Network+ Chapter 5 IPv4 and IPv6 Addresses

*SECTION 5.3*

*Assigning IPv4 Addresses*

*SECTION 5.2*

*IPv4 Addressing*

*SECTION 5.4*

*SUBNETTING* Default subnet masks (that is, classful subnet masks) are not always the most efficient choice. Fortunately, you can add additional network bits to a subnet mask (thereby extending the subnet mask) to create subnets within a classful network.

Dynamic Configuration

- Instead of static IP address assignments, many corporate networks dynamically assign IP address parameters to their devices - early option for performing this automatic assignment of IP addresses was called Bootstrap Protocol (BOOTP for short) - most popular approach for dynamic IP address assignment is Dynamic Host Configuration Protocol (DHCP)

BOOTP

- developed as a method of assigning IP address, subnet mask, and default gateway information to diskless workstations

-- Locating network services

Examples of service discovery protocols include the standards-based Service Location Protocol (SLP), Microsoft's Simple Service Discovery Protocol (SSDP), and Apple's DNS-based Service Discovery (DNS-SD).

Unicast

Most network traffic is unicast in nature, meaning that traffic travels from a single source device to a single destination device.

-- Assigning link-local IP addresses

A link-local IP address is a nonroutable IP address usable only on a local subnet. APIPA is an example of a technology that assigns link-local IP addresses.

Broadcast

Broadcast traffic travels from a single source to all destinations on a network (that is, a broadcast domain). A broadcast address of 255.255.255.255 might seem that it would reach all hosts on all interconnected network. However, 255.255.255.255 targets all devices on a single network, specifically the network local to the device sending a packet destined for 255.255.255.255. Another type of broadcast address is a directed broadcast address, which targets all devices in a remote network. For example, the address 172.16.255.255 /16 is a directed broadcast targeting all devices in the 172.16.0.0 /16 network

IANA

The Internet Assigned Numbers Authority (IANA) is yet another entity responsible for IP address assignment. IANA is operated by ICANN and is responsible for IP address assignment outside of North America.

Multicast

- Multicast technology provides an efficient mechanism for a single host to send traffic to multiple, yet specific, destinations - What makes this possible is the use of a Class D address. A Class D address, such as 239.1.2.3, represents the address of a multicast group. The video server could, in this example, send a single copy of each video stream packet destined for 239.1.2.3. - Devices wanting to receive the video stream can join the multicast group. Based on the device request, switches and routers in the topology can then dynamically determine out of which ports the video stream should be forwarded.

ICANN

- Publicly routable IP addresses are globally managed by the Internet Corporation for Assigned Names and Numbers (ICANN) nonprofit corporation. - does not directly assign a block of IP addresses to your Internet service provider (ISP), but assigns a block of IP addresses to a regional Internet registry. - One example of a regional Internet registry is the American Registry for Internet Numbers (ARIN), which acts as an Internet registry for North America.

Zeroconf

- a technology supported on most modern operating systems and performs three basic functions: -- Assigning link-local IP addresses -- Resolving computer names to IP addresses -- Locating network services - If devices supporting these three Zeroconf features are interconnected on a local subnet, they can dynamically obtain link-local IP addresses, resolve one another's names to IP addresses, and discover services available on a network.

Classes of Addresses

- default subnet mask for a given IP address is solely determined by the value in the IP address's first octet - different classes of addresses - Classes A, B, and C are those ranges of addresses assigned to network devices. Class D addresses are used as destination IP addresses (that is, not assigned to devices sourcing traffic) for multicast networks, and Class E addresses are reserved for experimental use. - default subnet masks associated with address classes A, B, and C are called classful masks

Purpose of Subnetting

- example, 172.16.0.0/16 - a best practice is to take such a network address and subnet the network (thereby extending the number of network bits in the network's subnet mask) into additional subnetworks

Automatic Private IP Addressing

- networked device might be able to communicate on an IP network thanks to Automatic Private IP Addressing (APIPA) - feature allows a networked device to self-assign an IP address from the 169.254.0.0/16 network - address is usable only on the device's local subnet. (The IP address is not routable.) - designed as a solution for quickly setting up a localized network without the need to configure a DHCP server or the need to statically assign IP address information - remains a need for devices on this localized network to perform name resolution and discover network services. Fortunately, these needs are addressed by Zero Configuration (Zeroconf)

DHCP

- offers a more robust solution to IP address assignment than the solution offered by BOOTP - does not require a statically configured database of MAC address to IP address mappings - wide variety of options beyond basic IP address, subnet mask, and default gateway parameters -- server can educate a DHCP client about the IP address of a WINS server, or even an administrator-defined parameter

private IP addressing

- organization assigned one or more publicly routable IP addresses by its service provider often needs more IP addresses to accommodate all of its devices - solution is to use private IP addressing within an organization, in combination with Network Address Translation (NAT) -- NAT is a feature available on routers that allows private IP addresses used within an organization to be translated into a pool of one or more publicly routable IP addresses - Specific Class A, B, and C networks have been designed for private use - ISPs do not route these private networks over the public Internet

Types of Addresses

- three categories of IPv4 addresses: unicast, broadcast, and multicast

127 loopback Address

- used as a loopback IP address, meaning a locally significant IP address representing the device itself

Extending a Classful Mask

- way to take a classful network (that is, a network using a classful subnet mask) and divide that network into multiple subnets is by adding 1s to the network's classful subnet mask. However, the class of the IP address does not change, regardless of the new subnet mask. - class of a network is entirely determined by the value of the first octet. The class of a network has nothing to do with the number of bits in a subnet, making this an often-misunderstood concept

IP address parameters

IP address Subnet mask Default gateway Server addresses

WINS & UNC

In a company's internal network (that is, an intranet), a Microsoft Windows Internet Name Service (WINS) server might be used, as an example, to convert the names of network devices into their corresponding IP addresses. For example, you might attempt to navigate to a shared folder of \\server1\hrdocs. A WINS server could then be used to resolve the network device name of server1 to a corresponding IP address. The path of \\server1\hrdocs is in universal naming convention (UNC) form, where you are specifying a network device name (for example, server1) and a resource available on that device (for example, hrdocs). More and more companies today are transitioning to DNS even for internal network name resolution.

-- Resolving computer names to IP addresses

Multicast Domain Name Service (mDNS) is an example of a technology that can resolve computer names to their corresponding IP address on a local subnet, without the aid of a DNS server or a WINS server.

FQDN & DNS

When connecting to devices on the public Internet, a Domain Name System (DNS) server takes an FQDN and translates it into a corresponding IP address.