Appendix D -- Testing for Understanding Answers

Appendix D

Testing for Understanding Answers

This appendix contains the answers to the "Testing for Understanding" sections of Chapters 1 through 12.

Chapter 1: Introduction to IPv6

  1. What are the problems with IPv4 on today's Internet?

    Some of the problems are:

    • It has a rapidly depleting public address space.
    • There are large routing tables for Internet backbone routers.
    • Its configuration could be simpler.
    • Security at the IP level should be required so that applications can count on standardized Internet layer security services.
    • IPv4 has limited support for QoS delivery.
  2. How does IPv6 solve these problems?

    128-bit address length allows for a large public address space.

    Better address aggregation results in small routing tables for Internet backbone routers.

    IPv6 provides automatic configuration (even without DHCP).

    Security (IPSec) is an implementation requirement.

    Better support for QoS delivery using the Traffic Class and Flow Label fields.

  3. How does IPv6 provide better QoS support?

    IPv6 uses a combination of the Traffic Class field (to define a specific type of service) and the Flow Label field (which identifies that the packet requires special handling, even when the payload is encrypted).

  4. Describe at least three ways in which IPv6 is more efficient than IPv4.

    IPv6 addresses are hierarchical and summarizable, leading to smaller routing tables.

    The IPv6 address space removes the need for NATs, making end-to-end communication faster because no translation is needed.

    The IPv6 header is designed for minimal overhead and optimal processing at intermediate routers.

    IPv6 Neighbor Discovery (ND) replaces broadcast-based ARP with unicast and multicast ND messages. Common neighbor operations such as address resolution involve very few nodes.

    IPv6 hosts are self-configuring and do not require a DHCP server to discover addresses and other configuration information. Host startup times are reduced.

  5. Explain how NATs prevent peer-to-peer applications from working properly.

    Because each peer behind a NAT is represented by two addresses (a public address and a private address), peers cannot connect without manually configuring the NAT or relay address information about each other without making the peer-to-peer application NAT-aware.

  6. What are the key benefits of deploying IPv6 now?

    You will be able to take advantage of a much larger address space.

    You can get IPv6 address space in areas of the world that have very few available public IPv4 addresses.

    It would restore true end-to-end communication without intermediate translation. Peer-to-peer applications can now connect without compensating for one or more NATs between peers.

    IPv6 forwarding is more efficient and is address-scope aware.

Chapter 2: IPv6 Protocol for the Windows .NET Server 2003 F

  1. List and describe the features of the IPv6 protocol that allow for IPv4 and IPv6 coexistence.

    6to4 allows automatic tunneling and unicast IPv6 connectivity between IPv6/IPv4 hosts across the IPv4 Internet.

    ISATAP allows IPv6/IPv4 nodes within an IPv4 infrastructure of a site to use unicast IPv6 to communicate with each other and with nodes on an IPv6-enabled network, either within the site or the IPv6 Internet.

    6over4 allows IPv6/IPv4 nodes to communicate using IPv6 unicast or multicast over an IPv4 multicast-enabled infrastructure with each other and with nodes on an IPv6-enabled network, either within the site or the IPv6 Internet.

    PortProxy functions as a TCP proxy to facilitate the communication between nodes or applications that cannot connect using a common Internet layer protocol (IPv4 or IPv6).

  2. How do you configure the IPv6 protocol for the Windows .NET Server 2003 family after it has been installed?

    For most hosts, no configuration is required because stateless address autoconfiguration automatically configures addresses, routes, and other settings. To manually configure the IPv6 protocol for the Windows .NET Server 2003 family, use the netsh interface ipv6 commands.

  3. Under what circumstances will a Windows .NET Server IPv6 router advertise itself as a default router?

    A Windows .NET Server IPv6 router advertises itself as a default router if it has a default route that is configured to be published.

  4. List and describe the types of network communication in which both the client and server components are IPv6-enabled in the Windows .NET Server 2003 family.

    HTTP: Both Internet Explorer and IIS are IPv6-enabled.

    CIFS/SMB: Both the file- and printer-sharing client (the Workstation service) and server (the Server service) are IPv6-enabled.

  5. List the two ways to install the IPv6 protocol for the Windows .NET Server 2003 family.
    1. As a protocol for a LAN connection in the Network Connections folder.
    2. By using the netsh interface ipv6 install command.
  6. List how the common TCP/IP utilities have been enhanced to support IPv6 in the Windows .NET Server 2003 family.

    Ipconfig.exe now displays both IPv4 and IPv6 configurations.

    Route.exe now displays both IPv4 and IPv6 routing tables.

    Ping.exe now uses both ICMPv4 Echo and ICMPv6 Echo Request messages and supports additional options for IPv6.

    Tracert.exe now uses both ICMPv4 Echo and ICMPv6 Echo Request messages and supports additional options for IPv6.

    Pathping.exe now uses both ICMPv4 Echo and ICMPv6 Echo Request messages and supports additional options for IPv6.

    Netstat.exe now displays the IPv6 routing table and information about the IPv6, ICMPv6, TCP over IPv6, and UDP over IPv6 protocols.

Chapter 3: IPv6 Addressing

  1. Why is the IPv6 address length 128 bits?

    The IPv6 address length is 128 bits so that it can be divided into hierarchical routing domains that reflect the topology of the modern-day Internet. The use of 128 bits, 64 bits for the subnet ID and 64 bits for the interface ID, allows for multiple levels of hierarchy and flexibility in designing hierarchical addressing and routing between the backbone of the IPv6 Internet and the individual subnets within an organization's site.

  2. Define the Format Prefixes (FPs) for commonly used unicast addresses.

    Global: 001

    Link-local: 1111 1110 10

    Site-local: 1111 1110 11

  3. Express FEC0:0000:0000:0001:02AA:0000:0000:0007A more efficiently.

    FEC0::1:2AA:0:0:7A or FEC0:0:0:1:2AA::7A. By convention, when there are multiple equal-length blocks of zeros that can be compressed, the left-most block is compressed.

  4. How many bits are expressed by "::" in the addresses 3341::1:2AA: 9FF:FE56:24DC and FF02::2?

    In 3341::1:2AA:9FF:FE56:24DC, :: expresses 32 bits ((8 - 6) x 16).

    In FF02::2, :: expresses 96 bits ((8 - 2) x 16).

  5. Describe the difference between unicast, multicast, and anycast addresses in terms of a host sending packets to zero or more interfaces.

    A sending host uses a unicast address to send packets to a single interface (within the scope of the unicast address).

    A sending host uses a multicast address to send packets to zero or more interfaces belonging to the multicast group (within the scope of the multicast address).

    A sending host uses an anycast address to send packets to a single nearest interface belonging to the set of interfaces using the anycast address (within the scope of the anycast address).

  6. Why are no broadcast addresses defined for IPv6?

    All IPv4 broadcast addresses are replaced with IPv6 multicast addresses.

  7. Define the structure, including field sizes, of the aggregatable global unicast address.

    TLA ID - Top-Level Aggregation Identifier. The size of this field is 13 bits. The TLA ID identifies the highest level in the routing hierarchy. TLA IDs are administered by IANA and allocated to local Internet registries that, in turn, allocate individual TLA IDs to large, long haul ISPs.

    Res - Eight bits that are reserved for future use in expanding the size of either the TLA ID or the NLA ID.

    NLA ID - Next-Level Aggregation Identifier. The size of this field is 24 bits. The NLA ID allows an ISP to create multiple levels of addressing hierarchy within its network to both organize addressing and routing for downstream ISPs and identify organization sites.

    SLA ID - Site-Level Aggregation Identifier. The SLA ID is used by an individual organization to identify subnets within its site. The size of this field is 16 bits.

    Interface ID - Indicates the interface on a specific subnet. The size of this field is 64 bits.

  8. Define the scope for each of the different types of typically used unicast addresses.

    Global: The IPv6 Internet

    Site-local: A site, an organization network or portion of an organization's network that has a defined geographical location (such as an office, an office complex, or a campus)

    Link-local: A single link

  9. Explain how global and site-local addressing can share the same subnetting infrastructure within an organization.

    The global address and site-local address share the same structure beyond the first 48 bits of the address. In global addresses, the SLA ID field identifies the subnet within an organization. For site-local addresses, the Subnet ID field performs the same function. Because of this, you can create a subnetting infrastructure that is used for both site-local and global unicast addresses.

  10. Define the structure, including field sizes, of the multicast address.

    Flags - Indicates flags set on the multicast address. The size of this field is 4 bits.

    Scope - Indicates the scope of the IPv6 network for which the multicast traffic is intended to be delivered. The size of this field is 4 bits.

    Group ID - Identifies the multicast group and is unique within the scope. The size of this field is 112 bits. RFC 2373 recommends setting the 80 high-order bits to zero and using only the low-order 32 bits for the group ID.

  11. Why does RFC 2373 recommend using only the last 32 bits of the IPv6 multicast address for the multicast group ID?

    The last 32 bits of an IPv6 multicast address map to the last 32 bits of an Ethernet multicast MAC address. By using only the last 32 bits of the IPv6 multicast address as the group ID, there is a one-to-one correlation between a multicast group ID and an Ethernet multicast MAC address.

  12. Explain how the solicited-node multicast address acts as a pseudo-unicast address.

    Because the last 24 bits of the solicited-node multicast address either is based on the manufacturer ID portion of an IEEE 802 address or is randomly derived, the chances of two nodes on the same link having the same solicited-node multicast address is small. Therefore, because there is typically only one listener on a subnet for a given solicited-node multicast address, it is almost like using a unicast address.

  13. How do routers know the nearest location of an anycast group member?

    Routers within the routing domain of the anycast address have host routes that provide information on the location of the nearest anycast group member. Routers outside the routing domain of the anycast address have a summary route that provides information on the location of the routing domain of the anycast address.

  14. Perform a 4-bit subnetting on the site-local prefix FEC0:0:0:3D80::/57.

    The result is the following subnetted network prefixes:

    1 - FEC0:0:0:3D80::/61

    2 - FEC0:0:0:3D88::/61

    3 - FEC0:0:0:3D90::/61

    4 - FEC0:0:0:3D98::/61

    5 - FEC0:0:0:3DA0::/61

    6 - FEC0:0:0:3DA8::/61

    7 - FEC0:0:0:3DB0::/61

    8 - FEC0:0:0:3DB8::/61

    9 - FEC0:0:0:3DC0::/61

    10 - FEC0:0:0:3DC8::/61

    11 - FEC0:0:0:3DD0::/61

    12 - FEC0:0:0:3DD8::/61

    13 - FEC0:0:0:3DE0::/61

    14 - FEC0:0:0:3DE8::/61

    15 - FEC0:0:0:3DF0::/61

    16 - FEC0:0:0:3DF8::/61

  15. What is the IPv6 interface identifier for the universally administered, unicast IEEE 802 address of 0C-1C-09-A8-F9-CE? What is the corresponding link-local address? What is the corresponding solicited-node multicast address?

    ::E1C:9FF:FEA8:F9CE

    FE80::E1C:9FF:FEA8:F9CE

    FF02::1:FFA8:F9CE

  16. What is the IPv6 interface identifier for the locally administered, unicast EUI-64 address of 02-00-00-00-00-00-00-09? What is the corresponding link-local address?

    ::9

    FE80::9

  17. What is the site-local scope multicast address corresponding to the Ethernet multicast MAC address of 33-33-00-0A-4F-11?

    Assuming the RFC 2373 recommendation of using the last 32-bits of the multicast address as the multicast group ID, either FF05::A:4F11 (Transient flag set to 0) or FF15::A:4F11 (Transient flag set to 1).

  18. For each type of address, identify how the address begins in colon hexadecimal notation.

    Type of Address Begins with ...

    Link-local unicast address

    FE80

    Site-local unicast address

    FEC0

    Global address

    2 or 3

    Multicast address

    FF

    Link-local scope multicast address

    FF02 or FF12

    Site-local scope multicast address

    FF05 or FF15

    Solicited-node multicast address

    FF02::1:FF

    IPv4-compatible address

    ::

    IPv4-mapped address

    ::FFFF

    6to4 address

    2002:

Chapter 4: The IPv6 Header

  1. Why does the IPv6 header not include a checksum?

    In IPv6, the link layer performs bit-level error detection for the entire IPv6 packet.

  2. What is the IPv6 equivalent to the IHL field in the IPv4 header?

    There is no equivalent. The IPv6 header is always a fixed size of 40 bytes.

  3. How does the combination of the Traffic Class and Flow Label fields provide better support for QoS traffic?

    The Traffic Class field is equivalent to the IPv4 Type of Service field. The Flow Label field allows the flow—the series of packets between a source and destination with a non-zero flow label—to be identified by intermediate routers for non-default QoS handling without relying on upper-layer protocol stream identifiers such as TCP or UDP ports (which may be encrypted with ESP).

  4. Which extension headers are fragmentable and why? Which extension headers are not fragmentable and why?

    Fragmentable:

    Authentication header - Needed only by final destination

    ESP header and trailer - Needed only by final destination

    Destination Options header (for final destination) - Needed only by final destination

    Not fragmentable:

    Hop-by-Hop Options header - Needed by every intermediate router

    Destination Options header (for intermediate destinations) - Might be needed by intermediate destinations

    Routing header - Might be needed by intermediate destinations

    Fragment header - Not present prior to fragmentation

  5. Describe a situation that results in an IPv6 packet that contains a Fragment header in which the Fragment Offset field is set to 0 and the More Fragments flag is not set.

    IPv6 packets sent to IPv4 destinations that undergo IPv6-to-IPv4 header translation may receive a path MTU update of less than 1,280. In this case, the sending host sends IPv6 packets with a Fragment header and a smaller payload size of 1,272 bytes. In the Fragment header, the Fragment Offset field is set to 0 and the More Fragments flag is not set. The Fragment header is included so that the IPv6-to-IPv4 translator can use the Identification field in the Fragment header to perform IPv4 fragmentation to reach the IPv4 destination.

  6. Describe how the new upper-layer checksum calculation affects transport layer protocols such as TCP and UDP.

    TCP and UDP implementations must be updated to perform the checksum calculation that includes the new IPv6 pseudo-header when sending or receiving data over IPv6.

  7. If the minimum MTU for IPv6 packets is 1,280 bytes, then how are 1,280-byte packets sent on a link that supports only 512-byte frames?

    The link layer must provide a fragmentation and reassembly scheme that is transparent to IPv6.

Chapter 5: ICMPv6

  1. How do you distinguish ICMPv6 error messages from ICMPv6 informational messages?

    The value of the Type field for error messages is in the range 0 to 127. (The high-order bit is set to 0.) The value of the Type field for informational messages is in the range 128 to 255. (The high-order bit is set to 1.)

  2. Which fields of the Echo Request message are echoed in the Echo Reply message?

    Identifier, Sequence Number, Data

  3. For a maximum-sized IPv6 packet with a Fragment extension header sent on an Ethernet link, how many bytes of the original payload are returned in an ICMPv6 Destination Unreachable message?

    1,184 bytes (1,280 - 40 byte IPv6 header - 8 byte ICMPv6 header - 40 byte IPv6 header - 8 byte Fragment header)

  4. How can you tell whether a returned packet was discarded by a firewall that is enforcing network policy or a router that could not resolve the link-layer address of the destination?

    If the Code field in the ICMPv6 Destination Unreachable message is set to 1, the packet was discarded by a firewall that is enforcing network policy. If the Code field is set to 3, a router could not resolve the link-layer address of the destination.

  5. Why is the MTU field in the ICMPv6 Packet Too Big message 4 bytes long when the Next Hop MTU field in the ICMPv4 Destination Unreachable-Fragmentation Needed and DF Set message is only 2 bytes long?

    The maximum IPv4 packet size is 65,535 bytes, a number that can be expressed with 16 bits. To support IPv6 jumbograms, 32 bits are needed to express the MTU of the link.

  6. Why isn't the ICMPv6 Parameter Problem-Unrecognized Option message sent when the 2 high-order bits of an option's Option Type field are set to either 00 (binary) or 01 (binary)?

    If the 2 high-order bits in the Option Type field are set to 00, the option is ignored. If the 2 high-order bits in the Option Type field are set to 01, the packet is silently discarded.

  7. Based on the IPv6 design requirement to minimize processing at IPv6 routers, why is there no equivalent to the ICMPv4 Source Quench message in IPv6?

    A Source Quench message is sent to inform a sending host to lower its transmission rate when the router is congested. To minimize the processing of the router, the router should devote its processing and resources to clearing the congestion, and not creating and sending Source Quench packets.

Chapter 6: Neighbor Discovery

  1. List the IPv4 facilities that are replaced by the IPv6 ND protocol.

    ARP, Gratuitous ARP, ICMP Router Discovery, Redirect

  2. List the capabilities of the IPv6 ND protocol that are not present in IPv4.

    Neighbor unreachability detection; ability to advertise changes in link-layer addresses and the node's role on the network; ability to advertise configuration parameters, address prefixes, and routes.

  3. List the five different ND messages and the options that can be included with them.

    Router Solicitation: Source Link-Layer Address option

    Router Advertisement: Source Link-Layer Address, Prefix Information, MTU, Advertisement Interval, Home Agent Information, Route Information options

    Neighbor Solicitation: Source Link-Layer Address option

    Neighbor Advertisement: Target Link-Layer Address option

    Redirect: Redirected Header, Target Link-Layer Address options

  4. Describe the interpretation of the Length field in ND options.

    The Length field is the number of 8-byte blocks in the entire Neighbor Discovery option.

  5. What is the value of the Length field for a maximum-sized Redirected Header option (assuming no IPv6 extension headers are present)?

    [1280 - 40 (IPv6 header) - 40 (ICMPv6 Redirect message header)]/8 = 150

  6. Describe how you would use the MTU option to provide seamless connectivity between Ethernet nodes and ATM nodes on a transparently bridged link.

    Set the MTU option on the router to advertise a 1,500-byte link MTU so that the ATM nodes do not send 9,180-byte IPv6 packets.

  7. Why is the Source Link-Layer Address option not included in the Neighbor Solicitation message sent during duplicate address detection?

    It is not included because the reply must be multicast to all nodes on the link, rather than unicast to the sender of the Neighbor Solicitation message.

  8. Describe the configuration parameters and their corresponding fields sent in the Router Advertisement message (not including options). Describe the configuration parameters and their corresponding fields sent in the Prefix Information option.

    Router Advertisement message:

    • Default value of the Hop Limit field: Current Hop Limit
    • Whether to use a stateful address configuration protocol to obtain addresses or other configuration information: Managed Address Configuration flag, Other Stateful Configuration flag
    • Whether the advertising router is capable of acting as a home agent: Home Agent flag
    • The default router preference level of the advertising router: Default Router Preference
    • Whether the advertising router is a default router, and for how long: Router Lifetime
    • The value of the reachable time for neighbor unreachability detection: Reachable Time
    • The time interval between successive Neighbor Solicitation messages: Retransmission Timer

    Prefix Information option:

    • The prefix: Prefix Length, Prefix
    • Whether the advertised prefix is on-link: On-link flag
    • Whether to create a stateless address based on the prefix: Autonomous flag
    • Whether the Prefix field contains the address of the home agent: Router Address flag
    • Whether to update the site prefix table with a site prefix: Site Prefix flag, Site Prefix Length
    • The valid lifetime of the stateless address: Valid Lifetime
    • The preferred lifetime of the stateless address: Preferred Lifetime
  9. Under what circumstances is an unsolicited Neighbor Advertisement message sent?

    An unsolicited Neighbor Advertisement message is sent in response to a duplicate address detection Neighbor Solicitation and when either the link-layer address or the role of the node changes.

  10. What are the differences in address resolution and duplicate address detection node behavior for anycast addresses?

    In Neighbor Advertisement messages, the Override flag is always set to 0. Duplicate address detection is not performed for anycast addresses.

  11. Why is the response to a duplicate address detection sent as multicast? Who sends the response, the offending or defending node?

    The response is multicast because the sender of the Neighbor Solicitation message cannot receive unicast packets at the duplicated IPv6 address. The defending node always sends the response.

  12. Why is the value of the Hop Limit field set to 255 for all ND messages?

    To prevent ND-based attacks from being launched from off-link nodes. The Hop Limit field for all traffic of an off-link node is always less than 255.

  13. Describe the purpose of each of the host data structures described in RFC 2461.
    • Destination cache: maps a destination address to a next-hop address and stores the PMTU to the destination
    • Neighbor cache: maps a next-hop address to a link-layer address and stores the state of the entry for neighbor unreachability detection
    • Prefix list: stores all the on-link prefixes
    • Default router list: stores all the routers that advertised themselves as default routers
  14. What field in the Redirect message contains the next-hop address of the better router to use for packets addressed to a specific destination? Describe how the contents of that field are used to update the conceptual host data structures for subsequent data sent to the destination.

    The Target Address field. The Target Address field updates the Next-hop Address field of the destination cache entry corresponding to the Destination Address field on the host that receives the Redirect message.

  15. Under what circumstances does a router send a Router Advertisement?

    Pseudo-periodically and in response to a Router Solicitation message.

  16. For Host A and Host B on the same link, why is the exchange of a Neighbor Solicitation message (sent by Host A to Host B) and a Neighbor Advertisement message (sent by Host B to Host A) not considered by Host B as proof that Host A is reachable?

    Host B receives no confirmation that Host A received and processed the Neighbor Advertisement sent by Host B.

  17. What is the next-hop address of a destination set to for a host that does not have a prefix matching the destination address or a default router?

    It is set to the destination address of the IPv6 packet. The destination is considered to be on-link.

Chapter 7: Multicast Listener Discovery

  1. Why is the IPv6 Router Alert Option used in the Hop-by-Hop Options header for MLD messages?

    The IPv6 Router Alert option is used to ensure that routers process MLD messages that are sent to multicast addresses on which the router is not listening.

  2. Which addresses are used as the source address in MLD messages?

    The Source Address field is set to the link-local address of the interface on which the message is being sent. If a Multicast Listener Report message is for a solicited-node multicast address corresponding to a unicast address for which duplicate address detection has not completed successfully, the source address is set to the unspecified address (::).

  3. How do you distinguish a general query from a multicast-address-specific query in the Multicast Listener Query message?

    In the general query, the Destination Address field in the IPv6 header is set to the link-local scope all-nodes multicast address (FF02::1) and the Multicast Address field in the MLD message is set to the unspecified address (::). In the multicast-address-specific query, the Destination Address field in the IPv6 header and the Multicast Address field in the MLD message are set to the specific address being queried.

  4. For which multicast addresses are Multicast Listener Report messages never sent?

    The link-local scope all-nodes multicast address (FF02::1)

  5. In which MLD message is the value of the Maximum Response Delay field significant?

    Multicast Listener Query (both general and multicast-address-specific)

  6. Describe the use of the Multicast Address field for each MLD message.
    • Multicast Listener Query: Requests reporting for all multicast addresses (except FF02::1) or for a specified multicast address
    • Multicast Listener Report: Reports group membership for the specified multicast address
    • Multicast Listener Done: Reports that there might not be any more members on the subnet for the specified multicast address

Chapter 8: Address Autoconfiguration

  1. List and describe the states of an IPv6 autoconfigured address.
    • Tentative: The address is in the process of being verified as unique
    • Valid: The address can be used for sending and receiving unicast traffic
      • Preferred: The address is valid and it can be used for unlimited communication
      • Deprecated: The address is valid but its use is discouraged for new communication
    • Invalid: The address can no longer be used to send or receive unicast traffic
  2. What is the formula for calculating the amount of time an autoconfigured address remains in the deprecated state?

    Valid Lifetime - Preferred Lifetime

  3. How does a router obtain addresses other than link-local addresses?

    It obtains them through manual configuration.

  4. According to RFC 2462, what addresses are autoconfigured for LAN interfaces on hosts when duplicate address detection for the EUI-64-derived link-local address fails? What is the behavior for the IPv6 protocol for the Windows .NET Server 2003 family and Windows XP?

    None.

    If the EUI-64-derived link-local address is a duplicate, the IPv6 protocol for the Windows .NET Server 2003 family and Windows XP can continue with the receipt of a multicast Router Advertisement message containing site-local or global prefixes and automatically configure site-local or global addresses based on the EUI-64-derived interface ID or a temporary global address with a randomly-derived interface ID.

  5. A host computer is running Windows .NET Standard Server and is assigned the IPv4 address 172.30.90.65 on its single LAN interface. IPv6 on this computer starts up and receives a Router Advertisement message on its LAN interface that contains both a site-local prefix (FEC0:0:0:29D8::/64) and a global prefix (3FFE:FFFF:A3:29D8::/64). List and describe the autoconfigured addresses for all interfaces on this host.

    LAN interface: FE80::[EUI-64 interface ID], FEC0::29D8:[EUI-64 interface ID], 3FFE:FFFF:A3:29D8:[EUI-64 interface ID], 3FFE:FFFF:A3: 29D8:[random interface ID]

    Automatic Tunneling Pseudo-Interface: FE80::5EFE:172.30.90.65

    Loopback Interface: ::1, FE80::1

Chapter 9: IPv6 and Name Resolution

  1. Why is the RFC 1886-defined DNS record for IPv6 name resolution named the "AAAA" record?

    It is named the "AAAA" record because 128-bit IPv6 addresses are four times longer than 32-bit IPv4 addresses, which use a host (A) record.

  2. What is the benefit to using the Windows .NET Server 2003 family DNS Server service over the Windows 2000 DNS Server service when manually configuring AAAA records?

    With the Windows .NET Server 2003 family DNS Server service, you can type the IPv6 address as a single string and use double-colons to compress a block of zeros.

  3. A host computer is running Windows .NET Standard Server and is assigned the IPv4 address 172.30.90.65 on its single LAN interface. IPv6 on this computer starts up and receives a Router Advertisement message on its Automatic Tunneling Pseudo-Interface that contains both a site-local prefix (FEC0:0:0:C140::/64) and a global prefix (3FFE:FFFF:A3:C140::/64). List the IPv6 addresses for the AAAA records registered with DNS by this host.

    FEC0::C140:0:5EFE:172.30.90.65, 3FFE:FFFF:A3:C140::5EFE:172.30 .90.65

  4. Describe the importance of address selection rules for a node running both IPv4 and IPv6 that is using a DNS infrastructure containing both A and AAAA records.

    Address selection rules decide which type of address (IPv4 vs. IPv6) and the scope of the address (public vs. private for IPv4 and link-local vs. site-local vs. global vs. coexistence for IPv6), for both the source and the destination addresses for subsequent communication.

Chapter 10: IPv6 Routing

  1. How does IPv6 determine the single route in the routing table to use when forwarding a packet?

    Based on the list of matching routes, the route that has the largest prefix length is chosen. If there are multiple longest matching routes, the router uses the lowest metric to select the best route. If there are multiple longest matching routes with the lowest metric, IPv6 can choose which routing table entry to use.

  2. Describe the conditions that would cause a router to send the following ICMPv6 error messages:

    ICMPv6 Packet Too Big

    The IPv6 MTU of the forwarding interface is lower than the size of the IPv6 packet being forwarded.

    ICMPv6 Destination Unreachable-Address Unreachable

    The neighboring destination node does not respond to Neighbor Solicitation messages being sent to resolve its link-layer address. Or, the packet is a ping-pong packet (a packet being sent to a destination address that does not exist on a point-to-point link).

    ICMPv6 Time Exceeded-Hop Limit Exceeded in Transit

    The Hop Limit field for a packet is less than 1 after decrementing it.

    ICMPv6 Destination Unreachable-Port Unreachable

    There is no application on the router listening on the UDP destination port (for packets sent to an address assigned to a router interface).

    ICMPv6 Destination Unreachable-No Route to Destination

    There is no matching route in the IPv6 routing table.

    ICMPv6 Parameter Problem-Unrecognized IPv6 Option Encountered

    The router processed an unrecognized option within a Hop-by-Hop Options or Destination Options (for intermediate destinations) extension header and the two high-order bits of the Option Type field were set to either 10 or 11.

  3. A host running the IPv6 protocol for the Windows .NET Server 2003 family or Windows XP is configured with the IPv4 address of 10.98.116.47 and receives a Router Advertisement message from a router advertising itself as a default router with the link-local address of FE80:: 2AA:FF:FE45:A431:2C5D, and containing a Prefix Information option to autoconfigure an address with the prefix FEC0:0:0:952A::/64 and a Route Information option with the prefix FEC0:0:0:952C::/64. Fill in the expected entries for the host in the following abbreviated routing table.
     Network Destination      Gateway -----------------------  ------------- ::/0                     FE80::2AA:FF:FE45:A431:2C5D FEC0:0:0:952A::/64       On-link FEC0:0:0:952C::/64       FE80::2AA:FF:FE45:A431:2C5D 
  4. What happens when a node running the IPv6 protocol for the Windows .NET Server 2003 family or Windows XP sends a packet and there is no matching route in the routing table? How is this different from the behavior of an IPv4 node?

    The IPv6 node assumes that the destination is on-link (a neighbor) and attempts to send the packet. If a sending IPv4 node does not find a matching route in the IPv4 routing table, it indicates an internal forwarding error and does not attempt to send the packet.

  5. Describe the difference between distance vector, link state, and path vector routing protocol technologies in terms of convergence time, ability to scale, ease of deployment, and appropriate use (intranet vs. Internet).
    • Distance vector: high convergence time, does not scale to large or very large networks, very easy to deploy, appropriate for use within a small intranet
    • Link state: low convergence time, scales to large networks, more difficult to deploy, appropriate for use within an intranet consisting of a single autonomous system
    • Path vector: low convergence time, scales to very large networks, difficult to deploy, appropriate for use between autonomous systems on the Internet
  6. Why is IDRPv2 a better choice than BGP-4 for the routing protocol to use on the IPv6 Internet?

    IDRPv2 does not use a separate autonomous system identifier. IDRPv2 uses IPv6 prefixes to identify an AS or a routing domain confederation.

  7. A static router running the IPv6 protocol for the Windows .NET Server 2003 family or Windows XP is configured with the following commands.

    netsh int ipv6 set int 4 forw=enabled adv=enabled

    netsh int ipv6 set int 5 forw=enabled adv=enabled

    netsh int ipv6 add rou FEC0:0:0:1A4C::/64 4 pub=yes

    netsh int ipv6 add rou FEC0:0:0:90B5::/64 5 pub=yes

    With just these commands being run on the static router, will a host on the subnet FEC0:0:0:90B5::/64 have a default route? Why or why not?

    No. In order for a static router running the IPv6 protocol for the Windows .NET Server 2003 family or Windows XP to advertise itself as a default router, it must have a default route that is configured to be published. For example, the command:

    netsh int ipv6 add rou ::/0 6 FE80::2AA:FF:FE19:9B84 pub=yes

    would add a publishable default route.

Chapter 11: Coexistence and Migration

  1. Describe the difference between migration and coexistence.

    Migration is the equipping and configuration of all nodes to replace one protocol (IPv4) with another (IPv6). Coexistence is the allowance of both types of protocols to maintain connectivity; an advantage while migration is occurring.

  2. Why do the criteria for the IPv4-to-IPv6 transition require no dependencies between IPv4 and IPv6 hosts, addresses, and routing infrastructure?

    To allow for the maximum amount of flexibility for organizations and the Internet to migrate from IPv4 to IPv6 when needed, without compromising existing connectivity.

  3. How does an IPv4-only host communicate with an IPv6-only host?

    It communicates by using an Application or Transport layer gateway or proxy that translates or proxies IPv4 traffic to IPv6 traffic, and vice versa. The PortProxy component of the IPv6 protocol for the Windows .NET Server 2003 family is an example of a Transport layer proxy.

  4. What is the difference between an IPv4-compatible address and an IPv4-mapped address?

    An IPv4-compatible address is used to automatically tunnel IPv6 traffic across an IPv4 infrastructure. An IPv4-mapped address is used by an IPv6 implementation to internally represent IPv4-only hosts and IPv4 addresses.

  5. Is the IPv6 protocol for Windows XP and the Windows .NET Server 2003 family a dual IP layer? Why or why not?

    No. The IPv6 protocol for Windows XP and the Windows .NET Server 2003 family includes a separate implementation of TCP and UDP and is known as a dual stack implementation.

  6. How are the source and destination addresses in the IPv4 header determined for IPv6 over IPv4 tunnel traffic?

    For configured tunneling, the source and destination IPv4 addresses are determined from the manually configured tunnel endpoints.

    For automatic tunneling, the source address is determined from the IPv4 address assigned to the interface that is forwarding the packets. The destination IPv4 address is derived from the next-hop address for the packet.

  7. Describe the components of the 6to4 address and how the address is mapped to an IPv4 address when forwarded across an IPv4 infrastructure by a 6to4 router using the 2002::/16 route.

    6to4 addresses have the following form:

    2002:WWXX:YYZZ:[SLA ID]:[Interface ID]

    in which WWXX:YYZZ is the NLA ID portion of a global address and the colon hexadecimal representation of a public IPv4 address (w.x.y.z) assigned to a site. The SLA ID and Interface ID are the same as defined for global addresses.

    When a 6to4 router forwards an IPv6 packet with a 6to4 destination address using the 2002::/16 route, it encapsulates the IPv6 packet with an IPv4 header. In the IPv4 header, the source address is the IPv4 address of the sending interface and the destination address is the IPv4 address w.x.y.z.

  8. What is the public IP address of the 6to4 router that is being used as a site border router for the ISATAP host with the address 2002:9D3C:2B5A:5:0:5EFE:131.107.24.103?

    157.60.43.90

  9. Describe how 6to4 and ISATAP can be used together.

    6to4 is used to create a global address space based on an IPv4 public address (6to4 provides the first 64 bits of an IPv6 address). ISATAP is used to create interface identifiers based on assigned IPv4 addresses (ISATAP provides the last 64 bits of an IPv6 address). By combining 6to4 and ISATAP, you can use IPv6 to communicate across multiple IPv4 infrastructures.

  10. For a 6over4 host using an Ethernet adapter, describe how the joining of an IPv6 multicast group on all interfaces creates two multicast entries in the table of interesting destination MAC addresses on the Ethernet adapter.

    When the host joins an IPv6 multicast group on a LAN interface, the IPv6 multicast address is mapped to an Ethernet multicast MAC address beginning with 33-33. This multicast address is added to the table of interesting destination MAC addresses on the Ethernet adapter.

    Because the host is a 6over4 host, the IPv6 multicast address is mapped to an IPv4 multicast address. When the host joins an IPv4 multicast group on a LAN interface, the IPv4 multicast address is mapped to an Ethernet multicast MAC address beginning with 01-00-5E. This multicast address is added to the table of interesting destination MAC addresses on the Ethernet adapter.

  11. A common misconception is that ISPs must support native IPv6 routing in order to use IPv6. Describe why this is a misconception.

    By using 6to4, the ISP does not have to support native IPv6 routing. The ISP has to provide only IPv4 routing and the allocation of a single public IPv4 address to each customer.

Chapter 12: IPv6 Mobility

  1. How does a mobile node determine its home subnet prefix, home address, and the address of its home agent?

    Manual configuration - The home subnet prefix, home address, and the address of the home agent are manually configured, typically through a keyboard-based command, and are permanent until manually changed.

    Pseudo-automatic configuration - The user has the option (typically through a button in the user interface of the operating system) to indicate to the IPv6 protocol that the node is now connected to the home link. Based on this indication, the IPv6 protocol stores the home subnet link prefix and home address and listens for additional router advertisements containing the Home Agent (H) flag.

    Automatic configuration - The IPv6 node is always listening for router advertisements with the H flag set. Based on additional protocol or operating system parameters and the establishment of a security relationship with the home agent, the IPv6 node determines that it is on its home link.

  2. When does a home agent or correspondent node send a binding request?

    When the binding cache entry for the mobile node is about to expire.

  3. How does a home agent compile a list of home agents on the home link and then convey that information to the mobile node while it is away from home?

    The home agent compiles the list of home agents from received Router Advertisement messages with the H flag set. The list of home agents is conveyed to the mobile node through the ICMPv6 Home Agent Address Discovery process.

  4. How does the mobile node determine when it has attached to a new link?

    The link layer indicated a media change or because the node received a router advertisement that contains a new prefix.

  5. What kinds of packets are sent between the home agent and the mobile node?

    The mobile node sends the home agent the following types of packets:

    • Binding update
    • ICMPv6 Home Agent Address Discovery Request message

    The home agent sends the mobile node the following types of packets:

    • Binding maintenance (binding requests and binding acknowledgments)
    • ICMPv6 Home Agent Address Discovery Reply message
    • Tunneled data
  6. What kinds of packets are sent between the correspondent node and the mobile node?

    The mobile node sends the correspondent node the following types of packets:

    • Binding updates
    • Data (with the Home Address option in the Destination Options header)

    The correspondent node sends the mobile node the following types of packets:

    • Binding maintenance (binding requests or binding acknowledgments)
    • Data (with the Routing header)
  7. What kinds of packets are sent between the correspondent node and the home agent?

    Although there are no packets sent directly between the correspondent node and the home agent, the home agent intercepts packets sent by the correspondent node to the mobile node's home address and tunnels them to the mobile node's care-of address.

  8. Describe the addressing in the IPv6 header, and the sequence of IPv6 extension headers and their contents for a packet sent by a mobile node that is away from home to another mobile node that is away from home for which a binding cache entry is present.

    In the IPv6 header, the source address is set to the sending node's care-of address and the destination address is set to the destination node's care-of address.

    The Routing extension header contains the destination node's home address.

    The Home Address option in the Destination Options header contains the source node's home address.

  9. When does the mobile node send a binding update to the home agent? When does the mobile node send a binding update to the correspondent node?

    The mobile node sends a binding update to the home agent when it attaches to its first foreign link, changes to a new foreign link, returns home, or in response to a binding request.

    The mobile node sends a binding update to a correspondent node when it receives a packet from the correspondent node that was tunneled from the home agent, changes care-of addresses and the correspondent node is in its binding update list, or in response to a binding request.

  10. How does a mobile node determine when it has returned home?

    A mobile node determines it has returned home when it receives a router advertisement that contains its home prefix.

  11. How does the mobile node avoid duplicate address conflicts when it returns home?

    It does not perform duplicate address detection for its address. Instead, the mobile node informs the home agent that it has returned to the home link. After receiving a binding acknowledgment from the home agent, the mobile node then sends an unsolicited multicast Neighbor Advertisement message to the link-local scope all-nodes multicast address (FF02::1) with the Override (O) flag set to inform local hosts of the correct link-layer address for the mobile node's home address.



Understanding IPv6
Understanding Ipv6
ISBN: 0735612455
EAN: 2147483647
Year: 2005
Pages: 124
Authors: Joseph Davies

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