Chapter - 2 IPv6 Design Flashcards
1
Q
How many more bits does IPv6 use for addresses than IPv4?
- 32
- 64
- 96
- 128
A
96 more bits.
2
Q
What is the length of the IPv6 header?
- 20 bytes
- 30 bytes
- 40 bytes
- 128 bytes
A
C.
The IPv6 header is 40 bytes in length.
3
Q
What address type is the IPv6 address FE80::300:34BC:123F:1010?
- Aggregatable global
- Unique-local
- Link-local
- Multicast
A
C.
The defining first hexadecimal digits for link-local addresses are FE8.
4
Q
What are three scope types of IPv6 addresses?
- Unicast, multicast, broadcast
- Unicast, anycast, broadcast
- Unicast, multicast, endcast
- Unicast, anycast, multicast
A
D.
IPv6 addresses can be unicast, anycast, or multicast.
5
Q
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
A
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.
6
Q
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.
A
C.
DNS64 is a DNS mechanism that synthesizes AAAA records from A records.
7
Q
What IPv6 address scope type replaces the IPv4 broadcast address?
- Unicast
- Multicast
- Broadcast
- Anycast
A
B.
The IPv6 multicast address type handles broadcasts.
8
Q
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
A
B.
The IPv6 loopback address is ::1.
9
Q
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
A.
IPv4-compatible IPv6 addresses have the format ::d.d.d.d.
10
Q
Which protocol maps names to IPv6 addresses?
- Address Resolution Protocol (ARP)
- Neighbor Discovery (ND)
- Domain Name System (DNS)
- DNSv2
5.
A
C.
The DNS maps fully qualified domain names to IPv6 addresses using (AAAA) records.
11
Q
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
A
B.
IPv6 increases the address space, which allows globally unique IP addresses. Broadcasts are no longer used.
12
Q
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
A
C
13
Q
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.
A
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.
14
Q
Which is not an IPv6 migration strategy?
- Dual-Stack
- IP Migrate
- Tunneling
- Translation
A
B.
IP Migrate is not an IPv4-to-IPv6 migration strategy
15
Q
The IPv6 header length is fixed which has what benefit?
A
Header format efficiency: The IPv6 header length is fixed, reducing header processing time and thus allowing vendors to improve packet switching efficiency.
16
Q
T/F: IPv6 hosts can automatically configure themselves, with or without a Dynamic Host Configuration Protocol (DHCP) server.
A
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.
17
Q
IPv6 supports QoS by labeling flows with classes of traffic.
A
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.
18
Q
T/F: IPv6 eliminates broadcasts.
A
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.
19
Q
T/F: The IPv6 header is simpler than the IPv4 header.
A
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.
20
Q
What size is the IPv6 header?
A
The IPv6 header size is 40 bytes.
21
Q
What does the Version field in the IPv6 header indicate? How long is it?
A
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.
22
Q
What is the Traffic Class field used for and how long is it?
A
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.
23
Q
What is the Flow Label field in the IPv6 header used for? How long is it?
A
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).
24
Q
How long is the Payload Length field in the IPv6 header? What does it indicate?
A
Payload Length: This field, which is 16 bits in length, indicates the payload’s size, in bytes. Its length includes any extension headers.
25
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).
26
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.
27
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.
28
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.
29
What is the hex prefix 0000::/8?
Unspecified, loopback, IPv4-compatible
30
What is the prefix 2000::/3?
Global unicast address; IANA unicast address assignments are limited within this range
31
What is the prefix FE80:/10?
Link-local unicast addresses
32
What is the prefix FF00::/8?
Multicast addresses
33
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.
34
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.
35
What are the three types of IPv6 unicast addresses?
**There are three types of unicast addresses:**
1. Global unicast addresses
2. Link-local addresses
3. 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.
36
What type of IPv6 address connect to the public network?
**IPv6 global unicast addresses.**
These unicast addresses are globally unique and routable.
37
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.
38
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
39
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.
40
Link-local addresses are identified by leading ___ hexadecimal numbers.
Link-local addresses are identified by leading **FE8** hexadecimal numbers.
41
T/F: Link-local addresses are configured automatically or manually.
True.
42
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.
43
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.
44
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.
45
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.
46
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
47
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.
48
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.**
49
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.
50
T/F:
The SCOP (scope) field limits the scope of the multicast group.
True.
51
_Match the following well-known multicast addresses with their definitiions._
1. FF01::1
2. FF02::1
3. FF01::2
4. FF02::2
1. All routers (link-local)
2. All nodes (link-local)
3. All routers (interface-local)
4. 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)
52
_Match the following well known multicast address to their definitions:_
1. FF02::5
2. FF02::6
3. FF02::9
4. FF02::A
1. RIPng
2. EIGRP routers
3. OSPFv3 all routers
4. OSPFv3 designated routers
FF02::5 - OSPFv3 all routers
FF02::6 - OSPFv3 designated routers
FF02::9 - RIPng
FF02::A - EIGRP routers
53
_Matchy-matchy time._
1. Unicast
2. Anycast
3. Multicast
1. An IP address that reaches a group of hosts identified by the address. It can be only a destination address.
2. The IP address of an interface on a single host. It can be a source or destination address.
3. 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.
54
IPv6 Address Prefixes Matchy-matchy time.
1. Loopback address
2. Unspecified address
3. Global unicast address
4. Unique local unicast
5. Link-local unicast address
6. Multicast address
7. OSPFv3
8. EIGRP routers
9. DHCP
1. FF02::C
2. FF02::5
3. FF02::A
4. 0000::0001
5. FF00::/8
6. 2000::/3
7. FC00::/7
8. FE80:/10
9. 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
55
IPv6 replaces ARP with the IPv6 \_\_\_\_\_\_\_\_\_\_.
IPv6 replaces ARP with the IPv6 **ND protocol,** Neighbor Discovery Protocol.
IPv6 ND uses ICMPv6.
56
T/F:
Other IPv6 mechanisms use ICMPv6 to determine neighbor availability, path MTU, destination link-layer address, or port reachability.
True.
57
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.
58
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
59
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.
60
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.**
61
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.
62
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.**
63
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.
64
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.
65
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.
66
Stateless address assignment may result in a ______ or ______ address.
Stateless address assignment may result in a **link-local** or **globally unique** address.
67
T/F:
As with IPv4, devices such as routers, switches, servers, and firewalls should have IPv6 addresses configured manually.
True.
Some things never change.
68
What does SLAAC stand for?
**S**tate**L**ess **A**ddress **A**uto**C**onfiguration
The dynamic configuration of link-local IPv6 addresses is a stateless autoconfiguration method—that is, without DHCP. Hosts obtain their link-local addresses automatically as an interface is initialized.
69
Put the following SLAAC (Link-Local) steps in order:
* The host joins the all-nodes multicast group to receive neighbor advertisements from other nodes. The neighbor advertisements include the subnet or prefix associated with the link.
* The host performs a duplicate address-detection process.
* If a host is already using the tentative IP address, that host replies with a neighbor advertisement.
* The host sends a neighbor-solicitation message with the tentative IP address (interface identifier) as the target.
* If the host receives no neighbor advertisement, the target IP address becomes the link-local address of the originating host. It uses the link-local prefix FE80::/10 (binary: 1111 1110 10).
1. **DAD**. - First, the host performs a duplicate address-detection process.
2. **join FF01::1** - The host joins the all-nodes multicast group to receive neighbor advertisements from other nodes. The neighbor advertisements include the subnet or prefix associated with the link.
3. **send NS -** The host then sends a neighbor-solicitation message with the tentative IP address (interface identifier) as the target.
4. **recieve NA?** - If a host is already using the tentative IP address, that host replies with a neighbor advertisement.
5. If the host receives no neighbor advertisement, the target IP address becomes the link-local address of the originating host. It uses the link-local prefix FE80::/10 (binary: 1111 1110 10)
70
_SLAAC of Globally Unique IPv6 Address_
T/F: After a host has autoconfigured a link-local address, it listens for router advertisement (RA) messages. These router messages contain the prefix address to be used for the network. The IPv6 address is then formed from the prefix plus the interface ID (which derives from the MAC address).
True.
This is the mechanism.
71
See the attached diagram. What will the resulting Globally Unique IPv6 Address as configured by SLAAC be?
Step 1. Router Advertisement (RA) messages are sent by Router 1.
Step 2. The client learns the prefix from the RA message. In the case of Figure 2-9, the prefix is **2001:abcd:1234/64**.
Step 3. The client identifier is created by splitting the local MAC address and adding **FF:FE** in the middle. Hence, in our example, the MAC address BAFF:FE23:5A6B becomes BAFF:FE**FF:FE**23:5A6B.
Step 4. The seventh bit of the first byte is flipped (binary 1011 10**1**0 becomes binary 1011 10**0**0); thus, the identifier becomes B**8**FF:FEFF:FE23:5A6B.
Step 5. The merging of the prefix and identifier becomes 2001:abcd:1234:0000:B8FF:FEFF:FE23:5A6B.
Step 6. The address is shortened to **2001:abcd:1234::B8FF:FEFF:FE23:5A6B**
72
T/F: DHCP Lite uses SLAAC to conifigure the IP address automatically and then a DHCP request is sent to the router from the client to request information like DNS server, domain name, SIP server info etc.
True.
73
T/F:
DHCPv6 assignment is stateful, whereas IPv6 link-local and globally unique autoconfiguration are not.
True.
74
IPv6 has integrated mechanisms to provide security for communications.
What are they?
It natively supports IP Security (IPsec).
Extension headers carry the IPsec AH and ESP headers. The AH provides authentication and integrity. The ESP header provides confidentiality by encrypting the payload. For IPv6, the AH defaults to Message Digest Algorithm 5 (MD5), and the ESP encryption defaults to Data Encryption Standard–Cipher Block Chaining (DES-CBC).
75
What is the next header number of ICMPv6?
ICMPv6 Performs diagnostics and reachability information. Has a Next Header number of 58.
76
What IPv6 service discovers all nodes in the same link and checks for duplicate addresses?
IPv6 **Neighbor Discovery:** Discovers all nodes in the same link and checks for duplicate addresses.
77
T/F:
Many RIP mechanisms remain the same with RIPng. It still has a 15-hop limit, uses counting to infinity, and split horizon with poison reverse.
True.
78
Instead of using User Datagram Protocol (UDP) port 520, as RIPv2 does, RIPng uses UDP port \_\_\_\_.
Instead of using User Datagram Protocol (UDP) port 520, as RIPv2 does, RIPng uses UDP port **521**.
79
RIPng uses multicast group _________ for RIP updates to all RIP routers.
RIPng uses multicast group **FF02::9** for RIP updates to all RIP routers.
80
This mechanism from IPv6 performs diagnostics and reachability information. It has a Next Header number of 58.
ICMPv6
81
This IPv6 mechanism discovers all nodes in the same link and checks for duplicate addresses.
ND - Neighbor discovery.
82
RIPng uses multicast group ________ for RIP updates to all RIP routers.
RIPng uses multicast group **FF02::9** for RIP updates to all RIP routers.
83
EIGRP uses multicast group ______ for EIGRP updates.
EIGRP uses multicast group **FF02::A** for EIGRP updates.
84
T/F: Network statements are used when configuring EIGRP for IPv6.
EIGRP for IPv6 is configured and managed separately from EIGRP for IPv4; **no network statements are used**. EIGRP for IPv6 retains all the characteristics (network discovery, DUAL, modules) and functions of EIGRP for IPv4.
85
OSPFv3 uses multicast group ______ for all OSPF routers and ______ for all DRs.
OSPFv3 uses multicast group **FF02::5** for all OSPF routers and **FF02::6** for all DRs.
86
When designing LAN subnets with IPv6, it is recommended that you use a /\_\_ subnet. This is similar to the /24 subnet in IPv4.
When designing LAN subnets with IPv6, it is recommended that you use a **/64** subnet. This is similar to the /24 subnet in IPv4.
IPv4. It provides more than enough addresses for devices contained in the subnet, allows for future growth, and prevents renumbering in the future. It also allows for easier aggregation of subnets.
87
What are the 5 Regional Internet Registries?
1. AfriNIC: Africa
2. APNIC: Asia Pacific
3. ARIN: Canada, the United States, and part of the Caribbean islands
4. LACNIC: Latin America and part of the Caribbean islands
5. RIPE NCC: Europe, the Middle East, and Central Asia
88
ULAs use the prefix \_\_\_\_\_\_\_
IPv6 private addressing should be very limited compared to its use in IPv4. IPv6 private IP addresses are referred to as unique local addresses (ULAs) and use the prefix **FC00::/7**. In both small and large companies, you should not expect to use ULAs in IPv6 networks. Furthermore, the Internet Engineering Task Force (IETF) does not recommend the use of NAT for IPv6. In the remote event that ULAs are needed, you will also use NAT66 for the IPv6-to-IPv6 private-to-public translation.
89
What are the migration strategies for IPv4 to IPv6?
**Dual-stack:** IPv4 and IPv6 coexist in hosts and networks.
**Tunneling:** IPv6 packets are encapsulated into IPv4 packets.
**Translation:** IPv6 packets are translated to IPv4 packets.
90
IPv6 deployment models are also divided into three major categories.
What are they? Which is recommended?
1. **Dual-stack model:** IPv4 and IPv6 coexist on hosts and the network.
2. **Hybrid model:** Combination of Intra-Site Automatic Tunneling Addressing Protocol (ISATAP) or manually configured tunnels and dual-stack mechanisms.
3. **Service block model:** Combination of ISATAP and manually configured tunnels and dual-stack mechanisms.
Each model provides several advantages and disadvantages, and you should familiarize yourself with them. Of all these models, the dual-stack model is recommended because it requires no tunneling and is easiest to manage.
91
T/F: When using dual-stack, a host also uses DNS to determine which stack to use to reach a destination.
True.
When using dual-stack, a host also uses DNS to determine which stack to use to reach a destination. If DNS returns an IPv6 (AAAA record) address to the host, the host uses the IPv6 stack. If DNS returns an IPv4 (A record) address to the host, the host uses the IPv4 stack. As mentioned before, current operating systems, such as Windows 10, macOS, and iOS, are configured to prefer IPv6 by default.
92
T/F:
One drawback of the IPv6 over IPv4 tunneling migration strategy is that both endpoints must support dual stack.
True.
In the IPv6 over IPv4 tunneling migration strategy, isolated IPv6-only networks are connected using IPv4 tunnels. With overlay tunnels, IPv6 packets are encapsulated within IPv4 packets so that they are sent over the IPv4 WAN. Overlay tunnels can be configured between border devices or between a border device and a host; however, **both tunnel endpoints must support the IPv4 and IPv6 protocol stacks.** The advantage of this method is that you do not need separate circuits to connect the IPv6 isolated networks.
93
T/F: A disadvantage of the IPv6 over IPv4 tunneling migration strategy is the increase in protocol overhead due to the encapsulation..
True.
A disadvantage of this method is the increased protocol overhead of the encapsulated IPv6 headers. Furthermore, overlay tunnels reduce the maximum transmission unit (MTU) by **20 octets.**
94
T/F: GRE tunnels work well to connect IPv6 sites during migration because the GRE has a protocol field that identifies the passenger protocol.
True.
IPv6 packets can also be carried over IPv4 generic routing encapsulation (GRE) tunnels for stable connectivity between two IPv6 domains. A GRE tunnel is not tied to a specific passenger or transport protocol and can support other Layer 3 protocols (such as IS-IS) over the same tunnel. Because GRE has a protocol field, it can identify the passenger protocol (such as IPv6 or IS-IS); therefore, it is advantageous to tunnel IS-IS and IPv6 inside GRE.
95
What is an IPv6 RD tunnel?
IPv6 Rapid Deployment (6RD) tunnels are an extension of 6to4 and allow a service provider to provide unicast IPv6 service to customers over its IPv4 network by using encapsulation of IPv6 in IPv4. It is defined in RFC 5969.
With 6RD, service providers do not have to use a 2002::/16 prefix; instead, they use a prefix from their own SP address block. The IPv6 operational domain is within the SP’s networks. Furthermore, with 6RD, the 32 bits of the IPv4 destination do not need to be carried within the IPv6 payload. The IPv4 destination is obtained from a combination of bits in the payload header and information on the router.
96
What is a 6to4 tunnel?
A tunnel from one IPv6 network over IPv4 infrastructure to another IPv6 network.
RFC 3056 specifies the 6to4 method for transition by assigning an interim unique IPv6 prefix. **2002::/16 is the assigned range for 6to4.** Each 6to4 site uses a /48 prefix that is concatenated with 2002.
An automatic 6to4 tunnel may be configured on a border router of an isolated IPv6 network to create a tunnel over an IPv4 infrastructure to a border router in another IPv6 network.
The border router extracts the IPv4 address that is embedded in the IPv6 destination address and encapsulates the IPv6 packet in an IPv4 packet with the extracted destination IPv4 address. The destination router extracts the IPv6 packet and forwards it to the IPv6 destination.
97
What is a ISATAP tunnel?
Another method to tunnel IPv6 over IPv4 is to use **Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)**.
With ISATAP, a tunnel is automatically created between dual-stack hosts or routers to transmit IPv6 packets over an IPv4 network within a site. ISATAP does not require IPv4 to be multicast enabled. ISATAP uses a well-defined IPv6 address format composed of any unicast prefix of 64 bits, which can be a link-local or global IPv6 unicast prefix. It then uses the 32 bits 0000:5EFE that define the ISATAP address ending with the 32-bit IPv4 address of the ISATAP link.
98
Deployment of IPv6 can be done in one of three models. What are these models?
**Dual-stack model:** IPv4 and IPv6 coexist on hosts and on the network.
**Hybrid model:** This model uses a combination of ISATAP or manually configured tunnels and dual-stack mechanisms.
**Service block model:** This model uses a combination of ISATAP and manually configured tunnels and dual-stack mechanisms.
99
What is the Dual-Stack Model?
In the dual-stack model, **devices and the network routers and switches all run both IPv4 and IPv6 protocol stacks.**
The applications on the devices decide which stack to use to communicate with destination hosts. Alternatively, DNS is used to decide which stack to use. A DNS AAAA RR return uses IPv6, and a DNS A RR return uses IPv4. Because most mature operating systems now support IPv6, this is the preferred technique for transition to IPv6.
100
What is a hybrid deployment model of IPv6?
The hybrid model uses a combination of transition mechanisms, depending on multiple network criteria, such as number of hosts, IPv6-capable hardware, and location of IPv6 services. The hybrid model can use these transition mechanisms:
* Dual-stack mechanism
* ISATAP
* Manually configured tunnels
The hybrid model can be used to tunnel a dual-stack host on an IPv4 access layer to an IPv6 core.
101
What is the Service Block Model of IPv6 deployment models?
**Service Block Model:** In the service block model, a centralized layer that services dual-stack devices is created with tunnels manually configured between the distribution layer and the service block. Dual-stack hosts also connect via ISATAP tunnels. In Figure 2-17, the dual-stack client on the left connects to the service block to establish connectivity with the dual-stack server on the right.
102
Dual-stack is also referred to as ______ mode.
Dual-stack is also referred to as **native** mode.
Devices running dual-stack can communicate with both IPv4 and IPv6 devices. The IPv4 protocol stack is used between IPv4 hosts, and the IPv6 protocol stack is used between IPv6 hosts. An application decides which stack to use to communicate with destination hosts. As shown in Figure 2-11, when a frame is received, the Ethernet type code identifies whether the packet needs to be forwarded to IPv4 (0x0800) or IPv6 (ox86DD).
103
What is a 6to4 tunnel? What is the assigned range of 6to4 tunnels?
This is one of the three automatic tunnel mechanisms.
**2002::/16 is the assigned range for 6to4.**
Each 6to4 site uses a /48 prefix that is concatenated with 2002.
An automatic 6to4 tunnel may be configured on a border router of an isolated IPv6 network to create a tunnel over an IPv4 infrastructure to a border router in another IPv6 network.
The border router extracts the IPv4 address that is embedded in the IPv6 destination address and encapsulates the IPv6 packet in an IPv4 packet with the extracted destination IPv4 address. The destination router extracts the IPv6 packet and forwards it to the IPv6 destination.
104
What is a 6to4 RD tunnel?
IPv6 Rapid Deployment (6RD) tunnels are an extension of 6to4 and allow a service provider to provide unicast IPv6 service to customers over its IPv4 network by using encapsulation of IPv6 in IPv4.
With 6RD, service providers do not have to use a 2002::/16 prefix; instead, they use a prefix from their own SP address block.
The IPv6 operational domain is within the SP’s networks.
A 6RD Border Relay (BR) is a 6RD-enabled router managed by the SP. A BR has an interface in the IPv6 network, another interface in the IPv4 network, and a virtual interface that is the endpoint for the 6RD IPv6-in-IPv4 tunnel.
105
T/F: With DNS64, when an IPv6 AAAA resource record (RR) is not available, DNS64 enables the DNS server to synthesize an AAAA record from an IPv4 A record.
True.
It allows an IPv6-only client to initiate communications by name to an IPv4-only server. The IPv6 address is generated based on the IPv4 address returned from the A record, an IPv6 prefix, and other parameters.
106
T/F: Stateful NAT64 multiplexes many IPv6 addresses into a single IPv4 address.
T/F: In NAT64 stateless translation, an IPv4 address is directly embedded into an IPv6 address.
True and True.
A limitation of stateless NAT64 translation is that it directly translates only the IPv4 options that have direct IPv6 counterparts, and it does not translate any IPv6 extension headers beyond the fragmentation extension header; however, these limitations are not significant in practice.
The state is created in the NAT64 device for every flow, and only IPv6-initiated flows are supported. There is no binding between an IPv6 address and an IPv4 address, as there is in stateless NAT64.
107
What are the following IPv6 addresses signifying?
2000::/3
FC00::/7
FEC0::/10
FE80::/10
FF00::/8
**2000::/3** - Global Unicast Address
**FC00::/7** - Unique local unicast, private address space of IPv6
**FEC0::/10** - Site local IPv6 address, like private ip blocks (deprecated)
**FE80::/10** - Link Local address, locally significant on segment (exist because there is no ARP and no Broadcast, so it configures it's own address on the local link. This begins with ND, then the router replies with a Router Advertisement that has network, gateway, etc. NOTE: next hop addresses are Link Local addresses because in order to get out of the link you need to connect to anotgher host on the network.
**FF00::/8** - Multicast addresses in IPv6
108
TF: A webserver can be assigned two IPv6 addresses, from two different ISPs for fault tolerance.
True.
Multihoming makes this possible.
109
What is the commands to configure SLAAC on an interface in a Cisco device?
interface# **ipv6 address autoconfig**
This will automatically configure a link local address on the interface. FE80::1234.56FF.FE78.9ABC
interface# **ipv6 address 2600:db8:dead:beef::/64 eui-64**
This will configure the IPv6 address:
2600:db8:dead:beef:1234.56FF.FE78.9ABC
110
True or false: OSPFv2 supports IPv6.
False. OSPFv3 supports IPv6. OSPFv2 is used in IPv4 networks.
111
True or false: DNS AAAA records are used in IPv6 networks for name-to-IPv6 address resolution.
True.
112
Fill in the blank: IPv6 ND is similar to _______ for IPv4 networks.
ARP.
113
How many bits are there between the colons in an IPv6 address?
16
114
The first field of the IPv6 header is 4 bits in length. What binary number is it always set to?
0110. The first field of the IPv6 header is the Version field. It is set to binary 0110 (6).
115
True or false: DHCP is required for dynamic allocation of IPv6 addresses.
False.
116
IPv6 multicast addresses begin with what hexadecimal prefix?
0xFF (1111 1111 binary).
117
IPv6 link-local addresses begin with what hexadecimal prefix?
FE8/10.
118
True or false: ISATAP allows tunneling of IPv6 through IPv4 networks.
True.
119
List the eight fields of the IPv6 header.
Version, Traffic Class, Flow Label, Payload Length, Next Header, Hop Limit, IPv6 Source Address, and IPv6 Destination Address.
120
True or false: The IPv6 address 2001:0:0:1234:0:0:0:abcd can be represented as 2001::1234:0:0:0:abcd and 2001:0:0:1234::abcd.
False. The longer set of zeros should be compressed. The valid representation is 2001:0:0:1234::abcd.
121
Which of the following is not an IPv6 address type?
1. Unicast
2. Broadcast
3. Anycast
4. Multicast
B. IPv6 address types are unicast, anycast, and multicast.
122
What is the subnet prefix of 2001:1:0:ab0:34:ab1:0:1/64?
2001:1:0:ab0::/64.
123
An IPv6 address has 128 bits. How many hexadecimal numbers does an IPv6 address have?
32.
124
What type of IPv6 address is FF01:0:0:0:0:0:0:2?
It is a multicast address. All IPv6 multicast addresses begin with hexadecimal FF.
125
What is the compact format of the address 2102:0010:0000:0000:0000:fc23:0100:00ab?
1. 2102:10::fc23:01:ab
2. 2102:001::fc23:01:ab
3. 2102:10::fc23:100:ab
4. 2102:0010::fc23:01:ab
C. Answers A, B, and D are incorrect because 0100 does not compact to 01. Answer B is also incorrect because 0010 does not compact to 001.
126
When using the dual-stack backbone, which of the following statements is correct?
1. The backbone routers have IPv4/IPv6 dual stacks, and end hosts do not.
2. The end hosts have IPv4/IPv6 dual stacks, and backbone routers do not.
3. Both the backbone routers and the end hosts have IPv4/IPv6 dual stacks.
4. Neither the backbone routers nor the end hosts have IPv4/IPv6 dual stacks.
A. The dual-stack backbone routers handle packets between IPv4 hosts and IPv6 hosts.
127
How does a dual-stack host know which stack to use to reach a destination?
1. It performs an ND, which returns the destination host type.
2. It performs a DNS request to return the IP address. If the returned address is IPv4, the host uses the IPv4 stack. If the returned address is IPv6, the host uses the IPv6 stack.
3. The IPv6 stack makes a determination. If the destination is IPv4, the packet is sent to the IPv4 stack.
4. The IPv4 stack makes a determination. If the destination is IPv6, the packet is sent to the IPv6 stack.
B. DNS indicates which stack to use. DNS A records return IPv4 addresses. DNS AAAA records return IPv6 addresses.
128
19. What protocol numbers are used by Ethernet to identify IPv4 versus IPv6?
1. Protocol 6 for IPv4 and protocol 17 for IPv6.
2. 0x86DD for IPv6 and 0x0800 for IPv4.
3. 0x8000 for IPv4 and 0x86DD for IPv6.
4. 0x0800 for both IPv4 and IPv6; they are identified in the packet layer.
B.
129
Which of the following is true of the IPv6 header? (Choose two.)
1. It is 40 bytes in length.
2. It is of variable length.
3. The Protocol Number field describes the upper-layer protocol.
4. The Next Header field describes the upper-layer protocol.
A and D.
130
21. Which of the following is true about fragmentation?
1. Routers between source and destination hosts can fragment IPv4 and IPv6 packets.
2. Routers between source and destination hosts cannot fragment IPv4 and IPv6 packets. \
3. Routers between source and destination hosts can fragment IPv6 packets only. IPv4 packets cannot be fragmented.
4. Routers between source and destination hosts can fragment IPv4 packets only. IPv6 packets cannot be fragmented.
D. IPv4 packets can be fragmented by the sending host and routers. IPv6 packets are fragmented by the sending host only.
131
A packet sent to an anycast address reaches what?
1. The nearest destination in a set of hosts
2. All destinations in a set of hosts
3. All hosts
4. Global unicast destinations
A. Anycast addresses reach the nearest destination in a group of hosts.
132
Which of the following is/are true about IPv6 and IPv4 headers?
1. The IPv6 header is of fixed length, and the Next Header field describes the upper-layer protocol.
2. The IPv4 header is of variable length, and the Protocol field describes the upper-layer protocol.
3. The IPv6 header is of fixed length, and the Protocol field describes the upper-layer protocol.
4. A and B
5. B and C
D.
133
An organization uses an IPv6 address range that it received from its ISP. The IPv6 addresses will be used internally, and employees will access the Internet by using Port Address Translation. What is required for DNS?
1. DNS servers need to support only IPv4 addresses.
2. DNS servers need to support only IPv6 addresses.
3. No changes are needed to the DNS servers.
4. DNS servers need to support both IPv4 and IPv6 addresses.
5. Additional DNS servers for IPv6 addresses are needed.
6. DNS servers are not needed for PAT.
D.
134
Which statements about IPv6 addresses are true? (Choose two.)
1. Leading 0s are required.
2. Two colons (::) are used to separate fields.
3. Two colons (::) are used to represent successive hexadecimal fields of 0s.
4. A single interface can have multiple IPv6 addresses of different types.
C and D.
135
You have duplicate file servers at multiple locations. Which IPv6 address type allows each end station to send a request to the nearest file server using the same destination address, regardless of the location of that end station?
1. Anycast
2. Broadcast
3. Unicast
4. Global unicast
5. Multicast
A.
136
Which strategy allows both IPv4 and IPv6 addressing/stacks to coexist on a host and over time facilitate a transition to an IPv6-only network?
1. Deploy NAT64 between the networks.
2. Have hosts run IPv4 and routers run native IPv6.
3. Enable anycast in the routing protocol.
4. Deploy both IPv4 and IPv6 address stacks.
5. Redistribute between the IPv4 and IPv6 networks.
D.
137
Which strategy would be most flexible for a corporation with the following characteristics?
* 2,400,000 hosts
* 11,000 routers
* Internet connectivity
* High volume of traffic with customers and business partners
1. Deploy NAT64 between the business and Internet networks.
2. Have hosts run IPv4 and routers run native IPv6.
3. Have both hosts and routers run dual-stack.
4. Enable anycast in the routing protocol.
5. Redistribute between the IPv4 and IPv6 networks.
C. Running dual-stack IPv4 and IPv6 on hosts and routers allows for full flexibility for communications for the corporation internally, with partners, and with the Internet.
138
What is the hierarchy for IPv6 aggregatable addresses?
1. Global, site, loop
2. Public, site, interface
3. Internet, site, interface
4. Multicast, anycast, unicast
B.
139
NAT-PT translates between what address types?
1. RFC 1918 private addresses and public IPv4 addresses
2. IPv4 and IPv6 addresses
3. Network addresses and IPv6 ports
4. Private IPv6 addresses and public IPv6 addresses
B.
140
In a network where IPv6 exists within an IPv4 network, which two strategies allow the two schemes to coexist? (Choose two.)
1. Translate between the protocols.
2. Have hosts run IPv4 and routers run native IPv6.
3. Encapsulate IPv6 packets into IPv4 packets.
4. Enable anycast in the routing protocol.
5. Redistribute between the IPv4 and IPv6 networks.
A and C.
141
Which statement best describes the efficiency of the IPv6 header?
1. It is less efficient than the IPv4 header.
2. It has the same efficiency as the IPv4 header; the larger IPv6 address makes it faster.
3. It is more efficient than the IPv4 header.
4. It is larger than the IPv4 header.
C.
142
Which IPv6 feature enables routing to distribute connection requests to the nearest content server?
1. Anycast
2. Link-local
3. Aggregatable
4. Multicast
5. Site-local
A.
143
What of the following provides one-to-nearest communication for IPv6?
1. Anycast
2. Broadcast
3. Multicast
4. Unicast
A.
144
Which tunneling protocol allows dual-stack hosts to tunnel over an IPv4 network that is not multicast enabled?
1. 6to4
2. 6over4
3. IPsec
4. ISATAP
D
145
How would you summarize the following networks?
* 2001:0db8:2a3e:4490::/64
* 2001:0db8:2a3e:4a1b::/64
* 2001:0db8:2a3e:4ff2::/64
* 2001:0db8:2a3e:4c5b::/64
1. 2001:0db8:2a3e:4000::/52
2. 2001:0db8:2a3e:4000::/56
3. 2001:0db8:2a3e:4000::/60
4. 2001:0db8:2a3e:4000::/64
A. All the networks can be summarized with a 52-bit mask.
146
Which statement is true of IPv6 address assignment?
1. You should configure devices manually using IPv6 address assignment.
2. You should configure servers using SLAAC.
3. You should use SLAAC to assign IPv6 addresses and then DHCPv6 to assign additional information to hosts.
4. You cannot use DHCPv6 after a host is assigned an IPv6 address via SLAAC.
C. SLAAC is used first to assign the IPv6 address, and then DHCPv6 is used to assign additional options.
147
Which IPv6 feature allows a single node to send packets that are routed to the nearest receiver from a group of potential receivers?
1. Link-local
2. Site-local
3. Anycast
4. Multicast
C. Link-local and site-local addresses are unicast addresses, and multicast addresses are sent to a group of hosts. Anycast addresses are routed to the nearest receiver from a group of hosts.
148
Which statement is correct?
1. IPv6 does not use multicast addresses.
2. IPv6 routers do not forward a packet that has a link-local source address.
3. DHCPv6 is the only method for dynamic address assignment.
4. IPv6 routers forward a packet that has a link-local destination address.
B. A packet with a link-local source address remains with the local link.
149
Which two link-state routing protocols support IPv6 routing? (Choose two.)
1. RIPng
2. OSPF
3. EIGRP
4. IS-IS
5. BGP4+
B and D. Only OSPF and IS-IS are link-state routing protocols.
150
Which are transition strategies to IPv6 for an enterprise network? (Choose three.)
1. Dual-stack
2. Top-down
3. Tunneled
4. Merge
5. Translation
6. Fork-lift
7. Hybrid
A, C, and E. Dual-stack, tunneled, and translation are strategies for transitioning to IPv6.
151
How can an ISATAP packet be identified?
1. The FF05/64 prefix is used.
2. The fifth and sixth 16-bit words are 0000:5EFE.
3. The 2002::/16 prefix is used.
4. The FE80:/10 prefix is used.
B. ISATAP uses a well-defined IPv6 address format composed of any unicast prefix of 64 bits, which can be a link-local or global IPv6 unicast prefix. It then uses the 32 bits 0000:5EFE that define the ISATAP address ending with the 32-bit IPv4 address of the ISATAP link.
152
If an application uses broadcast traffic for IPv4, how will it communicate using IPv6?
1. Anycast
2. Broadcast
3. Multicast
4. Unicast
C. IPv6 multicast “all-nodes” addresses replace IPv4 broadcasts.
153
What type of address begins with the prefix FC00::/?
1. Local-link
2. Broadcast
3. Multicast
4. Unique local unicast
D. Unique local unicast IPv6 addresses use the FC00::/7 prefix.
154
Which IPv6 migration strategy is recommended if only a few IPv6 clients need to access network servers that support only IPv4?
1. IPv4-mapped IPv6 addresses
2. IPv6 over IPv4 GRE tunnels
3. NAT64
4. 6PE
C. NAT64 is a transition mechanism that does translation where the IPv6 client can reach IPv4-only servers.
155
Which is the correct representation of 2001:004C:0000:0000:9A:0000:0000:0001?
1. 2001:4C::9A::1
2. 2001:4C:0:0:9A::1
3. 2001:4C:0:0:9A::1
4. 2001:4C::9A:0:0:1
D. 2001:4C::9A:0:0:1 is the correct representation since the first set of 16-bit pairs is the set that should be compressed.
156
Which type of IPv6 address is ::FFFF:AA11/96?
1. Global unicast address
2. Link local address
3. IPv4-compatible IPv6 address
4. IPv4-mapped IPv6 address
D.::FFFF:0:0/96 addresses are IPv4-mapped IPv6 addresses. 2000::/3 addresses are global unicast addresses, FE80::/10 addresses are link local addresses, and 0000::/96 addresses were IPv4-compatible IPv6 addresses that have been deprecated.
157
Which translation mechanism is recommended to support flow-based translations for multiple IPv6 devices to a single IPv4 address?
1. NAT4to6
2. Stateful NAT46
3. Stateful NAT64
4. Stateless NAT64
C. Stateful NAT64.
158
Which tunnel solution allows an SP to provide IPv6 unicast service to its customers?
1. GRE tunnels
2. 6RD tunnels
3. 6to4 tunnels
4. ISATAP tunnels
B. 6RD tunnels allow an SP to provide unicast IPv6 service to its customers over its IPv4 network.
159
What does a DNS64 server do if an IPv6 AAAA record is returned empty?
1. Query the IPv4 DNS authoritative server.
2. Query the IPv6 DNS authoritative server.
3. Query the NAT64 server.
4. Drop the packet since there is an IPv6 address.
A. If an AAAA query is returned empty, the DNS64 server queries the IPv4 DNS authoritative server for an A record.
160
An enterprise network designer wants to use the WKP 64:ff9b::/96 for NAT64 to reach servers outside the organization. Is this a viable solution?
1. Yes, the NAT64 WKP 64:ff9b::/96 provides a globally unique solution.
2. No, the NAT64 WKP 64:ff9b::/96 is not a globally routable prefix.
3. Yes, define a NAT64 NSP.
4. No, use the NAT WKP 2001:FF9b::/96 instead.
5. Answers B and C are correct.
6. Answers C and D are correct.
E. Both answers B and C are correct. The WKP 64:ff9b::/96 is not globally routable, and an NSP needs to be defined. 2001:FF9b::/96 is not a NAT64 WKP.
The NAT64 prefix can be a Network-Specific Prefix (NSP) which is assigned to a provider and chosen by the network administrator or a **Well-Known Prefix (WKP) defined by IETF as 64:ff9b::/96** to represent IPv4 addresses in IPv6 namespace (i.e. an IPv4-converted IPv6 address).
161
See attached Figure 2-18.
* A company has an existing WAN that uses IPv4. Sites C and D use IPv4. As shown in Figure 2-18, the company plans to add two new locations (Sites A and B). The new sites will implement IPv6. The company does not want to lease more WAN circuits.
What options does the company have to connect Site A to Site B?
Implement a dual-stack backbone or implement IPv6 over IPv4 tunnels.
162
See attached Figure 2-18.
* A company has an existing WAN that uses IPv4. Sites C and D use IPv4. As shown in Figure 2-18, the company plans to add two new locations (Sites A and B). The new sites will implement IPv6. The company does not want to lease more WAN circuits.
What mechanism needs to be implemented so that IPv6 hosts can communicate with IPv4 hosts and vice versa?
NAT64 is used to provide translation between IPv6 and IPv4 hosts.
163
See attached Figure 2-18.
* A company has an existing WAN that uses IPv4. Sites C and D use IPv4. As shown in Figure 2-18, the company plans to add two new locations (Sites A and B). The new sites will implement IPv6. The company does not want to lease more WAN circuits.
If a dual-stack backbone is implemented, do all WAN routers and all hosts need an IPv6/IPv4 dual stack?
If a dual-stack backbone is implemented, only the WAN routers require an IPv6/IPv4 dual stack. End hosts do not need a dual stack.
164
See attached Figure 2-18.
* A company has an existing WAN that uses IPv4. Sites C and D use IPv4. As shown in Figure 2-18, the company plans to add two new locations (Sites A and B). The new sites will implement IPv6. The company does not want to lease more WAN circuits.
If an IPv4 tunnel is implemented between Sites A and B, do all WAN routers require an IPv6/IPv4 dual stack?
No. All WAN routers still run the IPv4 stack, with two exceptions: the WAN routers at Sites A and B. These routers speak IPv6 within their sites and speak IPv4 to the WAN.
165
The first two bytes of and IPv6 address have a lot of information. The first bytes is the FP, the Format Prefix. The third nibble is the flags field and the fourth nibble is called the Scope field.
What does the Scope field indicate? What are the following scopes?
1. 0001
2. 0002
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. In addition to information provided by multicast routing protocols, routers use the multicast scope to determine whether multicast traffic can be forwarded.
0 - Reserved
**1 - Node-local scope**
**2 - Link-local scope -** An IPv6 router never forwards this traffic beyond the local link.
5 - Site-local scope
8 - Organization-local scope
E - Global scope
F - Reserved
166
Multicast addresses from FF01:: through FF0F:: are reserved, well-known addresses.
What are these:
1. FF0**1**::1
2. FF0**2**::1
3. FF0**1**::2
4. FF0**2**::2
5. FF0**5**::2
**Group ID -** Identifies the multicast group and is unique within the scope. The size of this field is 112 bits. Permanently assigned group IDs are in-dependent of the scope. Transient group IDs are relevant only to a specific scope. Multicast addresses from FF01:: through FF0F:: are reserved, well-known addresses.
To identify all nodes for the node-local and link-local scopes, the following addresses are defined:
FF0**1**::1 (**node-local scope** all-nodes multicast address)
FF0**2**::1 (**link-local scope** all-nodes multicast address) (broadcast to all)
To identify all routers for the node-local, link-local, and site-local scopes, the following addresses are defined:
FF0**1**::2 (**node-local scope** all-routers multicast address)
FF0**2**::2 (**link-local scope** all-routers multicast address)
FF0**5**::2 (**site-local scope** all-routers multicast address)
IPv6 multicast addresses replace all forms of IPv4 broadcast addresses. The IPv4 network broadcast (in which all host bits are set to 1 in a classful environment), subnet broadcast (in which all host bits are set to 1 in a non-classful environment), and limited broadcast (255.255.255.255) addresses are replaced by the link-local scope all-nodes multicast address (FF02:01) in IPv6.
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What is the link local address range in IPv6? and IPv4?
Link-local addresses are not guaranteed to be unique beyond their network segment, therefore routers do not forward packets with link-local source or destination addresses.
In IPv6, they are assigned from the block fe80::/10
IPv4 link-local addresses are assigned from address block 169.254.0.0/16 (169.254.0.0 through 169.254.255.255).
