IP Address Functions and Versions
– An IP address serves two main functions: network interface identification and location addressing.
– It identifies the host’s network interface and provides the location of the host in the network.
– The IP address is essential for establishing a path to the host.
– The header of each IP packet contains the IP address of the sending and destination hosts.
– Two versions of the Internet Protocol are in common use: IPv4 and IPv6.
– IPv4, the original version, uses a 32-bit address, while IPv6 uses a 128-bit address.
– IPv6 was standardized in 1998 due to the depletion of IPv4 addresses.
– IPv6 deployment started in the mid-2000s.
– IPv4 addresses are still prevalent, but IPv6 is gradually being adopted.
IPv4 Addressing and Subnetting
– An IPv4 address is 32 bits in size, allowing for 4,294,967,296 addresses.
– Some addresses are reserved for special purposes like private networks and multicast addressing.
– IPv4 addresses are represented in dot-decimal notation, with four decimal numbers ranging from 0 to 255.
– Each part of the address represents an octet of 8 bits.
– IPv4 addresses can also be presented in hexadecimal, octal, or binary representations.
– In the early stages of IP development, the network number was the highest order octet.
– Classful network architecture was introduced in 1981 to allow for more network assignments.
– Classful addressing had three classes (A, B, and C) for unicast addressing.
– Classful design reduced the number of hosts in higher-order classes.
– Classful network design was replaced by Classless Inter-Domain Routing (CIDR) in 1993.
Private IP Addresses and Address Assignment
– Initially, IP addresses were intended to be globally unique.
– Private networks, not connected to the internet, do not require globally unique IP addresses.
– Private networks use IP addresses from three non-overlapping ranges.
– Network address translation (NAT) is used to connect private networks to the internet.
– Private networks conserve public address space.
– IP addresses assigned dynamically or persistently.
– Dynamic IP addresses assigned using DHCP.
– DHCP avoids administrative burden and allows address sharing.
– DHCP lease has an expiration period, address may be reassigned.
– Static addressing used for network infrastructure equipment.
– Sticky IP addresses seldom change.
– Used in IPv4 and IPv6 configurations.
– Maximizes chance of assigning the same address each time.
– Provides stability in home or small-office setups.
– Different from static configurations which are used indefinitely.
– Link-local addressing for IPv4 networks in block 169.254.0.0/16.
– Link-local addresses automatically assigned in IPv6 block fe80::/10.
– Valid only on the local network segment or point-to-point connection.
– Not routable and cannot be the source or destination of internet packets.
– Automatic Private IP Addressing (APIPA) used for IPv4 address autoconfiguration.
IP Address Classification and Geolocation
– IP addresses are classified into several classes of operational characteristics: unicast, multicast, anycast, and broadcast addressing.
– Unicast addressing is the most common concept and refers to a single sender or receiver.
– Broadcast addressing is an addressing technique in IPv4 that sends data to all possible destinations on a network.
– Multicast addressing is associated with a group of interested receivers and uses specific address ranges in both IPv4 and IPv6.
– Anycast addressing is a one-to-many routing topology where data is transmitted to the closest receiver in the network.
– Geolocation is used to deduce the geographic position of a communicating peer.
– It helps determine the location of a host based on its IP address.
– Geolocation can have various applications in services and targeting specific regions.
– It provides valuable information for network analysis and security purposes.
Public IP Addresses, Firewalling, and Address Translation
– A public IP address is globally routable and not reserved for private networks.
– It allows communication between hosts on the global Internet.
– Public IP addresses assigned to home networks are visible by logging into the router configuration.
– Most public IP addresses are dynamic and change relatively often.
– Dynamic IP addresses prevent abuse and enhance security for home networks.
– Network administrators use firewall software to restrict public Internet traffic within private networks.
– IP addresses are used to discriminate traffic and apply IP address blocking or tailored responses.
– Blacklists and whitelists are used to maintain databases of restricted and permissible traffic.
– Firewalling is crucial for security and privacy considerations in network management.
– Multiple client devices can share an IP address using techniques like NAT or proxy servers.
– NAT masks the real originating IP address from the server receiving a request.
– NAT maps different IP addresses on a private network to different port numbers on the public network.
– Residential networks commonly use NAT implemented in a residential gateway.
– Address translation enables multiple devices in a private network to share a single public IP address.
An Internet Protocol address (IP address) is a numerical label such as 192.0.2.1 that is connected to a computer network that uses the Internet Protocol for communication. An IP address serves two main functions: network interface identification, and location addressing.
Internet Protocol version 4 (IPv4) defines an IP address as a 32-bit number. However, because of the growth of the Internet and the depletion of available IPv4 addresses, a new version of IP (IPv6), using 128 bits for the IP address, was standardized in 1998. IPv6 deployment has been ongoing since the mid-2000s.
IP addresses are written and displayed in human-readable notations, such as 192.0.2.1 in IPv4, and 2001:db8:0:1234:0:567:8:1 in IPv6. The size of the routing prefix of the address is designated in CIDR notation by suffixing the address with the number of significant bits, e.g., 192.0.2.1/24, which is equivalent to the historically used subnet mask 255.255.255.0.
The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA), and by five regional Internet registries (RIRs) responsible in their designated territories for assignment to local Internet registries, such as Internet service providers (ISPs), and other end users. IPv4 addresses were distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each, but have been exhausted at the IANA level since 2011. Only one of the RIRs still has a supply for local assignments in Africa. Some IPv4 addresses are reserved for private networks and are not globally unique.
Network administrators assign an IP address to each device connected to a network. Such assignments may be on a static (fixed or permanent) or dynamic basis, depending on network practices and software features.
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