IP Addressing Structure
The dotted decimal structure of a binary IP address
- 8-bit binary number forms an octet
- Represented in dotted decimal form
- 32-bit binary address
- Having Network and Host portion (hierarchical addressing)
Convert 8-bit binary to decimal
E.g. Convert 0101100 00010000 00000100 00010100 to 172.16.4.20
E.g. Convert 172.16.4.20 to binary
Type of IP Addresses
Three types of addresses in the network
Network Prefix
Network prefix (or slash format) - the number of bits in the address that gives us the network portion.
E.g. 172.16.4.0 /24, the /24 is the prefix length - the first 24 bits are the network address.
E.g. Change in prefix length
172.16.4.0 /26, the /26 is the prefix length - the first 26 bits are the network address.
Different Prefixes for different host addresses and broadcast address in a network
Different prefixes
The network address could remain the same, but the host range and the broadcast address are different for different prefix lengths.
More example
Determine the network, broadcast and host addresses for a given address and prefix combination
Types of communication
Three types of communication:
- Unicast – one to one
- Broadcast – one to all
- Multicast – one to many
Broadcasting Traffic
Directed Broadcast
A directed broadcast is sent to all hosts on a specific network.
172.16.4.255
Limited Broadcast
The limited broadcast is used for communication that is limited to the hosts on the local network.
255.255.255.255
Reserved IPv4 Address Ranges
Public and Private Host Addresses
Public address
Addresses are designed to be used in the hosts that are publicly accessible from the Internet
Private address
Blocks of addresses that are used in networks that require limited or no Internet access
Network Address Translation (NAT)
Services to translate private addresses to public addresses - hosts on a privately addressed network can have access to resources across the Internet.
NAT services can be implemented on a device at the edge of the private network.
Special IPv4 Addresses
Network and Broadcast Addresses - the first and last addresses in each network
Default Route - 0.0.0.0 - 0.255.255.255 (0.0.0.0 /8)
Loopback - hosts use to direct traffic to themselves.
127.0.0.0 - 127.255.255.255 (127.0.0.0 /8)
Ping the loopback address to test the configuration of TCP/IP on the local host.
Link-Local Addresses - automatically assigned to the local host by the operating system where no IP configuration is available (let say no DHCP service in dynamic configuration)
169.254.0.0 - 169.254.255.255 (169.254.0.0 /16)
TEST-NET Addresses - for teaching and learning purposes and used in documentation and network examples.
192.0.2.0 - 192.0.2.255 (192.0.2.0 /24)
Classful IPv4 Address
- Classful Addressing - historic method for assigning addresses and the issues associated with the method
- Classless Addressing – current method
Role of the subnet mask
How the subnet mask is used to create and specify the network and host portions of an IP address?
The prefix and the subnet mask are different ways of representing the SAME THING - the network portion of an address.
Leading Consecutive 1s in subnet mask
Trailing Consecutive 0s in subnet mask
Extracting network address
Use the subnet mask and ANDing process to extract the network address from the IP address.
Subnetting
Subnetting allows for creating multiple logical networks from a single address block.
We can use a router to connect these networks together, each interface on a router must have a unique network ID. Every node on that link is on the same network.
Calculating Addresses
Use the subnet mask to divide a network into smaller networks and describe the implications of dividing networks for network planners
Formula for calculating the number of subnets:
2^n where n = the number of bits borrowed
Formula for calculating the number of usable hosts:
2^m - 2 where m = the number of bits left for hosts.
Example with 3 subnets: (2^2 = 4 > 3)
Given a subnet address and subnet mask, calculate the network address, host addresses and broadcast address
Given a pool of addresses and masks, assign a host parameter with address, mask and gateway
Given a diagram of a multi-layered network, address range, number of hosts in each network and the ranges for each network, create a network scheme that assigns addressing ranges to each network
Planning to Address Network
The allocation of these addresses inside the networks should be planned and documented for the purpose of:
Preventing duplication of addresses
Each host in an internetwork must have a unique address.
Providing and controlling access
Access to resources such as server can be controlled by the Layer 3 address.
Monitoring security and performance
We examine network traffic looking for addresses that are generating or receiving excessive packets.
Assigning Addresses
- Only those devices that will directly access the Internet - such as web servers - require a public address.
- A NAT service allows those devices with private addresses to share the remaining public addresses.
Assigning Addresses within a network
Some examples of different types of hosts are:
- End devices for users
- Servers and peripherals
- Hosts that are accessible from the Internet
- Intermediary devices
Assigning Addresses
Statically through an administrator
Static addresses - for printers, servers, and other networking devices
It is time-consuming to enter the information on each host.
Dynamically through DHCP
A preferred method of assigning IP addresses to hosts on large networks
Internet Assigned Numbers Authority (IANA) ( http://www.iana.net ) is the master holder of the IP addresses.
Regional Internet Registries (RIRs) - manage for particular purposes or for regional areas
ISPs are designated by a hierarchy based on their level of connectivity to the Internet backbone.
Each lower tier obtains connectivity to the backbone via a connection to a higher tier ISP.
The Development of IPv6
- The exhaustion of the IPv4 network addresses
- Improved packet handling
- Increased scalability and longevity
- QoS mechanisms
- Integrated security
IPv6 features
- 128-bit hierarchical addressing - to expand addressing capabilities
- Header format simplification - to improve packet handling
- Improved support for extensions and options - for increased scalability/longevity and improved packet handling
- Flow labeling capability - as QoS mechanisms
- Authentication and privacy capabilities - to integrate security
Testing the Network Layer
- Ping is a utility for testing IP connectivity between hosts.
- Ping uses a Layer 3 protocol called Internet Control Message Protocol (ICMP).
- Ping uses an ICMP Echo Request datagram.
- If the host at the specified address receives the Echo request, it responds with an ICMP Echo Reply datagram.
Pinging the Local Loopback (127.0.0.1) – Testing if TCP/IP configuration is properly installed on the host
Ping Gateway - Testing Connectivity to the Local LAN
Ping Remote Host - Testing Connectivity to Remote LAN
Use tracert/traceroute to observe the path between two devices as they communicate and trace the steps of tracert/traceroute's operation
ICMP (Internet Control Message Protocol)
Services to provide feedback about issues related to the process of IP packets
ICMP Packet – Header
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