CCNA IPV6 Questions

The subnet mask /24 is too large, causing a mismatch with R2's /30; the default gateway must be R2's IP (203.0.113.2); EUI-64 is not used on G0/0.

The duplicate IPv4 address on G0/1 is not resolved; it still uses 192.168.1.1 which is already assigned to R3.

EUI-64 is required on G0/0, not G0/1; static IPv6 is required on G0/1, not G0/0.

OSPFv2 supports only IPv4; OSPFv3 is required for IPv6 routing.

OSPFv3 uses a 32-bit router-id, which must be manually configured or derived from an IPv4 address; without it, the process cannot operate.

Verification commands like 'show ospfv3 neighbor' and 'show ipv6 route ospf' are necessary to ensure OSPFv3 is functioning correctly.

Link-local addresses are not routable; they are confined to a single link or network segment. Routers will not forward packets with a link-local source or destination address beyond the local subnet.

While EUI-64 is one method for generating the interface ID, link-local addresses can also use randomly generated identifiers (privacy extensions) or be manually configured. The statement that they always use EUI-64 is incorrect.

The default gateway for IPv6 hosts is typically a global unicast or unique local address, not a link-local address. While routers may send Router Advertisements with a link-local source, the default gateway address learned by hosts is the router's link-local address, but the host uses that link-local address as the next-hop, not as the default gateway address itself. The statement is misleading because the default gateway is often the link-local address of the router, but the host uses it as the next-hop, not as a routable address.

The specific factual error: Using a /24 mask on a point-to-point link wastes addresses and may cause subnet overlap; also, R2 needs a default route to reach R1's IPv4 address if the mask is /30, but with /24 they are in the same subnet so no default route is needed, but the mask is still wrong.

The specific factual error: R2's IPv4 mask must match R1's mask to ensure both routers agree on the subnet boundary. Using /28 on R2 while R1 uses /30 creates a mismatch.

The specific factual error: Assigning the same IPv6 address to both routers causes a duplicate address conflict, preventing communication.

The question states the serial link is up/up on both sides, meaning the interface is not administratively down. An administratively down interface would show as 'administratively down' in the interface status, not 'up/up'.

Both interfaces have IPv6 addresses in the 2001:DB8:1:1::/64 subnet, so the subnet matches. OSPFv3 does not require interfaces to be in the same subnet for adjacency, but it does require link-local addresses to be reachable. However, the given addresses are global unicast, and the subnet match is not the issue here.

The router-id is configured on R2 as 2.2.2.2, as stated in the existing explanation. OSPFv3 requires a router-id, and it is present, so this is not the cause.

This option is incorrect because the command shown is a static route configuration, not a command to enable OSPFv3 on an interface. OSPFv3 requires separate routing protocol configuration commands.

This option is incorrect because the prefix specified is a specific network (2001:db8:100::/64), not the default IPv6 route (::/0). Therefore, it does not create a default route.

This option is incorrect because static route commands do not convert interfaces into tunnels. Tunnel interfaces require explicit tunnel configuration commands, which are not present here.

This option is incorrect because it uses the IPv4 static route syntax (ip route) with an IPv6 next-hop address, which is invalid and will not configure a proper IPv6 route.

This command creates a specific static route to the 2001:db8:ff::/64 prefix with a next hop of ::1, which is not a default route and does not forward all unknown IPv6 traffic.

The ipv6 default-gateway command is not used for static routing configuration and does not install a default route in the routing table, making it ineffective for forwarding unknown IPv6 destinations.

The floating route must have a higher AD than the primary route to act as a backup; setting it to 1 would make it preferred over the primary default route, violating the requirement.

AD 255 is reserved for routes that are not to be installed; a floating route needs an AD higher than the primary but less than 255 to be usable as backup.

The floating route is required by the scenario; removing it would eliminate the backup path, which is not the intended fix.

Loopback0 is not enabled for OSPF, so its prefix is not advertised into OSPF.

The 'network' command is invalid in OSPFv3 for IPv6; only interface-level 'ipv6 ospf ... area' commands are used.

Applying 'passive-interface GigabitEthernet0/0' prevents OSPF from forming a neighbor adjacency on the link, breaking the verification of neighbor state.

The specific factual error is that the EUI-64 keyword cannot be used with the double colon (::) abbreviation; the prefix must be fully specified.

The specific factual error is that the command does not use the eui-64 keyword, so it does not meet the requirement to use EUI-64.

The specific factual error is that the 7th bit inversion was not applied; the interface ID should start with 021C, not 001C.

The IPv6 static route should use a fully specified next-hop (IPv6 address) rather than just an exit interface to avoid recursive routing failures.

Floating static routes require a higher administrative distance (e.g., 200) so they are only used when the primary route is unavailable.

A fully specified IPv6 static route includes both the exit interface and the next-hop IPv6 address to ensure proper routing.

The IPv6 subnet mismatch prevents direct connectivity; R1 and R3 must be on the same subnet for a ping to work without additional routing.

The requirement explicitly states that the IPv6 address must be derived using EUI-64; a manually specified interface ID violates this.

The IPv6 subnet must be the same as R3's for direct connectivity; using a different subnet requires additional routing, which is not configured.

Option B is incorrect because the static route command does not enable OSPFv3. OSPFv3 requires separate configuration commands and is a dynamic routing protocol, unlike static routes.

Option C is incorrect because routing does not convert link-local addresses into global unicast addresses. Address types remain consistent, and routing forwards packets based on existing address formats.

Option D is incorrect because ::/0 is a default route covering all IPv6 addresses, not a summary route with a /64 prefix. Summarization involves aggregating multiple routes into a larger prefix, which is not the case here.

Neighbor Solicitation (NS) messages are used for address resolution (determining the link-layer address of a neighbor) and duplicate address detection, not for advertising default gateway or prefix information.

DHCPv6 Solicit messages are used in stateful DHCPv6 to request configuration parameters like addresses and DNS servers, but SLAAC does not use DHCPv6 for default gateway or prefix information; those are provided by RA messages.

ICMP Echo Reply messages are used for ping responses and do not carry any routing or prefix information; they are not involved in neighbor discovery or address autoconfiguration.

The subnet mask on R1 G0/0 should be /30 to match R2, not /24.

The default gateway must be the neighbor's IP address, and IPv6 subnets must match for direct communication.

The requirement states EUI-64 on R1 G0/1, so static is not allowed.

The specific factual error is that OSPFv3 uses interface-level configuration, not network statements like OSPFv2 for IPv4.

The specific factual error is that OSPFv3 must be enabled on all interfaces that should participate in the routing process, including loopback interfaces.

The specific factual error is that OSPF router-ids must be unique. Using the same router-id on both routers prevents proper neighbor formation.

Invalid syntax: the eui-64 keyword cannot be used with a full 128-bit address; it requires only a prefix.

Missing the eui-64 keyword, so the interface would be configured with a static address rather than deriving the interface ID from the MAC.

Invalid syntax: the eui-64 keyword does not accept an explicit MAC address as an argument.

The specific factual error is that IPv6 unicast-routing is disabled by default on Cisco routers.

The specific factual error is that the command without 'eui-64' assigns a static address, not an EUI-64 address.

The specific factual error is assuming the EUI-64 address ends with ::1, which is not guaranteed.

A default static route is used as a gateway of last resort for any destination not in the routing table, regardless of whether dynamic routing protocols are configured. It is not dependent on the absence of dynamic routing.

A floating static route is designed to be a backup; therefore, it must have a higher AD than the primary route so that the primary route is preferred.

IPv6 static routes require an IPv6 next-hop address. Using an IPv4 address would be invalid because the router would not be able to resolve it in the IPv6 routing table.

The U/L bit was not flipped; the interface ID starts with 0011 instead of 0211.

The FFFE insertion is missing; the interface ID is just the MAC address written in IPv6 format.

FFFE is missing; only the U/L bit flip was applied.

This option focuses on a filtering issue, not the disabled routing engine, and would not cause the router’s own interface to lack a global unicast address.

NAT64 configuration would affect translation, but the root cause visible in the output is the lack of IPv6 routing capability on the router.

This shifts the blame to the host, but the router-side evidence (missing command and missing global unicast) clearly indicates a router configuration problem.

Uses 'ip route', which is for IPv4; IPv6 routes require 'ipv6 route'.

'ipv6 default-route' is not a valid Cisco IOS command.

'ip default-gateway' configures the management default gateway for IPv4, not an IPv6 routing entry.

Link-local addresses have a scope of link-local (fe80::/10) and are not forwarded by routers, making them non-routable across the Internet. They are intended only for communication on a single network segment.

Link-local addresses are automatically generated on all IPv6 interfaces regardless of DHCPv6. They are a mandatory part of IPv6 operation, not a fallback mechanism.

For off-link communication, IPv6 hosts still require a default gateway (usually a router's link-local address) to forward packets beyond the local segment. Link-local addresses do not eliminate the need for routing logic.

'ipv6 enable' is an interface command, not a global command to enable IPv6 routing.

'ip routing ipv6' is not a valid Cisco IOS command.

'ipv6 route enable' is not a valid Cisco IOS command.

OSPFv3 adjacency formation does not depend on hostnames; hostnames are only used for identification in show commands and have no impact on routing protocol operation.

OSPFv3 can use any valid IPv6 prefix length, including /64, /126, or /127, for the link between routers. The /64 requirement is for SLAAC, not for routing protocols.

OSPFv3 is specifically designed to run on directly connected interfaces, just like OSPFv2. It forms adjacencies over directly connected links to exchange routing information.

Adding a static route to the backup link does not correct the invalid next-hop 10.0.0.3 used in the default route and fails to address the root cause of the recursive lookup failure.

Swapping the administrative distances makes the backup path preferred instead of the primary, violating the requirement that R2 be the primary with AD 1.

Configuring the default route with an exit interface rather than a next-hop IP can cause ARP resolution issues in broadcast networks and does not replace the incorrect next-hop 10.0.0.3.

The specific factual error is that OSPFv3 uses interface-level commands ('ipv6 ospf area') rather than the network statement used in OSPFv2.

The specific factual error is that OSPFv3 interface configuration is required on each interface, not just globally.

The specific factual error is that 'router ospf' is for IPv4 OSPF; OSPFv3 requires 'ipv6 router ospf'.

OSPFv3 uses link-local addresses, not global unicast addresses, for neighbor formation.

OSPFv3 requires explicit interface configuration under the routing process; it is not automatically enabled.

The neighbor ID shown is the Router ID, not the IPv6 address of the neighbor's interface.

The next-hop is R1's own address (loop) and AD 1 makes the route equally preferred to dynamic routes, defeating the floating purpose.

AD 1 makes the route equally preferred, not a floating backup.

Adding a global 'router ospfv3 1' command is unnecessary; OSPFv3 can be enabled directly on the interface without a separate global configuration.

Using 'show ip ospf neighbor' and 'show ip route ospf' are IPv4 OSPFv2 commands, not valid for OSPFv3 which requires 'show ospfv3 neighbor' and 'show ipv6 route ospf'.

The 'show ipv6 route' command displays all IPv6 routes, not just OSPF-learned ones; the filter 'ospf' is required to see OSPF routes specifically.

Global unicast addresses are routable beyond the local link and are not automatically created for local link communication only.

Unique local addresses are similar to private IPv4 addresses and are routable within an organization, not limited to the local link.

Multicast addresses are used for group communication and are not assigned as interface addresses for unicast communication.

The 'show ipv6 interface' output shows 'up, line protocol is up', indicating the interface is not administratively down. An administratively down interface would show 'administratively down' in the output.

The link-local address (FE80::21A:2BFF:FE3C:4D5E) is correctly formed using EUI-64, which requires a valid MAC address. The presence of 'FF:FE' in the middle indicates EUI-64 is functioning properly, so the MAC address is valid.

The output shows 'ND router advertisements are sent every 200 seconds', confirming that Router Advertisements are enabled. The problem is about the router's own IPv6 address, not host autoconfiguration.

The specific factual error is that /24 masks are too large for point-to-point links and do not match the expected subnets for R2 and MLS1.

The specific factual error is that the IPv6 address should be configured with the EUI-64 keyword, not a static address.

The specific factual error is that the prefix length must be /64 as specified in the question; a /32 prefix is incorrect for this scenario.

'ipv6 router ospf <process-id>' is a global configuration command, not an interface command; enabling OSPFv3 on an interface requires the 'ipv6 ospf <process-id> area <area-id>' command.

'show ipv6 ospf neighbor' displays OSPFv3 neighbor adjacencies, not the link-state database; to view the LSDB, use 'show ipv6 ospf database'.

An A record maps a hostname to an IPv4 address, not an IPv6 address. Since the question specifically asks about IPv6, this record type is incorrect.

A CNAME record creates an alias from one domain name to another, not a direct mapping to an IP address. It does not provide the IP address itself, so it cannot verify the mapping to an IPv6 address.

MX records specify mail exchange servers for a domain and are used for email routing, not for mapping domain names to IP addresses. They do not provide IPv6 address mappings.

NAT rules are not required for native IPv6 communication and would not be the first suspect when a host cannot reach remote IPv6 destinations.

A VLAN trunk on the host NIC relates to Layer 2 segmentation, not to providing a default route for off-link IPv6 traffic.

A second global unicast address on the same interface does not supply the missing default route needed to reach off-link destinations.

The subnet mask is used to determine the network portion of an IP address and the host portion, not the DNS server address. DNS server addresses are configured separately, either manually or via DHCP.

IPv6 hosts can obtain their IP address via Stateless Address Autoconfiguration (SLAAC), which does not require DHCPv6. DHCPv6 is optional and used for stateful configuration or to provide additional parameters.

The default gateway must be on the same subnet as the host's IP address; otherwise, the host cannot send Ethernet frames to it because the gateway's MAC address would not be reachable via ARP. An arbitrary IP address would not work.

An IPv6 default gateway must be on the same local link, not just any globally routable address.

The subnet mask identifies the network bits, not the host bits; the host portion is the inverse of the mask.

DNS resolves names to IPs; hosts on the same subnet can communicate with IP addressing alone, making DNS optional.

The command lacks the 'eui-64' keyword, so it does not generate the interface ID from the MAC address.

The 'link-local' keyword is used for link-local addresses (fe80::/10), not for global prefixes.

The command does not assign the specified subnet prefix; it only activates IPv6 processing.

Manually configuring a link-local address with the eui-64 keyword is invalid; link-local addresses are automatically generated.

This option does not include the required ipv6 enable command, so it does not satisfy the explicit scenario requirement.

Uses a static host address (::1/64) instead of the eui-64 keyword, so the interface ID will not be generated from the MAC address.

The specific factual error: 192.0.2.2 is already used by R2, causing an IP conflict; static assignment on G0/1 does not guarantee uniqueness.

The specific factual error: /24 mask is too large and does not match the /30 subnet; EUI-64 cannot be applied alongside a static address—it replaces the interface ID.

The specific factual error: 192.0.2.2 is already assigned to R2, so R1 cannot use it; the correct fix is to adjust the mask, not the IP.

Administrative distance of 1 matches the default AD of a static route, so the floating route would not be less preferred; it needs a higher AD (e.g., 200) to act as a backup.

Using R1's own interface IPv6 address as next-hop would create a route pointing to itself, not to R2, and would not reach the loopback network.

The default route should use the default administrative distance (1) to remain the primary route; setting it to 200 would make it equal to the floating static route, causing unpredictable behavior.

The specific factual error is that the U/L bit was not flipped. The EUI-64 process requires flipping the seventh bit of the first byte of the MAC address.

The specific factual error is that FF:FE was not inserted between the first and second halves of the MAC address. The EUI-64 format requires the insertion of FF:FE.

The specific factual error is that the question asks for the resulting IPv6 address, not the configuration command. The command 'ipv6 address ... eui-64' is used to enable EUI-64, but the answer should be the actual address.

0.0.0.0/0 is the IPv4 default route; the correct IPv6 default prefix is ::/0.

A floating static route must have a higher AD, not lower, so that it is less preferred and only installed when the primary (lower AD) route is lost.

Cisco IOS requires the next-hop to be reachable, but it does not have to be directly connected. As long as a route exists to reach that next-hop (even recursively), the static route can be installed.

The 'network' command is for OSPFv2 and does not exist in OSPFv3; interface configuration is done via interface commands.

Setting the network type to point-to-point changes the OSPF link type; without matching configuration on R2, adjacency will fail.

Mismatched hello intervals prevent OSPF neighbor relationships from forming.

DHCPv6 is not a protocol that replaces ARP; instead, it is used for assigning IP addresses and configuration information to IPv6 devices. ARP is replaced by the Neighbor Discovery Protocol in IPv6, which performs similar functions for address resolution.

EUI-64 is not a protocol but a method for generating IPv6 interface identifiers. It does not perform the function of resolving link-layer addresses like ARP does in IPv4.

SLAAC (Stateless Address Autoconfiguration) is a method for automatically configuring IPv6 addresses but does not perform the function of resolving link-layer addresses like ARP does in IPv4. Therefore, it cannot replace ARP in IPv6.

IPv6 unicast-routing is already enabled; the problem is at the interface level.

The requirement specifies EUI-64; omitting it results in a static address that does not match the intended configuration.

The VLAN configuration is correct; no change is needed.

The statement incorrectly claims that link-local addresses are always assigned using EUI-64.

The statement confuses the role of EUI-64; it creates the interface ID, not the network prefix.

The statement is too restrictive; multiple default gateways can be configured, especially in multi-homed hosts.

The number range 100–199 is used for extended ACLs, not standard ones.

The placement advice is reversed: standard ACLs belong near the destination, not the source.

This is a common misconception; the ability to delete individual ACEs is a feature of named ACLs, not numbered.

A floating static route with a higher AD is installed when the lower AD route is removed because of interface failure.

Floating static routes do not distinguish between physical and administrative interface down events; the primary route is removed in both cases.

The immediate cause is the missing exit interface; neighbor discovery configuration does not make an incomplete static route valid.

The IPv6 next-hop 2001:db8:0:1::2 is not reachable via a directly connected network; the router cannot resolve it.

The administrative distance must be set to a higher value (e.g., 200) to make it a floating route.

The IPv6 route fails due to recursive lookup failure; adding AD does not fix the next-hop issue.

This option is incorrect because IPv6 gateways do not have to be global unicast; link-local addresses are valid for routing within the local network segment. The host can use the link-local address of the router as the next hop for packets destined to other networks.

This option is incorrect because a host with a link-local next hop can still reach global unicast addresses, as link-local addresses are used only for communication within the same local network segment.

This option is wrong because a router advertisement does not need to provide a MAC address for the next-hop link-local address to be valid; link-local addresses are inherently usable for local communication without MAC address specification.

The default gateway must be the IP address of the directly connected neighbor (R2's G0/0), which is 10.0.0.2, not 10.0.0.1.

The IP address 10.0.0.6/30 is in the same subnet as R2's G0/1 (10.0.0.5/30), so it does not resolve the duplicate address conflict. A different subnet must be used.

The specific factual error is that OSPFv3 uses interface-level configuration, not network statements under the OSPF process.

The specific factual error is that setting a router ID alone does not activate OSPFv3 on an interface; OSPFv3 must be explicitly enabled on the interface.

The specific factual error is that 'passive-interface default' would actually prevent adjacency, not help form it.

Creates a static route for a directly connected network that is already in the routing table, which is unnecessary.

On Ethernet interfaces, a static route must specify a next-hop IP address; specifying only an exit interface does not work for multi-access networks.

Creates a host route for the next-hop address itself, which is directly connected and already reachable, and does not provide a default route.

Incorrect. OSPFv3 forms adjacencies using IPv6 link-local addresses, so global unicast addresses are not mandatory for adjacency formation or neighbor discovery.

Incorrect. Router IDs must be unique identifiers for OSPF routers. Identical router IDs cause adjacency failure, but they do not need to be identical to form adjacency.

Incorrect. IPv6 link-local addresses are automatically configured on interfaces and do not require DHCPv6. OSPFv3 uses these link-local addresses for neighbor communication.

OSPFv3 requires the link interface to be enabled to form neighbors; loopback-only configuration results in no neighbor relationship.

OSPFv3 must be enabled on the loopback interfaces to advertise their prefixes; otherwise, they remain unknown to the neighbor.

Both routers must have OSPFv3 enabled on the link interface to form an adjacency, and both loopbacks must be enabled to advertise their prefixes.