Cisco Certified Support Technician (CCST) Networking 100-150 Practice Test 31
Question 300
Before approving the action, review: At the fictional Elmwood Guesthouse after a user reports a recurring problem, the team observes: A technician assumes an IPv6 /64 has a 64-bit address in total rather than a 128-bit address with a 64-bit prefix. During “Explain the /64 split between network prefix and interface identifier for the example subnet.”, which precaution MOST specifically prevents a related risk?
- Do not classify public DNS destinations as internal RFC 1918 hosts.
- Do not count the all-host-zero network or all-host-one broadcast address as an ordinary host.
- Do not reduce an IPv6 address's total length to its prefix length.
- Do not give LAN clients 127.0.0.1 as the address of a separate host.
Explanation
Correct Answer
C:Correct. This precaution prevents a second fault while applying “Explain the /64 split between network prefix and interface identifier for the example subnet.” at the fictional Elmwood Guesthouse. The required protection is “Do not reduce an IPv6 address's total length to its prefix length.”; success still requires “The annotation correctly allocates 64 bits to each part of the 128-bit address.”.
Incorrect Answers
A:This caution is appropriate for a separate failure pattern: A network drawing marks 8.8.8.8 and 192.168.1.10 as the same address-scope type for internet routing. The principal adjacent risk here is controlled by “Do not reduce an IPv6 address's total length to its prefix length.”.
B:This caution is appropriate for a separate failure pattern: A site requests at least 50 usable IPv4 addresses and the trainee chooses a /27 because 32 looks close to 50. The principal adjacent risk here is controlled by “Do not reduce an IPv6 address's total length to its prefix length.”.
D:This caution is appropriate for a separate failure pattern: A developer uses 127.0.0.1 as the server address in an application deployed to other PCs on the LAN. The principal adjacent risk here is controlled by “Do not reduce an IPv6 address's total length to its prefix length.”.
Question 301
A technician reviews the following issue: At the fictional Northpoint Library during a physical cabling audit, the team observes: An IPv6 client has ::1 and the engineer tries to use it as the next-hop router address. Which action MOST directly resolves the reported issue?
- Determine the network as 172.16.8.0 and broadcast as 172.16.9.255.
- Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.
- Use the configured /27 prefix and corresponding mask for the subnet calculation.
- Apply 255.255.255.224 and recalculate the subnet's network and broadcast boundaries.
Explanation
Correct Answer
B:Correct. In the fictional Northpoint Library case, IPv6 ::1 is loopback on the local host rather than a remote default gateway. The specified corrective action, “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.”, directly targets that condition. Evidence of resolution: The client reaches its router using a nonloopback interface address and ::1 still tests itself.
Incorrect Answers
A:That action addresses a different network issue: A workstation is configured as 172.16.9.34/23 but the operator assumes 172.16.9.0 is the network ID. The present fictional Northpoint Library finding instead needs “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.”, verified by “The client reaches its router using a nonloopback interface address and ::1 still tests itself.”.
C:That action addresses a different network issue: A trainee is told an old Class C IPv4 label requires a /24 mask even though a configured interface explicitly uses /27. The present fictional Northpoint Library finding instead needs “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.”, verified by “The client reaches its router using a nonloopback interface address and ::1 still tests itself.”.
D:That action addresses a different network issue: An admin converts /27 to a mask of 255.255.255.0 and allocates too many clients to a tiny segment. The present fictional Northpoint Library finding instead needs “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.”, verified by “The client reaches its router using a nonloopback interface address and ::1 still tests itself.”.
Question 302
An incident reviewer analyzes this observation: At the fictional Northpoint Library during a physical cabling audit, the team observes: An IPv6 client has ::1 and the engineer tries to use it as the next-hop router address. What is the MOST specific underlying cause?
- IPv6 ::1 is loopback on the local host rather than a remote default gateway.
- Duplicate IPv4 host addresses on the same broadcast segment can cause ARP conflicts and loss of stable delivery.
- A /27 prefix corresponds to mask 255.255.255.224, yielding blocks of 32 addresses.
- A /27 contains only 32 total IPv4 addresses and 30 conventional usable hosts; /26 provides 62 usable.
Explanation
Correct Answer
A:Correct. This mechanism fits the observed network symptom at the fictional Northpoint Library: IPv6 ::1 is loopback on the local host rather than a remote default gateway. The corresponding remedy is “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.”. Confirmation: The client reaches its router using a nonloopback interface address and ::1 still tests itself.
Incorrect Answers
B:That cause belongs to a different case: An office assigns the same IPv4 address to a router interface and a server on one VLAN and the pair has intermittent reachability. The observed fictional Northpoint Library condition is specifically explained by “IPv6 ::1 is loopback on the local host rather than a remote default gateway.”.
C:That cause belongs to a different case: An admin converts /27 to a mask of 255.255.255.0 and allocates too many clients to a tiny segment. The observed fictional Northpoint Library condition is specifically explained by “IPv6 ::1 is loopback on the local host rather than a remote default gateway.”.
D:That cause belongs to a different case: A site requests at least 50 usable IPv4 addresses and the trainee chooses a /27 because 32 looks close to 50. The observed fictional Northpoint Library condition is specifically explained by “IPv6 ::1 is loopback on the local host rather than a remote default gateway.”.
Question 303
After an approved correction, the support team reviews: At the fictional Northpoint Library during a physical cabling audit, the team observes: An IPv6 client has ::1 and the engineer tries to use it as the next-hop router address. The approved corrective action is: “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.” Which result BEST demonstrates success?
- The endpoint can ARP for the gateway and reach an off-subnet test host.
- The printer uses a valid host IP and neither the network nor broadcast address is allocated to equipment.
- Manual subnet calculation matches a trusted calculator for the /23 address.
- The client reaches its router using a nonloopback interface address and ::1 still tests itself.
Explanation
Correct Answer
D:Correct. This is the required observable acceptance evidence for “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.” at the fictional Northpoint Library. It demonstrates correction of the original cause: IPv6 ::1 is loopback on the local host rather than a remote default gateway.
Incorrect Answers
A:That result is evidence for a separate corrective action, “Configure a default gateway address within the workstation's 192.168.60.0/26 subnet.”. It does not establish the intended outcome “The client reaches its router using a nonloopback interface address and ::1 still tests itself.” for the fictional Northpoint Library case.
B:That result is evidence for a separate corrective action, “Assign the printer one of 10.8.12.73 through 10.8.12.78 instead.”. It does not establish the intended outcome “The client reaches its router using a nonloopback interface address and ::1 still tests itself.” for the fictional Northpoint Library case.
C:That result is evidence for a separate corrective action, “Determine the network as 172.16.8.0 and broadcast as 172.16.9.255.”. It does not establish the intended outcome “The client reaches its router using a nonloopback interface address and ::1 still tests itself.” for the fictional Northpoint Library case.
Question 304
Before approving the action, review: At the fictional Northpoint Library during a physical cabling audit, the team observes: An IPv6 client has ::1 and the engineer tries to use it as the next-hop router address. During “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.”, which precaution MOST specifically prevents a related risk?
- Do not use the broader /24 network address when the configured interface is /25.
- Do not count the all-host-zero network or all-host-one broadcast address as an ordinary host.
- Do not set ::1 as the next-hop address for another network device.
- Do not replace a documented CIDR prefix with a historical classful default.
Explanation
Correct Answer
C:Correct. This precaution prevents a second fault while applying “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.” at the fictional Northpoint Library. The required protection is “Do not set ::1 as the next-hop address for another network device.”; success still requires “The client reaches its router using a nonloopback interface address and ::1 still tests itself.”.
Incorrect Answers
A:This caution is appropriate for a separate failure pattern: A workstation uses 192.168.10.130/25 and the help desk claims its subnet network address is 192.168.10.0. The principal adjacent risk here is controlled by “Do not set ::1 as the next-hop address for another network device.”.
B:This caution is appropriate for a separate failure pattern: A site requests at least 50 usable IPv4 addresses and the trainee chooses a /27 because 32 looks close to 50. The principal adjacent risk here is controlled by “Do not set ::1 as the next-hop address for another network device.”.
D:This caution is appropriate for a separate failure pattern: A trainee is told an old Class C IPv4 label requires a /24 mask even though a configured interface explicitly uses /27. The principal adjacent risk here is controlled by “Do not set ::1 as the next-hop address for another network device.”.
Question 305
A technician reviews the following issue: At the fictional Alderstone Dental Office during a scheduled lab validation, the team observes: A student expands 2001:db8::5 into an address with two separate :: compression markers and too many hextets. Which action MOST directly resolves the reported issue?
- Calculate the /25 network by masking the last octet and choose 192.168.10.128 as the network ID.
- Expand 2001:db8::5 into eight hextets with the correct number of zero groups.
- Keep the private prefix internally and arrange approved NAT or public address allocation at the network edge.
- Recognize the shared address scope and confirm carrier NAT or dedicated public access requirements.
Explanation
Correct Answer
B:Correct. In the fictional Alderstone Dental Office case, IPv6 :: compression represents a contiguous run of zero 16-bit groups and may appear only once in one address. The specified corrective action, “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.”, directly targets that condition. Evidence of resolution: The expanded address contains exactly eight 16-bit groups and round-trips to the short form.
Incorrect Answers
A:That action addresses a different network issue: A workstation uses 192.168.10.130/25 and the help desk claims its subnet network address is 192.168.10.0. The present fictional Alderstone Dental Office finding instead needs “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.”, verified by “The expanded address contains exactly eight 16-bit groups and round-trips to the short form.”.
C:That action addresses a different network issue: A support analyst believes an internal 192.168.50.0/24 address can be made public solely by changing the router's default route. The present fictional Alderstone Dental Office finding instead needs “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.”, verified by “The expanded address contains exactly eight 16-bit groups and round-trips to the short form.”.
D:That action addresses a different network issue: A guest Wi-Fi laptop shows 100.70.4.9 on the carrier-facing status page and the technician treats it as a customer-owned public IPv4 for inbound hosting. The present fictional Alderstone Dental Office finding instead needs “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.”, verified by “The expanded address contains exactly eight 16-bit groups and round-trips to the short form.”.
Question 306
An incident reviewer analyzes this observation: At the fictional Alderstone Dental Office during a scheduled lab validation, the team observes: A student expands 2001:db8::5 into an address with two separate :: compression markers and too many hextets. What is the MOST specific underlying cause?
- IPv6 :: compression represents a contiguous run of zero 16-bit groups and may appear only once in one address.
- 8.8.8.8 is publicly addressed while 192.168.1.10 belongs to private RFC 1918 space.
- For 192.168.40.0/24, .0 is the network ID, .255 is the directed broadcast, and .1 is a valid host.
- In a /26, .18 is in 192.168.60.0–.63 while .126 is in a different subnet .64–.127.
Explanation
Correct Answer
A:Correct. This mechanism fits the observed network symptom at the fictional Alderstone Dental Office: IPv6 :: compression represents a contiguous run of zero 16-bit groups and may appear only once in one address. The corresponding remedy is “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.”. Confirmation: The expanded address contains exactly eight 16-bit groups and round-trips to the short form.
Incorrect Answers
B:That cause belongs to a different case: A network drawing marks 8.8.8.8 and 192.168.1.10 as the same address-scope type for internet routing. The observed fictional Alderstone Dental Office condition is specifically explained by “IPv6 :: compression represents a contiguous run of zero 16-bit groups and may appear only once in one address.”.
C:That cause belongs to a different case: A LAN router's 192.168.40.1/24 interface is documented as the segment broadcast destination rather than a valid host. The observed fictional Alderstone Dental Office condition is specifically explained by “IPv6 :: compression represents a contiguous run of zero 16-bit groups and may appear only once in one address.”.
D:That cause belongs to a different case: A remote endpoint uses 192.168.60.18/26 with gateway 192.168.60.126 and cannot leave its LAN. The observed fictional Alderstone Dental Office condition is specifically explained by “IPv6 :: compression represents a contiguous run of zero 16-bit groups and may appear only once in one address.”.
Question 307
After an approved correction, the support team reviews: At the fictional Alderstone Dental Office during a scheduled lab validation, the team observes: A student expands 2001:db8::5 into an address with two separate :: compression markers and too many hextets. The approved corrective action is: “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.” Which result BEST demonstrates success?
- The classification distinguishes private 172.20.14.8 from an address such as 172.40.14.8.
- The subnet calculator and manual bitmask agree on the 32-address block size.
- The capacity calculation shows 64 total addresses, 62 usable host addresses, and the reserved endpoints.
- The expanded address contains exactly eight 16-bit groups and round-trips to the short form.
Explanation
Correct Answer
D:Correct. This is the required observable acceptance evidence for “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.” at the fictional Alderstone Dental Office. It demonstrates correction of the original cause: IPv6 :: compression represents a contiguous run of zero 16-bit groups and may appear only once in one address.
Incorrect Answers
A:That result is evidence for a separate corrective action, “Apply the correct 172.16.0.0/12 private address boundary to the branch inventory.”. It does not establish the intended outcome “The expanded address contains exactly eight 16-bit groups and round-trips to the short form.” for the fictional Alderstone Dental Office case.
B:That result is evidence for a separate corrective action, “Apply 255.255.255.224 and recalculate the subnet's network and broadcast boundaries.”. It does not establish the intended outcome “The expanded address contains exactly eight 16-bit groups and round-trips to the short form.” for the fictional Alderstone Dental Office case.
C:That result is evidence for a separate corrective action, “Select a /26 block for a conventional single-subnet requirement of at least 50 hosts.”. It does not establish the intended outcome “The expanded address contains exactly eight 16-bit groups and round-trips to the short form.” for the fictional Alderstone Dental Office case.
Question 308
Before approving the action, review: At the fictional Alderstone Dental Office during a scheduled lab validation, the team observes: A student expands 2001:db8::5 into an address with two separate :: compression markers and too many hextets. During “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.”, which precaution MOST specifically prevents a related risk?
- Do not use a subnet's directed broadcast address as a normal device interface address.
- Do not use a /24 mask with a documented /27 prefix length.
- Do not insert multiple double-colon compressions into one IPv6 address.
- Do not point a normal endpoint at an unreachable gateway from a different local subnet.
Explanation
Correct Answer
C:Correct. This precaution prevents a second fault while applying “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.” at the fictional Alderstone Dental Office. The required protection is “Do not insert multiple double-colon compressions into one IPv6 address.”; success still requires “The expanded address contains exactly eight 16-bit groups and round-trips to the short form.”.
Incorrect Answers
A:This caution is appropriate for a separate failure pattern: A technician is given 10.8.12.72/29 and assigns .79 to a printer, assuming every number in the block is usable. The principal adjacent risk here is controlled by “Do not insert multiple double-colon compressions into one IPv6 address.”.
B:This caution is appropriate for a separate failure pattern: An admin converts /27 to a mask of 255.255.255.0 and allocates too many clients to a tiny segment. The principal adjacent risk here is controlled by “Do not insert multiple double-colon compressions into one IPv6 address.”.
D:This caution is appropriate for a separate failure pattern: A remote endpoint uses 192.168.60.18/26 with gateway 192.168.60.126 and cannot leave its LAN. The principal adjacent risk here is controlled by “Do not insert multiple double-colon compressions into one IPv6 address.”.
Question 309
A technician reviews the following issue: At the fictional Oakside Warehouse during basic configuration verification, the team observes: An engineer expects an IPv6 host to ARP for a neighbor's MAC address exactly as IPv4 does. Which action MOST directly resolves the reported issue?
- Keep the private prefix internally and arrange approved NAT or public address allocation at the network edge.
- Check neighbor solicitation and advertisement traffic for the IPv6 peer on the local link.
- Assign separate available host addresses and confirm unique ARP mappings.
- Keep the workstation on its private LAN and use approved address translation or a secure remote-access design at the edge.
Explanation
Correct Answer
B:Correct. In the fictional Oakside Warehouse case, IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol. The specified corrective action, “Check neighbor solicitation and advertisement traffic for the IPv6 peer on the local link.”, directly targets that condition. Evidence of resolution: The neighbor cache shows the resolved link-layer address after ICMPv6 discovery.
Incorrect Answers
A:That action addresses a different network issue: A support analyst believes an internal 192.168.50.0/24 address can be made public solely by changing the router's default route. The present fictional Oakside Warehouse finding instead needs “Check neighbor solicitation and advertisement traffic for the IPv6 peer on the local link.”, verified by “The neighbor cache shows the resolved link-layer address after ICMPv6 discovery.”.
C:That action addresses a different network issue: An office assigns the same IPv4 address to a router interface and a server on one VLAN and the pair has intermittent reachability. The present fictional Oakside Warehouse finding instead needs “Check neighbor solicitation and advertisement traffic for the IPv6 peer on the local link.”, verified by “The neighbor cache shows the resolved link-layer address after ICMPv6 discovery.”.
D:That action addresses a different network issue: A small-office PC uses 192.168.40.17 and a trainee proposes advertising it as a directly reachable address on the public internet. The present fictional Oakside Warehouse finding instead needs “Check neighbor solicitation and advertisement traffic for the IPv6 peer on the local link.”, verified by “The neighbor cache shows the resolved link-layer address after ICMPv6 discovery.”.
Question 310
An incident reviewer analyzes this observation: At the fictional Oakside Warehouse during basic configuration verification, the team observes: An engineer expects an IPv6 host to ARP for a neighbor's MAC address exactly as IPv4 does. What is the MOST specific underlying cause?
- IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol.
- With a /24 mask their network prefixes are different and communication normally needs Layer 3 forwarding.
- Public addressing requires a legitimately assigned routable prefix or translation, not only an outbound static route.
- 8.8.8.8 is publicly addressed while 192.168.1.10 belongs to private RFC 1918 space.
Explanation
Correct Answer
A:Correct. This mechanism fits the observed network symptom at the fictional Oakside Warehouse: IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol. The corresponding remedy is “Check neighbor solicitation and advertisement traffic for the IPv6 peer on the local link.”. Confirmation: The neighbor cache shows the resolved link-layer address after ICMPv6 discovery.
Incorrect Answers
B:That cause belongs to a different case: Two laptops use 192.168.2.20/24 and 192.168.3.20/24; the technician treats them as directly on-link because both addresses begin 192.168. The observed fictional Oakside Warehouse condition is specifically explained by “IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol.”.
C:That cause belongs to a different case: A support analyst believes an internal 192.168.50.0/24 address can be made public solely by changing the router's default route. The observed fictional Oakside Warehouse condition is specifically explained by “IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol.”.
D:That cause belongs to a different case: A network drawing marks 8.8.8.8 and 192.168.1.10 as the same address-scope type for internet routing. The observed fictional Oakside Warehouse condition is specifically explained by “IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol.”.