Cisco Certified Support Technician (CCST) Networking 100-150 Practice Test 22
Question 210
An incident reviewer analyzes this observation: At the fictional Lakebridge Travel Office during a scheduled lab validation, the team observes: A branch device has 172.20.14.8 but a technician labels it public because every 172.x.x.x address is public. What is the MOST specific underlying cause?
- The RFC 1918 private range spans 172.16.0.0 through 172.31.255.255, including 172.20.14.8.
- IPv6 does not use IPv4-style broadcast; multicast serves applicable group communication roles.
- IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol.
- For 192.168.40.0/24, .0 is the network ID, .255 is the directed broadcast, and .1 is a valid host.
Explanation
Correct Answer
A:Correct. This mechanism fits the observed network symptom at the fictional Lakebridge Travel Office: The RFC 1918 private range spans 172.16.0.0 through 172.31.255.255, including 172.20.14.8. The corresponding remedy is “Apply the correct 172.16.0.0/12 private address boundary to the branch inventory.”. Confirmation: The classification distinguishes private 172.20.14.8 from an address such as 172.40.14.8.
Incorrect Answers
B:That cause belongs to a different case: A technician expects IPv6 to send a subnet-wide broadcast address like 192.168.1.255 when contacting all local nodes. The observed fictional Lakebridge Travel Office condition is specifically explained by “The RFC 1918 private range spans 172.16.0.0 through 172.31.255.255, including 172.20.14.8.”.
C:That cause belongs to a different case: An engineer expects an IPv6 host to ARP for a neighbor's MAC address exactly as IPv4 does. The observed fictional Lakebridge Travel Office condition is specifically explained by “The RFC 1918 private range spans 172.16.0.0 through 172.31.255.255, including 172.20.14.8.”.
D: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 Lakebridge Travel Office condition is specifically explained by “The RFC 1918 private range spans 172.16.0.0 through 172.31.255.255, including 172.20.14.8.”.
Question 211
After an approved correction, the support team reviews: At the fictional Lakebridge Travel Office during a scheduled lab validation, the team observes: A branch device has 172.20.14.8 but a technician labels it public because every 172.x.x.x address is public. The approved corrective action is: “Apply the correct 172.16.0.0/12 private address boundary to the branch inventory.” Which result BEST demonstrates success?
- ARP and neighbor checks identify only one MAC for each intended IP after remediation.
- The endpoint can ARP for the gateway and reach an off-subnet test host.
- The expanded address contains exactly eight 16-bit groups and round-trips to the short form.
- The classification distinguishes private 172.20.14.8 from an address such as 172.40.14.8.
Explanation
Correct Answer
D:Correct. This is the required observable acceptance evidence for “Apply the correct 172.16.0.0/12 private address boundary to the branch inventory.” at the fictional Lakebridge Travel Office. It demonstrates correction of the original cause: The RFC 1918 private range spans 172.16.0.0 through 172.31.255.255, including 172.20.14.8.
Incorrect Answers
A:That result is evidence for a separate corrective action, “Assign separate available host addresses and confirm unique ARP mappings.”. It does not establish the intended outcome “The classification distinguishes private 172.20.14.8 from an address such as 172.40.14.8.” for the fictional Lakebridge Travel Office case.
B: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 classification distinguishes private 172.20.14.8 from an address such as 172.40.14.8.” for the fictional Lakebridge Travel Office case.
C:That result is evidence for a separate corrective action, “Expand 2001:db8::5 into eight hextets with the correct number of zero groups.”. It does not establish the intended outcome “The classification distinguishes private 172.20.14.8 from an address such as 172.40.14.8.” for the fictional Lakebridge Travel Office case.
Question 212
Before approving the action, review: At the fictional Lakebridge Travel Office during a scheduled lab validation, the team observes: A branch device has 172.20.14.8 but a technician labels it public because every 172.x.x.x address is public. During “Apply the correct 172.16.0.0/12 private address boundary to the branch inventory.”, which precaution MOST specifically prevents a related risk?
- Do not use a /24 mask with a documented /27 prefix length.
- Do not treat 2001:db8:: documentation space as a routable production IPv6 allocation.
- Do not label every 172/8 address private or every 172/8 address public.
- Do not assume unique-local IPv6 prefixes are globally routed by internet providers.
Explanation
Correct Answer
C:Correct. This precaution prevents a second fault while applying “Apply the correct 172.16.0.0/12 private address boundary to the branch inventory.” at the fictional Lakebridge Travel Office. The required protection is “Do not label every 172/8 address private or every 172/8 address public.”; success still requires “The classification distinguishes private 172.20.14.8 from an address such as 172.40.14.8.”.
Incorrect Answers
A: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 label every 172/8 address private or every 172/8 address public.”.
B:This caution is appropriate for a separate failure pattern: An IPv6 endpoint is configured with 2001:db8:abcd:2::9/64 for a lab and the technician expects it to be a publicly assigned production Internet prefix. The principal adjacent risk here is controlled by “Do not label every 172/8 address private or every 172/8 address public.”.
D:This caution is appropriate for a separate failure pattern: A student sees fd34:5:6::10 and labels it a global publicly reachable address merely because it is 128 bits long. The principal adjacent risk here is controlled by “Do not label every 172/8 address private or every 172/8 address public.”.
Question 213
A technician reviews the following issue: At the fictional Cedar Valley Academy during basic configuration verification, the team observes: A receptionist reports 169.254.88.2 on a Windows laptop and the team tries to treat it as an ordinary assigned internet WAN address. Which action MOST directly resolves the reported issue?
- Assign separate available host addresses and confirm unique ARP mappings.
- Investigate the DHCP or static configuration path before relying on the link-local address for routed access.
- Expand 2001:db8::5 into eight hextets with the correct number of zero groups.
- Assign the printer one of 10.8.12.73 through 10.8.12.78 instead.
Explanation
Correct Answer
B:Correct. In the fictional Cedar Valley Academy case, An IPv4 169.254.0.0/16 link-local address often indicates automatic self-assignment when normal address configuration is unavailable. The specified corrective action, “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.”, directly targets that condition. Evidence of resolution: The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.
Incorrect Answers
A: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 Cedar Valley Academy finding instead needs “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.”, verified by “The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.”.
C:That action addresses a different network issue: A student expands 2001:db8::5 into an address with two separate :: compression markers and too many hextets. The present fictional Cedar Valley Academy finding instead needs “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.”, verified by “The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.”.
D:That action addresses a different network issue: A technician is given 10.8.12.72/29 and assigns .79 to a printer, assuming every number in the block is usable. The present fictional Cedar Valley Academy finding instead needs “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.”, verified by “The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.”.
Question 214
An incident reviewer analyzes this observation: At the fictional Cedar Valley Academy during basic configuration verification, the team observes: A receptionist reports 169.254.88.2 on a Windows laptop and the team tries to treat it as an ordinary assigned internet WAN address. What is the MOST specific underlying cause?
- An IPv4 169.254.0.0/16 link-local address often indicates automatic self-assignment when normal address configuration is unavailable.
- Duplicate IPv4 host addresses on the same broadcast segment can cause ARP conflicts and loss of stable delivery.
- 2001:db8::/32 is reserved for documentation examples rather than publicly routed production allocation.
- 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 Cedar Valley Academy: An IPv4 169.254.0.0/16 link-local address often indicates automatic self-assignment when normal address configuration is unavailable. The corresponding remedy is “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.”. Confirmation: The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.
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 Cedar Valley Academy condition is specifically explained by “An IPv4 169.254.0.0/16 link-local address often indicates automatic self-assignment when normal address configuration is unavailable.”.
C:That cause belongs to a different case: An IPv6 endpoint is configured with 2001:db8:abcd:2::9/64 for a lab and the technician expects it to be a publicly assigned production Internet prefix. The observed fictional Cedar Valley Academy condition is specifically explained by “An IPv4 169.254.0.0/16 link-local address often indicates automatic self-assignment when normal address configuration is unavailable.”.
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 Cedar Valley Academy condition is specifically explained by “An IPv4 169.254.0.0/16 link-local address often indicates automatic self-assignment when normal address configuration is unavailable.”.
Question 215
After an approved correction, the support team reviews: At the fictional Cedar Valley Academy during basic configuration verification, the team observes: A receptionist reports 169.254.88.2 on a Windows laptop and the team tries to treat it as an ordinary assigned internet WAN address. The approved corrective action is: “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.” Which result BEST demonstrates success?
- The capture shows IPv6 multicast delivery instead of a directed or limited broadcast packet.
- The link's address plan lists two valid interface hosts between its network and broadcast addresses.
- The IPv6 forwarding table lists ::/0 and can select it for destinations without a more-specific route.
- The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.
Explanation
Correct Answer
D:Correct. This is the required observable acceptance evidence for “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.” at the fictional Cedar Valley Academy. It demonstrates correction of the original cause: An IPv4 169.254.0.0/16 link-local address often indicates automatic self-assignment when normal address configuration is unavailable.
Incorrect Answers
A:That result is evidence for a separate corrective action, “Identify the appropriate link-local IPv6 multicast group for the intended discovery or group message.”. It does not establish the intended outcome “The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.” for the fictional Cedar Valley Academy case.
B:That result is evidence for a separate corrective action, “Design an appropriate /30 segment when exactly two traditional IPv4 host addresses are needed.”. It does not establish the intended outcome “The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.” for the fictional Cedar Valley Academy case.
C:That result is evidence for a separate corrective action, “Use ::/0 with the appropriate IPv6 next hop in the IPv6 routing table.”. It does not establish the intended outcome “The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.” for the fictional Cedar Valley Academy case.
Question 216
Before approving the action, review: At the fictional Cedar Valley Academy during basic configuration verification, the team observes: A receptionist reports 169.254.88.2 on a Windows laptop and the team tries to treat it as an ordinary assigned internet WAN address. During “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.”, which precaution MOST specifically prevents a related risk?
- 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 assume an IPv4 link-local address is normally routed by the site's default gateway.
- Do not use a /24 mask with a documented /27 prefix length.
Explanation
Correct Answer
C:Correct. This precaution prevents a second fault while applying “Investigate the DHCP or static configuration path before relying on the link-local address for routed access.” at the fictional Cedar Valley Academy. The required protection is “Do not assume an IPv4 link-local address is normally routed by the site's default gateway.”; success still requires “The laptop later receives its intended LAN address and default gateway instead of only a 169.254.x.x value.”.
Incorrect Answers
A: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 assume an IPv4 link-local address is normally routed by the site's default gateway.”.
B:This caution is appropriate for a separate failure pattern: An IPv6 client has ::1 and the engineer tries to use it as the next-hop router address. The principal adjacent risk here is controlled by “Do not assume an IPv4 link-local address is normally routed by the site's default gateway.”.
D: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 assume an IPv4 link-local address is normally routed by the site's default gateway.”.
Question 217
A technician reviews the following issue: At the fictional Pinefield Logistics while assessing a controlled network fault, the team observes: A developer uses 127.0.0.1 as the server address in an application deployed to other PCs on the LAN. Which action MOST directly resolves the reported issue?
- Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.
- Replace client-side loopback targeting with the server's reachable interface name or address.
- Check neighbor solicitation and advertisement traffic for the IPv6 peer on the local link.
- Identify .1 as a valid default gateway host and .255 as the broadcast for the subnet.
Explanation
Correct Answer
B:Correct. In the fictional Pinefield Logistics case, IPv4 127.0.0.0/8 is loopback to the local host, not a remote server reachable from peers. The specified corrective action, “Replace client-side loopback targeting with the server's reachable interface name or address.”, directly targets that condition. Evidence of resolution: Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.
Incorrect Answers
A:That action addresses a different network issue: An IPv6 client has ::1 and the engineer tries to use it as the next-hop router address. The present fictional Pinefield Logistics finding instead needs “Replace client-side loopback targeting with the server's reachable interface name or address.”, verified by “Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.”.
C:That action addresses a different network issue: An engineer expects an IPv6 host to ARP for a neighbor's MAC address exactly as IPv4 does. The present fictional Pinefield Logistics finding instead needs “Replace client-side loopback targeting with the server's reachable interface name or address.”, verified by “Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.”.
D:That action addresses a different network issue: A LAN router's 192.168.40.1/24 interface is documented as the segment broadcast destination rather than a valid host. The present fictional Pinefield Logistics finding instead needs “Replace client-side loopback targeting with the server's reachable interface name or address.”, verified by “Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.”.
Question 218
An incident reviewer analyzes this observation: At the fictional Pinefield Logistics while assessing a controlled network fault, the team observes: A developer uses 127.0.0.1 as the server address in an application deployed to other PCs on the LAN. What is the MOST specific underlying cause?
- IPv4 127.0.0.0/8 is loopback to the local host, not a remote server reachable from peers.
- A /27 contains only 32 total IPv4 addresses and 30 conventional usable hosts; /26 provides 62 usable.
- In a /26, .18 is in 192.168.60.0–.63 while .126 is in a different subnet .64–.127.
- IPv6 uses Neighbor Discovery with ICMPv6 rather than the IPv4 ARP protocol.
Explanation
Correct Answer
A:Correct. This mechanism fits the observed network symptom at the fictional Pinefield Logistics: IPv4 127.0.0.0/8 is loopback to the local host, not a remote server reachable from peers. The corresponding remedy is “Replace client-side loopback targeting with the server's reachable interface name or address.”. Confirmation: Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.
Incorrect Answers
B: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 Pinefield Logistics condition is specifically explained by “IPv4 127.0.0.0/8 is loopback to the local host, not a remote server reachable from peers.”.
C: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 Pinefield Logistics condition is specifically explained by “IPv4 127.0.0.0/8 is loopback to the local host, not a remote server reachable from peers.”.
D:That cause belongs to a different case: An engineer expects an IPv6 host to ARP for a neighbor's MAC address exactly as IPv4 does. The observed fictional Pinefield Logistics condition is specifically explained by “IPv4 127.0.0.0/8 is loopback to the local host, not a remote server reachable from peers.”.
Question 219
After an approved correction, the support team reviews: At the fictional Pinefield Logistics while assessing a controlled network fault, the team observes: A developer uses 127.0.0.1 as the server address in an application deployed to other PCs on the LAN. The approved corrective action is: “Replace client-side loopback targeting with the server's reachable interface name or address.” Which result BEST demonstrates success?
- The client reaches its router using a nonloopback interface address and ::1 still tests itself.
- The capture shows IPv6 multicast delivery instead of a directed or limited broadcast packet.
- The endpoint can ARP for the gateway and reach an off-subnet test host.
- Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.
Explanation
Correct Answer
D:Correct. This is the required observable acceptance evidence for “Replace client-side loopback targeting with the server's reachable interface name or address.” at the fictional Pinefield Logistics. It demonstrates correction of the original cause: IPv4 127.0.0.0/8 is loopback to the local host, not a remote server reachable from peers.
Incorrect Answers
A:That result is evidence for a separate corrective action, “Configure a reachable next-hop address and keep ::1 for local IPv6 loopback tests.”. It does not establish the intended outcome “Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.” for the fictional Pinefield Logistics case.
B:That result is evidence for a separate corrective action, “Identify the appropriate link-local IPv6 multicast group for the intended discovery or group message.”. It does not establish the intended outcome “Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.” for the fictional Pinefield Logistics case.
C: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 “Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.” for the fictional Pinefield Logistics case.
Question 220
Before approving the action, review: At the fictional Pinefield Logistics while assessing a controlled network fault, the team observes: A developer uses 127.0.0.1 as the server address in an application deployed to other PCs on the LAN. During “Replace client-side loopback targeting with the server's reachable interface name or address.”, which precaution MOST specifically prevents a related risk?
- Do not place an IPv4 default prefix in an IPv6-only routing table.
- Do not confuse the first usable host with the subnet's broadcast address.
- Do not give LAN clients 127.0.0.1 as the address of a separate host.
- 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 “Replace client-side loopback targeting with the server's reachable interface name or address.” at the fictional Pinefield Logistics. The required protection is “Do not give LAN clients 127.0.0.1 as the address of a separate host.”; success still requires “Clients reach the actual server while 127.0.0.1 continues to reference each client's own machine.”.
Incorrect Answers
A:This caution is appropriate for a separate failure pattern: A router carries an IPv6 default route and a trainee writes it as 0.0.0.0/0 in the IPv6 route table. The principal adjacent risk here is controlled by “Do not give LAN clients 127.0.0.1 as the address of a separate host.”.
B:This caution is appropriate for a separate failure pattern: A LAN router's 192.168.40.1/24 interface is documented as the segment broadcast destination rather than a valid host. The principal adjacent risk here is controlled by “Do not give LAN clients 127.0.0.1 as the address of a separate host.”.
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 give LAN clients 127.0.0.1 as the address of a separate host.”.