Chapter - 2 IPv6 Design Flashcards
How many more bits does IPv6 use for addresses than IPv4?
- 32
- 64
- 96
- 128
96 more bits.
What is the length of the IPv6 header?
- 20 bytes
- 30 bytes
- 40 bytes
- 128 bytes
C.
The IPv6 header is 40 bytes in length.
What address type is the IPv6 address FE80::300:34BC:123F:1010?
- Aggregatable global
- Unique-local
- Link-local
- Multicast
C.
The defining first hexadecimal digits for link-local addresses are FE8.
What are three scope types of IPv6 addresses?
- Unicast, multicast, broadcast
- Unicast, anycast, broadcast
- Unicast, multicast, endcast
- Unicast, anycast, multicast
D.
IPv6 addresses can be unicast, anycast, or multicast.
What is a compact representation of the address 3f00:0000:0000:a7fb:0000:0000: b100:0023?
- 3f::a7fb::b100:0023
- 3f00::a7fb:0000:0000:b100:23
- 3f::a7fb::b1:23
- 3f00:0000:0000:a7fb::b1:23
B.
Answers A and C are incorrect because you cannot use the double colons (::) twice. Answers C and D are also incorrect because you cannot reduce b100 to b1.
What does DNS64 do?
- It translates IPv6 addresses to IPv4.
- It is a DNS mechanism that is integrated into NAT-PT.
- It is a DNS mechanism that synthesizes AAAA records from A records.
- It is a DNS mechanism that is integrated into NAT64.
C.
DNS64 is a DNS mechanism that synthesizes AAAA records from A records.
What IPv6 address scope type replaces the IPv4 broadcast address?
- Unicast
- Multicast
- Broadcast
- Anycast
B.
The IPv6 multicast address type handles broadcasts.
What is the IPv6 equivalent to 127.0.0.1?
- 0:0:0:0:0:0:0:0
- 0:0:0:0:0:0:0:1
- 127:0:0:0:0:0:0:1
- FF::1
B.
The IPv6 loopback address is ::1.
Which of the following is an “IPv4-compatible” IPv6 address?
- ::180.10.1.1
- f000:0:0:0:0:0:180.10.1.1
- 180.10.1.1::
- 2010::180.10.1.1
A.
IPv4-compatible IPv6 addresses have the format ::d.d.d.d.
Which protocol maps names to IPv6 addresses?
- Address Resolution Protocol (ARP)
- Neighbor Discovery (ND)
- Domain Name System (DNS)
- DNSv2
5.
C.
The DNS maps fully qualified domain names to IPv6 addresses using (AAAA) records.
Which of the following are IPv6 enhancements over IPv4?
- Larger address space, globally private IP address, multicast
- Larger address space, globally unique IP addresses, no broadcasts
- Larger address space, globally private IP address, multicast
- Larger address space, address auto-configuration, enhanced broadcasts
B.
IPv6 increases the address space, which allows globally unique IP addresses. Broadcasts are no longer used.
Which of the following supports routing on IPv6 networks?
- RIPv3, OSPFv3, EIGRP for IPv6
- RIPng, OSPFv3, EIGRPv6
- RIPng, OSPFv3, EIGRP for IPv6
- RIPv2, OSPFv2, EIGRP
C
What changed from IPv4 to IPv6?
- Protocol Type became the Next Header field.
- ND is used rather than ARP.
- AAAA records are used rather than A records.
- All of these answers are correct.
D
ND = Neighbor Discovery Protocol - It operates at the link layer of the Internet model, and is responsible for gathering various information required for internet communication, including the configuration of local connections and the domain name servers and gateways used to communicate with more distant systems.
Which is not an IPv6 migration strategy?
- Dual-Stack
- IP Migrate
- Tunneling
- Translation
B.
IP Migrate is not an IPv4-to-IPv6 migration strategy
The IPv6 header length is fixed which has what benefit?
Header format efficiency: The IPv6 header length is fixed, reducing header processing time and thus allowing vendors to improve packet switching efficiency.
T/F: IPv6 hosts can automatically configure themselves, with or without a Dynamic Host Configuration Protocol (DHCP) server.
True.
Address autoconfiguration: This capability provides for dynamic assignment of IPv6 addresses. IPv6 hosts can automatically configure themselves, with or without a Dynamic Host Configuration Protocol (DHCP) server. Stateful and stateless autoconfiguration are supported.
IPv6 supports QoS by labeling flows with classes of traffic.
True.
Flow labeling capability: Instead of using a Type of Service field, as IPv4 does, IPv6 enables the labeling of packets belonging to a particular traffic class for which the sender requests special handling, such as quality of service (QoS) and real-time service. This support aids specialized traffic, such as real-time voice or video.
T/F: IPv6 eliminates broadcasts.
True.
Eliminate the use of broadcasts: IPv6 reduces unnecessary bandwidth usage by eliminating the use of broadcasts and replacing them with multicasts.
A special “all-nodes” IPv6 multicast address handles the broadcast function.
T/F: The IPv6 header is simpler than the IPv4 header.
True.
The IPv6 header is simpler than the IPv4 header. Some IPv4 fields have been eliminated or changed to optional fields.
The Fragment Offset fields and flags in IPv4 have been eliminated from the header.
IPv6 adds a Flow Label field for QoS mechanisms to use.
What size is the IPv6 header?
The IPv6 header size is 40 bytes.
What does the Version field in the IPv6 header indicate? How long is it?
Version: This field, which is 4 bits long, indicates the format, based on the version number, of the IP header.
These bits are set to 0110 for IPv6 packets.
What is the Traffic Class field used for and how long is it?
Traffic Class: This field, which is 8 bits in length, describes the class or priority of the IPv6 packet and provides functionality similar to that of the IPv4 Type of Service field.
What is the Flow Label field in the IPv6 header used for? How long is it?
Flow Label: This field, which is 20 bits in length, indicates a specific sequence of packets between a source and destination that requires special handling, such as real-time data (voice and video).
How long is the Payload Length field in the IPv6 header? What does it indicate?
Payload Length: This field, which is 16 bits in length, indicates the payload’s size, in bytes. Its length includes any extension headers.
What 8 bit field indicates the type of extension header, if present, that follows this IPv6 header?
Next Header: This field, which is 8 bits in length, indicates the type of extension header, if present, that follows this IPv6 header.
If a Next Header field is present, it identifies the upper-layer protocol (TCP or UDP). This field is called the Protocol field in the IPv4 header. It uses values defined by the Internet Assigned Numbers Authority (IANA).
What is the TTL field now called?
Hop Limit: This field, which is 8 bits in length, is decremented by 1 by each router that forwards the packets. If this field is 0, the packet is discarded.
T/F: Optional network layer information is not included in the IPv6 header.
True.
Optional network layer information is not included in the IPv6 header; instead, it is included in separate extended headers.
Some extended headers are the routing header, fragment header, and hop-by-hop options header.
- The routing header is used for source routing.
- The fragment header is included in fragmented datagrams to provide information to allow the fragments to be reassembled.
- The hop-by-hop extension header is used to support jumbo-grams.
Two important extended headers are the Authentication Header (AH) and the Encapsulating Security Payload (ESP) header. These headers are covered later in the chapter.
What are the leading 8 bits of an IPv6 address used for?
The leading 8 bits of an IPv6 address are called the FP, Format Prefix.
It can define the IPv6 address type or other reservations. These leading bits are of variable lengths.
Table 2-3 shows the allocation of address prefixes.
What is the hex prefix 0000::/8?
Unspecified, loopback, IPv4-compatible
What is the prefix 2000::/3?
Global unicast address; IANA unicast address assignments are limited within this range
What is the prefix FE80:/10?
Link-local unicast addresses
What is the prefix FF00::/8?
Multicast addresses
What does the address 0:0:0:0:0:0:0:0 signify?
An unspecified address is all 0s: 0:0:0:0:0:0:0:0.
It signifies that an IPv6 address is not specified for the interface. Unspecified addresses are not forwarded by an IPv6 router.
What is this address?
0:0:0:0:0:0:0:1
The IPv6 loopback address is 0:0:0:0:0:0:0:1.
This address is similar to the IPv4 loopback address 127.0.0.1.
What are the three types of IPv6 unicast addresses?
There are three types of unicast addresses:
- Global unicast addresses
- Link-local addresses
- Unique local addresses
The IPv6 unicast (one-to-one) address is a logical identifier of a single-host interface. With a unicast address, a single source sends to a single destination. It is similar to IPv4 unicast addresses.
What type of IPv6 address connect to the public network?
IPv6 global unicast addresses.
These unicast addresses are globally unique and routable.
The Global Routing Prefix field is generally __ bits in length, and the Subnet ID field is __ bits. The Interface ID field is __ bits in length and uniquely identifies the interface on the link.
Figure 2-2 shows the format of the standard IPv6 global unicast address.
The Global Routing Prefix field is generally 48 bits in length, and the Subnet ID field is 16 bits. The Interface ID field is 64 bits in length and uniquely identifies the interface on the link.
What is the Interface ID field, or the IPv6 64-bit identifier, of a machine with this MAC address?
MAC address: 01:00:0C:A4:BC:D0
The Interface ID field is obtained from the 48-bit MAC address of the host. The MAC address is converted to the EUI-64 identifier format by inserting the FFFE hexadecimal value in between the 24-bit leftmost and rightmost values.
For example, with the MAC address 01:00:0C:A4:BC:D0, the leftmost 24 bits are 01:00:0C, and the rightmost bits are A4:BC:D0. By inserting FFFE, the IPv6 64-bit identifier becomes 01:00:0C:FF:FE:A4:BC:D0
IPv6 link-local addresses are significant to nodes on only a ______ ______.
IPv6 link-local addresses are significant to nodes on only a single link.
Routers do not forward packets with link-local source or destination addresses beyond the local link.
Link-local addresses are identified by leading ___ hexadecimal numbers.
Link-local addresses are identified by leading FE8 hexadecimal numbers.
T/F: Link-local addresses are configured automatically or manually.
True.
FC00::/7 is what type of IPv6 address?
RFC 4193 defines the unique local address. Unique local addresses (ULAs) are designed for use in local networks and are not routable on the Internet. They substitute the deprecated site-local addresses. Unique local IPv6 addresses have a globally unique prefix. This global unique prefix is well known to allow for easy filtering at site boundaries.
Global aggregatable unicast addresses begin with what fixed prefix?
Global aggregatable unicast addresses are a type of global unicast address that allows the aggregation of routing prefixes. This aggregation makes it possible to reduce the number of routes in the global routing table. These addresses are used in links to aggregate (summarize) routes upward to the core in large organizations or to ISPs.
Global aggregatable addresses are identified by a fixed prefix of 2000::/3.
As shown in Figure 2-5, the format of the global aggregatable IPv6 address is a Global Routing Prefix field starting with binary 001, followed by the Subnet ID field and then the 64-bit Interface ID field. The device MAC address is normally used as the interface ID.
T/F: There is no allocated prefix to identify anycast addresses.
True.
An IPv6 anycast (one-to-nearest) address identifies a set of devices. There is no allocated prefix to identify anycast addresses. An anycast address is allocated from a set of global unicast addresses. These destination devices should share common characteristics and are explicitly configured for anycast.
This IPv6 multicast address: FF01:0:0:0:0:0:0:1
indicates what exactly? (as in which nodes in what scope)
FF01:0:0:0:0:0:0:1 is the all-nodes address for interface-local scope.
The first two bytes have all this information…
FF = Multicast (FP or Format Prefix)
0 = flag field
1 = scope field = interface local scope
the last 112 bits are the Group ID (::1) - “all nodes group”
As shown in Figure 2-6, the fields of the IPv6 multicast address are the FP, a value of 0xFF, followed by a 4-bit flags field, a 4-bit scope field, and 112 bits for the Group ID field.
And this IPv6 multicast address is the ______ for the ________: FF02:0:0:0:0:0:0:2
And this IPv6 multicast address is the all-routers address for the local link: FF02:0:0:0:0:0:0:2
What is an FP in in IPv6 address?
The leading 8 bits in the address define the specific IPv6 address type.
The variable-length field containing these leading bits is called a Format Prefix (FP)
An IPv6 unicast address is divided into two parts. The first part contains the address prefix, and the second part contains the interface identifier.
What type of IPv6 address begins with FF::/8?
As shown in Figure 2-6, the fields of the IPv6 multicast address are the FP (Format Prefix), in this case a value of 0xFF, followed by a 4-bit flags field, a 4-bit scope field, and 112 bits for the Group ID field.
A quick way to recognize an IPv6 multicast address is that it begins with FF::/8.
T/F:
The Group ID field identifies the multicast group within the given scope.
True.
The group ID is independent of the scope. A group ID of 0:0:0:0:0:0:1 identifies all nodes, whereas a group ID of 0:0:0:0:0:0:2 identifies all routers.
Some well-known multicast addresses are listed in Table 2-5; they are associated with a variety of scope values.
T/F:
The SCOP (scope) field limits the scope of the multicast group.
True.
Match the following well-known multicast addresses with their definitiions.
- FF01::1
- FF02::1
- FF01::2
- FF02::2
- All routers (link-local)
- All nodes (link-local)
- All routers (interface-local)
- All nodes (interface-local)
FF01::1 All nodes (interface-local)
FF02::1 All nodes (link-local)
FF01::2 All routers (interface-local)
FF02::2 All routers (link-local)
Match the following well known multicast address to their definitions:
- FF02::5
- FF02::6
- FF02::9
- FF02::A
- RIPng
- EIGRP routers
- OSPFv3 all routers
- OSPFv3 designated routers
FF02::5 - OSPFv3 all routers
FF02::6 - OSPFv3 designated routers
FF02::9 - RIPng
FF02::A - EIGRP routers
Matchy-matchy time.
- Unicast
- Anycast
- Multicast
- An IP address that reaches a group of hosts identified by the address. It can be only a destination address.
- The IP address of an interface on a single host. It can be a source or destination address.
- An IP address that identifies a set of devices within an area. It can be only a destination address.
Unicast The IP address of an interface on a single host. It can be a source or destination address.
Anycast An IP address that identifies a set of devices within an area. It can be only a destination address.
Multicast An IP address that reaches a group of hosts identified by the address. It can be only a destination address.
IPv6 Address Prefixes Matchy-matchy time.
- Loopback address
- Unspecified address
- Global unicast address
- Unique local unicast
- Link-local unicast address
- Multicast address
- OSPFv3
- EIGRP routers
- DHCP
- FF02::C
- FF02::5
- FF02::A
- 0000::0001
- FF00::/8
- 2000::/3
- FC00::/7
- FE80:/10
- 0000::0000
Loopback address 0000::0001
Unspecified address 0000::0000
Global unicast address 2000::/3
Unique local unicast FC00::/7
Link-local unicast address FE80:/10
Multicast address FF00::/8
OSPFv3 FF02::5
EIGRP routers FF02::A
DHCP FF02::C
IPv6 replaces ARP with the IPv6 __________.
IPv6 replaces ARP with the IPv6 ND protocol, Neighbor Discovery Protocol.
IPv6 ND uses ICMPv6.
T/F:
Other IPv6 mechanisms use ICMPv6 to determine neighbor availability, path MTU, destination link-layer address, or port reachability.
True.
The IPv6 ND protocol performs the following functions. One is incorrect… which one?
Stateless address autoconfiguration: The host can determine its full IPv6 address without the use of DHCP.
Duplicate address detection: The host can determine whether the address it will use is already in use on the network.
Prefix discovery: The host can determine the link’s IPv6 prefix. Parameter discovery: The host can determine the link’s MTU and hop count.
Address resolution: The host can determine the MAC addresses of other nodes without the use of ARP.
Router discovery: The host can find local routers with the help of DHCP.
Next-hop determination: The host can determine a destination’s next hop.
Neighbor unreachability detection: The host can determine whether a neighbor is no longer reachable.
Redirect: The host can tell another host if a preferred next hop exists to reach a particular destination.
Router discovery: The host can find local routers without DHCP.
IPv6 ND uses ICMPv6 to implement some of its functions. One of these is incorrect. Which one?
Router Advertisement (RA): Sent by routers to advertise their presence and link-specific parameters
Router Solicitation (RS): Sent by hosts to request RA messages from local routers
Neighbor Solicitation (NS): Sent by hosts to request link layer addresses of other hosts (also used for duplicate address detection)
Neighbor Advertisement (NA): Sent by hosts to initiate the sending of NS messages
Redirect: Sent to a host to notify it of a better next hop to a destination
Neighbor Advertisement (NA): Sent by hosts in response to NS messages
T/F: The link address resolution process uses NS messages to obtain a neighbor’s link layer address.
True.
Nodes respond with an NA message that contains the link layer address.
T/F: Given an IPv6 address, the AAAA record returns a domain name to the requesting host.
False. this is the same as an A record in IPv4. (Name-to-IP record.)
IPv4 uses A records to provide FQDN-to-IPv4 address resolution. DNS adds a resource record (RR) to support name-to-IPv6 address resolution. RFC 3596 describes the addition of a new DNS resource record type to support the transition to IPv6 name resolution. The new record type is AAAA, commonly known as “quad-A.”
Given a domain name, the AAAA record returns an IPv6 address to the requesting host.
T/F: Current DNS implementations need to be able to support A (for IPv4) and AAAA resource records, with type AAAA having the highest priority and A the lowest.
False. The opposite is true, IPv4 A records take priority.
T/F: Separate DNS servers are needed for IPv6 networks.
False.
For hosts that support dual-stack (IPv4 and IPv6), the application decides which stack to use and accordingly requests an AAAA or A record. As shown in Figure 2-7, the client device requests the AAAA record of the destination IPv6 server. The DNS server returns the IPv6 address. Note that this is the same DNS server that supports IPv4 addresses; no separate DNS servers are needed for IPv6 networks.
T/F:
IPv6 does not allow packet fragmentation throughout the internetwork.
True.
Only sending hosts are allowed to fragment. Routers are not allowed to fragment packets.
RFC 2460 specifies that the MTU of every link in an IPv6 address must be 1280 bytes or greater.
T/F: During Path MTU Discovery, nodes along the path send the ICMPv6 packet-too-big message to the sending host if the packet is larger than the outgoing interface MTU.
True.
RFC 1981 recommends that nodes should implement IPv6 path MTU discovery to determine whether any paths are greater than 1280 bytes.
ICMPv6 packet-too-big error messages determine the path MTU. Nodes along the path send the ICMPv6 packet-too-big message to the sending host if the packet is larger than the outgoing interface MTU.
Assignment of IPv6 addresses to a host can occur statically or dynamically.
Static IPv6 address assignment involves manual configuration on the host’s configuration files.
Dynamic IPv6 address assignment can be done via ______ or ______ methods.
Assignment of IPv6 addresses to a host can occur statically or dynamically.
Static IPv6 address assignment involves manual configuration on the host’s configuration files.
Dynamic IPv6 address assignment can be done via stateless or stateful methods.
Stateless address assignment may result in a ______ or ______ address.
Stateless address assignment may result in a link-local or globally unique address.