IPv6 Addressing Formats and Rules Quiz

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Questions and Answers

What is the primary purpose of the Global Routing Prefix in an IPv6 Global Unicast Address?

To enable routing of packets across the internet

To enable communication with devices on the same local link

To identify the host portion of the address

To identify the network portion of the address assigned by the provider (correct)

What is the purpose of the Interface ID in an IPv6 Global Unicast Address?

To enable routing of packets across the internet

To identify the host portion of the address (correct)

To enable communication with devices on the same local link

To identify the subnet ID

What is the command to configure an IPv6 GUA on an interface?

ipv6 config address/prefix-length

ipv6 address-config prefix-length

ipv6 address/prefix-length (correct)

ipv6 address prefix-length

What is the purpose of a Link-local Address (LLA) in IPv6?

To enable communication with devices on the same local link Signup and view all the answers

What is the purpose of a Router Solicitation (RS) message in IPv6?

To discover IPv6 routers Signup and view all the answers

What is the purpose of a Router Advertisement (RA) message in IPv6?

To inform hosts on how to obtain an IPv6 GUA Signup and view all the answers

What information is provided by a Router Advertisement (RA)?

Network prefix and prefix length, DNS addresses and domain name, and default gateway address Signup and view all the answers

What is a characteristic of SLAAC in IPv6?

Devices use either EUI-64 or random generation method to create an interface ID Signup and view all the answers

What does an RA instruct a device to use in Method 2?

SLAAC to create its own IPv6 GUA and a stateless DHCPv6 server Signup and view all the answers

What is obtained from a stateful DHCPv6 server in Method 3?

IPv6 GUA, prefix length, and addresses of DNS servers Signup and view all the answers

What is the role of EUI-64 in IPv6?

Inserting a 16-bit value into the middle of a 48-bit Ethernet MAC address Signup and view all the answers

What is the prefix of IPv6 multicast addresses?

ff00::/8 Signup and view all the answers

Which mechanism is used to reassemble data in the correct order in Guaranteed and Ordered Delivery?

Sequence numbers Signup and view all the answers

What is the primary function of flow control in TCP transmission?

To adjust the rate of data flow between source and destination Signup and view all the answers

How does a host determine the value of its Maximum Segment Size (MSS)?

By subtracting the IP and TCP headers from the Ethernet maximum transmission unit (MTU) Signup and view all the answers

What happens to email messages on the server when downloaded using POP?

They are deleted from the server Signup and view all the answers

What is the primary function of the DNS protocol?

To resolve names to IP addresses Signup and view all the answers

What is a key difference between TCP and UDP with regards to congestion control?

TCP employs congestion handling mechanisms, while UDP does not Signup and view all the answers

What type of record contains an end device's IPv6 address?

AAAA record Signup and view all the answers

What is the primary advantage of UDP over TCP?

Low overhead data transport Signup and view all the answers

Why is UDP unable to reorder datagrams into their transmission order?

Because it does not track sequence numbers Signup and view all the answers

What is the main function of the database in a DNS server?

To manage name-to-IP mappings Signup and view all the answers

What is the primary difference between POP and IMAP?

POP deletes emails from the server, IMAP keeps them Signup and view all the answers

In an IPv6 address, what does each 'x' in the preferred format x:x:x:x:x:x:x:x represent?

A 16-bit hextet Signup and view all the answers

What is the purpose of a FQDN?

To provide a recognizable name for a numeric IP address Signup and view all the answers

What is the purpose of the double colon (::) in IPv6 address representation?

To replace any single, contiguous string of one or more 16-bit hextets consisting of all zeros Signup and view all the answers

What is the primary difference between a unicast and an anycast IPv6 address?

Unicast addresses uniquely identify an interface, while anycast addresses can be assigned to multiple devices Signup and view all the answers

What is the recommended IPv6 prefix length for LANs and other types of networks?

/64 Signup and view all the answers

According to IPv6 Address Representation Rule 1, what can be omitted from an IPv6 address?

Leading 0s Signup and view all the answers

What happens to a packet sent to an anycast address?

The packet is routed to the nearest device having that address Signup and view all the answers

Study Notes

IPv6 Unicast Addresses

IPv6 devices typically have two unicast addresses: Global Unicast Address (GUA) and Link-local Address (LLA)
Global Unicast Address (GUA) is similar to a public IPv4 address, globally unique, and internet-routable
Link-local Address (LLA) is required for every IPv6-enabled device, used to communicate with other devices on the same local link, and not routable

IPv6 Global Unicast Address (GUA)

Global Routing Prefix: the prefix or network portion of the address assigned by the provider
Subnet ID: the area between the Global Routing Prefix and the Interface ID
Interface ID: equivalent to the host portion of an IPv4 address
Command to configure an IPv6 GUA on an interface: ipv6 address/prefix-length

IPv6 Link-local Address (LLA)

Enables a device to communicate with other IPv6-enabled devices on the same link
Packets with a source or destination LLA cannot be routed
Every IPv6-enabled network interface must have an LLA

Dynamic Addressing for IPv6 GUAs

RS and RA Messages: used to configure IPv6 GUAs
- Router Solicitation (RS): messages sent by host devices to discover IPv6 routers
- Router Advertisement (RA): messages sent by routers to inform hosts on how to obtain an IPv6 GUA
RA provides useful network information, including:
- Network prefix and prefix length
- Default gateway address
- DNS addresses and domain name
Three methods to configure an IPv6 GUA:
- SLAAC (Stateless Address Autoconfiguration)
- SLAAC with stateless DHCPv6 server
- Stateful DHCPv6

SLAAC (Stateless Address Autoconfiguration)

Allows a device to configure a GUA without the services of DHCPv6
Device uses either the EUI-64 or random generation method to create an Interface ID
Prefix is provided by the RA

SLAAC with Stateless DHCPv6

RA suggests devices use SLAAC to create its own IPv6 GUA
RA suggests devices use a stateless DHCPv6 server to obtain other information
Device uses the router LLA as the default gateway address

Stateful DHCPv6

RA instructs a device to use stateful DHCPv6 only
Device can receive:
- Automatically configured GUA
- Prefix length
- The addresses of DNS servers from a stateful DHCPv6 server

EUI-64 Process

Extended Unique Identifier (EUI) or modified EUI-64 process
Inserts a 16-bit value of fffe (in hexadecimal) into the middle of the 48-bit Ethernet MAC address of the client

IPv6 Multicast Addresses

Prefix: ff00::/8
Used to send a single IPv6 packet to multiple destinations

TCP Reliability

Data Loss and Retransmission: retransmit segments for unacknowledged data
TCP Flow Control: adjusts the rate of data flow between source and destination for a given session
Maximum Segment Size (MSS): the maximum amount of data that the destination device can receive
Congestion Avoidance: uses timers and algorithms to avoid and control congestion

UDP

Does not establish a connection
Provides low overhead data transport due to small datagram header and no network management traffic
Does not track sequence numbers or reorder datagrams into their transmission order

Domain Name Service (DNS)

Converts numeric IP addresses into a simple, recognizable name
FQDNs (Fully-Qualified Domain Names): used to identify a domain name, e.g. http://www.cisco.com
DNS protocol: defines an automated service that matches resource names with the required numeric network address
DNS server stores different types of resource records, including:
- A: an end device IPv4 address
- NS: an authoritative name server
- AAAA: an end device IPv6 address
- MX: a mail exchange record

DNS Message Format

DNS uses a hierarchical system to create a database to provide name resolution
Database file is only responsible for managing name-to-IP mappings