresses within this block should not appear on the Internet.
Links:
Local-Link addresses http://www.ietf.org/rfc/rfc3927.txt?number=3927
Special-Use IPv4 Addresses http://www.ietf.org/rfc/rfc3330.txt?number=3330
Multicast allocation: http://www.iana.org/assignments/multicast-addresses