NCTI 2023 with verified questions and answers

Question Answer What was the primary driver for development of IPv6? To address the issue of IPv4 address exhaustion. When comparing IPv4 to IPv6, which of the following statements is true IPv4 uses a 32-bit address scheme, while IPv6 uses a 128-bit address scheme. In IPv6-enabled networks, static addressing is no longer allowed. FALSE Without IPv4's network address translation (NAT), IPv6 offers simpler packet construction and better support for peer-to-peer and mobile-to-mobile types of communications. TRUE In IPv6, Quality of Service (QoS) is radically changed, utilizing only the flow label for all QoS provisioning. FALSE Unfortunately, only RIP (Routing Information Protocol) and OSPF (Open Shortest Path First) are capable of routing IPv6. FALSE What size are IPv4 and IPv6 addresses, respectively? 32-bits, 128-bits. IPv4 addresses are written in dotted-decimal. Which of these best describes how IPv6 addresses are written? Hexadecimal notation, dropping leading zeros in each hextet, using the "::" notation to represent missing all-zero hextets. IPv6 addresses are written in Binary Coded Decimal (BCD). FALSE An example of a single 16-bit "hextet" in an IPv6 address could be shown like this: :54a2:. What is an "IID"? Interface Identifier. How large is a typical user-centric IPv6 subnet size, for a single subnet, using CIDR notation? /64 What does the notation "2000::/3" mean, in terms of the initial IETF allocation for IPv6 global unicast space? That global unicast addresses always start with the first three bits "001" (first 3 bits of the address per the "/3" notation). Which of these prefix lengths would be a reasonable assignment for a service provider? /32 Which of these prefix lengths would be a reasonable assignment for a small single-homed commercial enterprise with no more than 15 or 20 networks? /48. What is a unique aspect of an "anycast" address? It is an address typically assigned to more than one interface, typically on different nodes. The leftmost 64-bits of an IPv6 unicast address typically describe: The location in the IPv6 routing hierarchy of a particular subnet. The rightmost 64-bits of an IPv6 unicast address typically describe: The specific interface on the subnet. The main types of IPv6 addresses are: Unicast, anycast, and multicast. What does the term "ULA" mean? Unique Local Addresses. The function of Unique Local Addresses are: For use within a network enclave, and not routed or announced to the public Internet. Link-local addresses come from which part of the IPv6 address space? FE8::/10. IPv6 Multicast addresses always fall within what prefix? FF00::/8. What kind of unicast address does every IPv6 interface have to have? Link-local. EUI-64 construction includes a unique marker for what purpose? A bit within the IID (rightmost 64-bits) set to indicate the IID was built from a globally-unique token. The scope over which link-local IPv6 addresses must be unique is: On the link where the interface is configured. In the multicast address FF02::1, the "0" describes: The "flags" for the address. Which is an example of an IPv6 multicast address that a router would normally listen for? FF02::1 (all nodes multicast, interface scope). Which IPv6 multicast address does a DHCPv6 server listen on? FF05::1:3. Which of these is a key difference between the IPv4 packet structure and the IPv6 packet structure? The IPv6 base header is fixed length, whereas the IPv4 header is variable length. The IPv6 base header has fewer fields than the IPv4 header. Which of the following names two of the missing fields correctly? Header Length (HL) and "Header Checksum" fields. n IPv4 header has fewer fields than an IPv6 base header. FALSE What is the difference between IPv4's "Total Length" field and IPv6's "Payload Length" field? Total Length is the full length of the packet, including the IPv4 header, and "Payload Length" is the size of any IPv6 extension headers (if present) and L4 segment combined (if present). The IPv4 header field "Time to Live" field is renamed in the IPv6 base header, but the function of the field is identical. What is the new name? Hop Limit. What are the lengths of the IPv6 base header and the IPv4 header? 40 bytes and "variable" (the IPv4 header is of variable size). The IPv6 base header contains one entirely new field, what is the name of the field? Flow-Label. A set of fields contained in the IPv4 header are not present in the IPv6 base header, but moved to an IPv6 extension header, which are they? Identification and Fragment Offset. What does a value of "60" in the base header's "Next Header" field indicate? The value 60 in the base header's Next Header field indicates that a destination options extension header follows. Under what conditions is a Fragmentation Extension Header attached to a packet? When an IPv6 packet is too large for any L2 segment on the path to the destination. IPv6 packets always carry at least one IPv6 extension header. FALSE IPv6 allows "piggybacking" multiple L4 segments into a single IPv6 packet (such as multiple TCP segments, or a TCP segment and UDP segment). FALSE What does the acronym "TLV" mean in terms of IPv6 extension header options? Type-Length-Value. What nodes examine the Hop-by-Hop extension header on the path between the source and destination nodes? The source, all intermediate nodes, and the ultimate destination node. What nodes examine the Destination Options extension header on the path between the source and destination nodes? The source and the ultimate destination node only. IPsec is implemented in IPv6 using extension headers, what are their names? Authentication Header (AH) and Encapsulating Security Payload (ESP). The base IPv6 specification requires IPv6 stacks to support the IPsec AH and ESP functions. TRUE IPv6 has an extension header called "No Next Header," which is used in an IPv6 base header or IPv6 extension header to indicate that there is no next header. TRUE Which of the following is true? IPv6 has a more flexible and extensible packet format than IPv4 because of the IPv6 extension header construct. What newer protocol, developed after IPv6 was standardized, illustrates the flexibility and extensibility of the IPv6 protocol? Mobile IPv6 (MIPv6). IPv6 uses extension headers to support special packet services. Which of the following statements most accurately describes the scenario where multiple extension headers are in use? The IPv6 base header, and each extension header, carries the "Next Header" field which indicates the type of header that follows. Which of the following is an IPv6 function implemented using ICMPv6? Neighbor Discovery, via NS/NA exchanges. In IPv6, what happens if a node receives a data packet that is "too big" to forward to other nodes? The source node receives a "too big" packet error, which includes the first portion of the original packet that caused the error message, assisting the source in determining which packet was too large. Which of these messages is an ICMPv6 message? Destination Unreachable. Which ICMPv6 error message is sent by an intermediate router, on the path between source and destination interface, when the base header "Hop Limit" field is counted down to zero? Time Exceeded (Hop Limit Exceeded). What ICMPv6 message is sent when an intermediate or destination node cannot understand an IPv6 packet's header field, next header value, or IPv6 option? Parameter Problem. What node sends the ICMPv6 error message with the code set to "fragment reassembly time exceeded", which tells the source node that all packet fragments received have been discarded? The intermediate router where the error occurred. When a source node first sends packets to a new destination address, the source first sends "Path MTU Exploration Packets" (PMTU-E), in advance of really starting to send the session data itself, to test and discover the Path MTU. FALSE IPv6-capable routers often advise on-link hosts of the on-link prefixes, and other information, using which ICMPv6 message? Router Advertisement (RA). IPv6 hosts, upon first joining a link and initializing an interface, send which of the following ICMPv6 messages immediately after configuring a TENTATIVE IPv6 address, in order to run the Duplicate Address Detection (DAD) process: Neighbor Solicitation (NS). To find a router on the local subnet, via a Router Solicitation (RS), what destination IPv6 address is the RS sent to by the host? All-routers-multicast (ff02::2). When a router sends an on-link host a redirect, what information does the redirect contain? Information that the source host uses to plumb a host route via a different router for the target (destination in question) such that subsequent packets to that destination transit via a better first-hop router. Neighbor Discovery, via the exchange of Neighbor Solicitation and Neighbor Advertisement messages, is used by IPv6 similarly to what non-ICMP-based IPv4 process? Address Resolution Protocol (ARP). Neighbor Discovery, via the exchange of Neighbor Solicitation and Neighbor Advertisement messages, is used by IPv6 similarly to what non-ICMP-based IPv4 process? Via RA messages being sent by the router. IPv6 uses ICMPv6 and the Router Solicitation (RS) and Router Advertisement (RA) exchange to implement what process? Stateless Address Autoconfiguration (SLAAC). What is the "Solicited Node Multicast Address"? The destination multicast address to which Neighbor Solicitation packets are sent when one node is trying to learn the L2 address for another node with a given IPv6 address. ICMPv6 Neighbor Discovery is functionally equivalent to IPv4's "ARP" process, and also uses discovery messages sent to the IPv6 broadcast address, to which all IPv6 nodes are listening. FALSE What happens to the Neighbor Discovery process if two interfaces on the same link are identical in the low 24-bits of the Interface ID (IID), but different in the other bits of the IID? Neighbor Discovery is successful anyway. Router Advertisements (RAs) are always sent from a link-local address. TRUE What is one key reason the IPv6 ICMPv6 NS/NA process is more efficient on the network than the corresponding IPv4 "ARP" process? NS discovery packets are sent via multicast, rather than ARP-request packet's which are broadcast What device generates the Internet control message protocol version 6 (ICMPv6) Destination Unreachable error message? The device that is unable to forward the packet to its original destination. How long will a router advertisement (RA) containing two prefix information options (PIO), one valid and preferred (the new prefix), and one valid but not preferred (the old prefix) be recognized by a host? Until all previously-started, in-flight RA sessions using the PIO being retired have completed naturally. Suppose an IPv6 node receives a packet where it does not recognize the "Next Header" value in the IPv6 base header. Which of the following is true regarding the node's ability to process the packet? The packet can NOT be processed, because the node cannot decode a packet if it does not know which protocol is carried after the IPv6 base header. When a Router Advertisement (RA) has the O bit set within the prefix information option (PIO), what does that mean to the host? Advised to perform Other DHCPv6 process, attempt to get stateless parameters What roles can DHCPv6 play in an IPv6 deployment? Stateful address assignment, and/or stateless parameter assignment, and/or prefix delegation. Which of the following parameters can DHCPv6 client requests obtain? Caching DNS server addresses. The three pieces that make up a DHCPv6 "system" are: Client, relay, and server. One important difference between DHCPv4 and DHCPv6 operations is: DHCPv6 client uses multicast-based SOLICIT, DHCPv4 client uses broadcast-based Discover. DHCP relays are never needed in large IPv6 deployments, because the DHCPv6 client discovers the DHCPv6 server via a well-known organizational-scoped multicast (ff18::700) directly. FALSE What does the term DUID stand for? DHCP Unique Identifier. How do DHCPv6 and Stateless Address Autoconfiguration (SLAAC) relate? DHCPv6 can do stateful address assignment, whereas SLAAC is a router-based solution to allow interfaces to configure their own address when advertised a prefix. There is a capability within a Router Advertisement for the RA (RA) to include advice to the host about whether or not to use DHCPv6, and what "DHCPv6 mode" to use. TRUE When a Router Advertisement (RA) has the "M" bit set, what does that mean to the host? Advised to perform "Managed" DHCPv6 process; attempt to get stateful IPv6 address. DHCPv6 runs over IPv6/TCP, where DHCP for IPv4 runs directly over Layer 2 (normally Ethernet). FALSE DHCPv6 is completely backwards-compatible with existing IPv4 DHCPv4 clients. FALSE What problem does DHCPv6-PD solve? Allows CPE router to obtain IPv6 prefix for internal use across multiple segments. What is the best term for the IPv6 forward addressing records in DNS? Quad-A records. Which of the following is a valid IPv6 forward addressing record? Athens-pc AAAA 2001::300 What boundaries are IPv6 PTR records written on? Nibble (4-bit) boundaries. IPv4 reverse records are called "PTR" records. What are IPv6 reverse records called? B) PTR records. When a DNS server is said to be "IPv6-capable", one of two (or both) unrelated capabilities could be meant, and should be clarified. What are the two capabilities Ability to understand and respond to IPv6 record types, and ability to receive queries and transmit answers over IPv6 transport. What component in the DNS hierarchy does the host/client-based resolver library talk to? Caching DNS server. IPv6 uses the same major DNS hierarchy (DNS client, caching server, authoritative server, and root server elements) as does "traditional" IPv4 DNS. TRUE One significant weakness in the DNS posture today in terms of IPv6 support is the lack of any IPv6 addresses in the root server "hints" file. FALSE What is the ideal posture for an authoritative, Internet-facing DNS server today? Dual-stack capable. Routes learned via one protocol may be advertised onward by another routing protocol, describes which IPv6 routing method? ... Which of the following routing protocols is multiprotocol? Intermediate System to Intermediate System (IS-IS). What is a standards-required feature of IPv6 static routing that is "new" as compared to IPv4 static routing? ... Conceptually, Policy-Based Routing (PBR) and Route Redistribution are very similar for IPv4 and IPv6. TRUE With regards to the pace at which organizations adopt IPv6, the lesson suggests that: Enterprises will transition slowly while service providers will adopt IPv6 more quickly. The three main categories of IPv6 transition tools are: Dual-stack, tunneling, translation. When a device is "dual-stacked" it has which configuration? The network interface is configured for both IPv4 and IPv6. What is the key advantage and disadvantage of dual-stack? Dual-stack is architecturally simple, but impacts large portion of infrastructure. In terms of IPv6 transition, what does tunneling refer to? The encapsulation of IPv6 in IPv4. What are the two types of IPv6 tunnels? Manual and Automatic. What is IPv6 tunneling's biggest advantage? Cost savings by enabling use of IPv4-only gear. Which of the following statements is true IPv4 and IPv6 do not interoperate. With regards to translation and IPv6, which of the following is the most correct statement? Translation is the least desirable method for IPv6 transition. IPv6 performs fragmentation so differently from IPv4, including the "no intermediate fragmentation rule", that end-host vulnerability to fragmentation-based attacks are effectively eliminated in IPv6. FALSE What are the three categories of Layer 3 (Network Layer) attacks? Reconnaissance, access, and denial of service (DoS). Which of these is a vulnerability resulting from the IPv6 extension header construct? Router resource consumption attacks from overuse of extension headers in IPv6 packets. What method do IPv4 and IPv6 nodes use to mitigate the security vulnerability of "eavesdropping"? IPv4 and IPv6 use Internet protocol security (IPsec). One significant difference between IPv4 and IPv6 security, in terms of scanning subnets looking for active hosts, is Because IPv6 subnets are so large (/64), it is much more difficult for brute-force scanning attacks to quickly find active interfaces on a subnet. IPv6, because of its unique operations compared to IPv4, provides an effective security protection against transmission control protocol (TCP) stack overflow attacks FALSE Because IPv6 does not have the same "Options" field in the base header that IPv4 does, processor-based attacks on IPv6 packets meant to push packets to the software path, rather than have them forwarded in hardware, is not an effective attack in IPv6. FALSE By eliminating network address translation (NAT) client devices that were previously masked within a private address scheme in IPv4, are at risk of being identified by systems outside of the private network. What can be used in IPv6 to mitigate this risk? IPv6 Privacy Addressing. Which of the following statements is most true with regards to use of Teredo in managed environments? It should be managed through engineered & security managed solutions. Which of these statements most accurately reflects the sentiments about IPv4 and IPv6 security? IPv4 and IPv6 security measures are roughly the same.