Chapter 4

block size

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

variable-length subnet masking (VLSM)

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

DHCPv6

The version of DHCP used with IPv6. DHCPv6 uses port number 546 for client-to-server communications and port number 547 for server-to-client communications.

subnet mask

32-bit value used with an IPv4 address to indicate what portion of the IP address is in the network ID versus what portion is the host ID

classful mask

A classful mask is the default subnet mask applied to Class A, B, and C IPv4 networks. Specifically, Class A networks have a classful mask of 255.0.0.0. Class B networks have a classful mask of 255.255.0.0, and Class C networks have a classful mask of 255.255.255.0.

RFC 1918

A document that defines the range of private IP addresses.

Automatic Private IP Addressing (APIPA)

A feature that allows a device to automatically assign itself an IP address on the 169.254.0.0 network when a DHCP server or manual configuration is unavailable.

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 by networked devices to obtain IP address information.

Loopback

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

Router Advertisement (RA)

A message that a router sends to advertise its presence together with various link and internet parameters, either periodically or in response to a router solicitation message.

prefix notation

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

dotted decimal notation

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

Link-local

A non-routable IP address that is usable only on a local subnet

Classless Interdomain Routing (CIDR) notation

A process that involves shortening a classful subnet mask by removing right-justified 1s from a classful mask. As a result, it will allow contiguous classful networks to be aggregated.

Neighbor Discovery Protocol (NDP)

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

Private IP address

A range of Class A, B, and C addresses are designed for private use. Although these networks are routable within an organization, service providers do not route these private networks over the public internet.

Network Address Translation (NAT)

A technology that allows private ip addresses (as defined in RFC 1918) to be translated into internet-routable IP addresses (that is, public IP addresses).

Zeroconf

A technology that performs three basic functions: assigning link-local IP addresses, resolving computer names to IP addresses, and locating network services.

borrowed bits

Bits added to a classful subnet mask.

What can IPv6 networks use to assign IP addresses?

SLAAC

slash notation

See prefix notation.

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.

When you are configuring PAT as part of your address translation configuration, what is the source IP address used for translation with a large potential number of inside homes?

The IP address on the physical outside interface.

Dual Stack

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

Port Address Translation (PAT)

A variant of NAT in which multiple inside local IP addresses share a single inside global IP address. PAT can distinguish between different flows based on port numbers.

subinterface

A virtual interface on a single physical interface.

Which of the following are dynamic approaches to assigning routable IP addresses to networked devices?

BOOTP/DHCP

Anycast

Communication that has one to nearest (from the perspective of a router's routing table) flow.

Dynamic Host Configuration Protocol (DHCP)

Dynamically assigns IP address information (for example, IP address, subnet mask, DNS server's IP address, and default gateway's IP address) to network devices.

What technology allows for the automatic assignment of the host portion of IPv6 address?

EUI-64

Virtual IP addresses (VIP)

In load-balancing environments an address that is used to provide a single IP address for accessing a shared resource.

EUI-64

Literally, a standard for an extended unique identifier that is 64 bits long. Specifically for IPv6, a set of rules for forming a 64-bit identifier, used as the interface ID in IPv6 addresses, by starting with a 48-bit MAC address, inserting FFFE (hex) in the middle, and inverting the seventh bit.

What specifically does NAT allow to be translated into internet-routable IP addresses?

RFC 1918 private IP addresses

Unicast

a form of message delivery in which a message is delivered to a single destination

Multicast

a form of transmission in which a message is delivered to a group of hosts

Tunneling

a process that encrypts each data packet to be sent and places each encrypted packet inside another packet

What capability supported by the most router and switch manufacturers allows you to create many virtual interfaces out of a single physical interface?

sub interface