IPv4 & IPv6

unicast

A type of communication flow that is a one-to-one flow, meaning that traffic travels from a single source device to a single destination device. Most traffic is this type. IPv6 starts with 2000 to 3999.

Dynamic Host Configuration Protocol (*DHCP*)

Assigns IP address information and does not require statistically configured database of MAC address to IP address mappings.

borrowed bits

Bits added to a classful subnet mask. How many you use determines how many subnets are created and the number of usable hosts per subnet.

SLP, SSDP, DNS-SD

Service discovery protocols.

classless interdomain routing (*CIDR*)

Shortens a classful subnet mask by removing right-justified 1s from a classful mask. As a result, it allows contiguous classful networks to be aggregated (sometimes called route aggregation).

DHCP Version 6

The IPv6 version of *DHCP*.

private IP addresses

Specific Class A, B, and C networks that have been designed for private use. Service providers do not route these private networks over the public internet, although these networks are routable within an organization (with the exception of the 169.254.0.0-169.254.255.255 address range).

subnet mask

A 32-bit value (in IPv4) that indicates what portion of the IP address is the network ID versus what portion is the host ID. Class A: 255.0.0.0 or /8 Class B: 255.255.0.0 or /16 Class C: 255.255.255.0 or /24

octet

A grouping of 8 bits. An IPv4 address consists of four octets (that is, a total of 32 bits).

Bootstrap Protocol (*BOOTP*)

A legacy broadcast-based protocol used to assign IP address information to diskless workstations from a database stored on a server. Now, DHCP is primarily used instead.

Extended Unique Identifier-64 (*EUI-64*)

A method in IPv6 to calculate a unique host address portion for a node. It uses the 48-bite MAC address on a device to aid in the generation of the unique 64-bit host ID.

dual stack

The ability of a network interface to run multiple protocols, such as IPv4 and IPv6.

multicast

A type of communication flow where traffic flows from a single source out only to destinations on the network that want to receive it. Devices wanting to receive the data 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 data stream should be forwarded. Class D addresses makes this possible. IPv4 starts with 224 to 239 IPv6 starts with FF.

broadcast

A type of communication flow where traffic flows from a single source to all destinations on a network. Example: A broadcast address of 255.255.255.255 targets all devices on a single network. Example: The address 172.16.255.255 /16 is a directed broadcast targeting all devices in the 172.16.0.0 /16 network

IP address

A unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network. Composed of a network address and a host address. 32-bits for IPv4 128-bits for IPv6

neighbor discovery

Any process whereby network elements can discover each other on the network. In the case of EIGRP, hello packets are used, for example.

neighbor discovery protocol (*NDP*)

Defines five ICMPv6 packet types for important jobs: 1. router solicitation - hosts inquire with router solicitation messages to locate routers on an attached link. 2. router advertisement - routers advertise their presence together with various link and Internet parameters, either periodically or in response to a router solicitation message. 3. neighbor solicitation - used by nodes to determine the link layer address of a neighbor, or to verify that a neighbor is still reachable via a cached link layer address. 4. neighbor advertisement - used by nodes to respond to a neighbor solicitation message. 5. redirect - routers may inform hosts of a better first-hop router for a destination.

Class A

First octet: 1-126 NETWORK.HOST.HOST.HOST 8 bits for network addressing.

tunneling

Transmitting traffic with additional encapsulation.

prefix notation

A method of indicating how many bits are in a subnet mask. For example, /24 is for a 24-bit subnet mask. Also known as slash notation.

dotted-decimal notation

A method of writing an IPv4 address or subnet mask, where groups of 8 bits are separated by periods.

link-local IP address

A nonroutable IP address usable only on a local subnet. IPv6 starts with FE80.

multicast domain name service (*mDNS*)

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.

zeroconf

A technology that performs three basic functions: 1. assigning link-local IP addresses 2. resolving computer names to IP addresses 3. locating network services If devices supporting these three 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.

anycast

A type of communication flow that is a one-to-nearest flow (from the perspective of a router's routing table).

Automatic Private IP addressing (*APIPA*)

Allows a networked device to self-assign an IP address from the 169.254.0.0/16 network. Note that this address is only usable on the device's local subnet (meaning that the IP address is not routable).

default gateway

The IP address of a router (or multilayer switch) to which a networked device sends traffic destined for a subnet other than the device's local subnet.

classful mask

The default subnet mask applied to Class A, B, and C IPv4 networks. Class A: 255.0.0.0 (1-126) Class B: 255.255.0.0 (128-191) Class C: 255.255.255.0 (192-223) Class D: (224 to 239) Example: 172.16.40.56 is a Class B IP address, based on the value of the first octet (172), which falls in the Class B range of 128-191.

block size

The number of IP addresses in a subnet, including the subnet's address and the subnet's directed broadcast address.

interesting octect

The octet containing the last 1 in the subnet mask.

variable-length subnet masking (*VLSM*)

The process of assigning various subnetwork IDs in the network to issue the appropriate number of IP addresses.

router advertisement

The process routers use to broadcast their presence together with various link and Internet parameters, either periodically or in response to a Router Solicitation message.

scope

The specified range of IP addresses to be handed out by a DHCP server.

loopback

This type of interface on a network device is a logical (virtual) interface that is often used for testing purposes.

Class B

First octet: 128-191 NETWORK.NETWORK.HOST.HOST 16 bits for network addressing

Class C

First octet: 192-223 NETWORK.NETWORK.NETWORK.HOST 24 bits for network addressing