Cisco Certified Network Associate (CCNA) 200-301 Practice Test 39
Question 380
A router has been configured with ipv6 route ::/0 2001:db8:1::1 toward a reachable upstream router. Which output specifically establishes that the IPv6 default static route is installed?
- show ipv6 route static displays S ::/0 via 2001:db8:1::1
- show ip route static displays an IPv4 S* 0.0.0.0/0 entry
- show ipv6 neighbors lists the link-layer address of an upstream node
- show ipv6 interface brief displays a global-unicast interface address
Explanation
Correct Answer
A:The IPv6 route table stores installed IPv6 prefix routes separately from IPv4. A static ::/0 route shown by show ipv6 route static with next hop 2001:db8:1::1 demonstrates the exact configured fallback prefix has been selected and can participate in IPv6 forwarding. The next hop must also remain reachable for packets to be delivered. If an application still fails, test a destination without a more-specific route and inspect neighbor resolution and the interface path, but do not confuse an up interface or a learned neighbor with proof that the actual default route exists in the routing table.
Incorrect Answers
B:The IPv4 routing table uses 0.0.0.0/0, not ::/0. Even a valid IPv4 static default route cannot provide forwarding for an otherwise unmatched IPv6 destination. Cisco platforms maintain protocol-specific routes, so the corresponding show ip route output does not answer whether the requested IPv6 route was installed. The required evidence must come from show ipv6 route or its static-route view.
C:An IPv6 neighbor entry demonstrates that a router has resolved a neighbor at the link layer. It cannot by itself prove which destination prefixes will use that neighbor or whether the default static entry was accepted into the IPv6 route table. Neighbor discovery may work for an on-link router while all external IPv6 packets still lack a route. Verify the installed ::/0 route separately.
D:A globally addressed and operational IPv6 interface proves the local interface has usable address state. A router may have such an address and still lack a default path for remote prefixes. An address on the upstream-facing link is a prerequisite, not proof of the exact installed ::/0 prefix. A route-table check is necessary to establish the fallback forwarding decision.
Question 381
An IPv4 static route to 10.50.20.0 was corrected from a /25 to a /24. Earlier, 10.50.20.40 was reachable but 10.50.20.200 was not covered by that route. Which acceptance check most directly demonstrates the corrected prefix and next-hop now cover both destinations?
- Confirm only that a default IPv4 S* route exists, without inspecting 10.50.20.0.
- Inspect the installed 10.50.20.0/24 next-hop route and verify forwarding or probes for both 10.50.20.40 and 10.50.20.200.
- Look up a separate 198.51.100.42/32 route to one remote host.
- Inspect the installed IPv6 ::/0 static route even though the incident uses IPv4.
Explanation
Correct Answer
B:The /24 mask covers .0–.255, including both test addresses, while the old /25 covered only .0–.127. Verifying the installed next hop plus both probes demonstrates that the intended static prefix and forwarding path work for the full LAN.
Incorrect Answers
A:A default route may carry unmatched traffic without correcting the intended static /24. The requirement is to verify exact destination-prefix coverage of both halves of 10.50.20.0/24.
C:A /32 route to a different host covers only one address and says nothing about the corrected 10.50.20.0/24 network.
D:IPv6 route state is separate from IPv4. Seeing ::/0 installed cannot prove the IPv4 static route has the right mask and next hop.
Question 382
R1 has a static IPv4 host route `ip route 198.51.100.42 255.255.255.255 192.0.2.2`. A teammate incorrectly says it will also route traffic to 198.51.100.43. Which forwarding-table verification most directly proves the true scope of this /32 route?
- Check only that `show ip route static` lists an unrelated default route with an S* code.
- Look up both `198.51.100.42` and `198.51.100.43`: the /32 entry matches .42 via 192.0.2.2 but cannot match .43.
- Look up an IPv6 `/128` route for an unrelated IPv6 destination and infer the IPv4 match.
- Confirm that any route to `198.51.100.0/24` exists, without checking which prefix forwards .42 or .43.
Explanation
Correct Answer
B:An IPv4 `/32` matches one exact 32-bit address: 198.51.100.42. A separate lookup for .43 cannot select that entry, although another broader or default route may still forward .43. This paired destination lookup distinguishes route scope from general reachability.
Incorrect Answers
A:A default route can send packets with no more-specific match, but it cannot prove that a particular /32 static entry covers a second host. The question concerns IPv4 longest-prefix matching for two neighboring addresses.
C:IPv6 routes occupy a separate routing table and use 128-bit addresses. Their prefix lengths do not validate the match performed by the IPv4 forwarding lookup for the named hosts.
D:A `/24` is broader than a `/32`; its existence neither proves that .42 uses the intended host route nor that .43 matches that host route. Inspect the specific best-match result for each destination.
Question 383
A router has `ipv6 route 2001:db8:feed::25/128 2001:db8:1::1`. A reviewer must confirm that this is a host-specific static route, not an accidentally broader /64 that could steer traffic for other hosts. Which command evidence best verifies the exact installed destination prefix?
- `show ipv6 route 2001:db8:feed::25/128` reports a static /128 entry toward the expected next hop.
- A successful ping to 2001:db8:feed::25, without displaying the installed prefix or forwarding path.
- `show ipv6 route static` lists at least one static entry, but the reviewer does not inspect its destination prefix length.
- `show ipv6 neighbors` resolves 2001:db8:1::1 to a link-layer neighbor without showing the remote destination route.
Explanation
Correct Answer
A:The route lookup must include the exact host destination and a 128-bit prefix. Seeing an installed static entry for `2001:db8:feed::25/128` and the correct next hop proves that the route is host-specific rather than a broader network route. Cisco's IPv6 routing table differentiates destination prefix lengths and next-hop forwarding information. Checking exact route selection also helps ensure a more-specific unintended entry has not replaced it. A ping is useful supplemental reachability evidence but cannot by itself demonstrate the configured prefix length.
Incorrect Answers
B:Ping to a single IPv6 address tests whether that address can be reached and answered at the time of the test. It does not reveal whether the router forwarded using a /128 host route, a /64 network route, a default route, or a different more-specific path. Because the review specifically concerns unintended route scope, reachability alone could pass while the original defect remains. Inspect the IPv6 routing table for the exact destination and prefix, then use reachability testing as a secondary confirmation.
C:`show ipv6 route static` is an appropriate broad inventory command, but merely seeing some static-route output does not demonstrate that the desired `/128` entry is installed or that its prefix has not been mistyped. The technician needs to inspect the actual destination, prefix length, and next-hop information for the particular service address. A list of unrelated static routes would be an especially weak acceptance signal. The more focused route lookup explicitly ties the result to the one address and host-mask requirement.
D:An IPv6 neighbor entry connects an on-link IPv6 next-hop address to its link-layer address. That can help confirm Layer 2 reachability to `2001:db8:1::1`, but it does not tell the reviewer whether remote `2001:db8:feed::25` is matched by a `/128` route or a larger prefix. The next hop may resolve correctly for a mistaken broad network route as well. Route-table destination and prefix evidence must precede neighbor information when validating the scope of the forwarding entry.
Question 384
A branch routing engineer is validating a repair. Earlier, a supposed backup route has AD 1, which outranks the existing OSPF AD 110 path and becomes primary unexpectedly. Which postchange check most directly establishes the specific problem is resolved?
- During normal operation the static AD 1 remains installed ahead of OSPF, with no failover test.
- The static AD is 200 but its backup next hop cannot resolve after OSPF withdrawal.
- With OSPF primary active, the RIB selects OSPF AD 110 while the corrected static backup has a higher configured AD; after controlled OSPF loss, the static installs.
- Only a router hostname change is confirmed while the active route remains S at AD 1.
Explanation
Correct Answer
C:The former static had AD 1 and stole traffic. Two-phase testing confirms normal preference and backup operability, not just that the static has a larger number in configuration.
Incorrect Answers
A:A default-distance static route with AD 1 can win over the equal-prefix OSPF route with AD 110 even when it was intended only as backup. The repair must raise the static administrative distance above the primary and confirm OSPF remains installed until primary withdrawal.
B:Correct preference alone does not prove recovery traffic will forward.
D:Hostname does not address route administrative distance.
Question 385
The earlier fault was recorded as follows: R1 tries to ARP for a next hop outside all connected subnets because no valid route resolves the configured next-hop IP. After corrective work, which observation provides direct evidence that the affected function now behaves correctly?
- The next-hop address remains off-link with no route, but the static command exists in running-config.
- `show ip route <next-hop>` and adjacency checks show a valid egress path to the corrected on-link next hop; the installed static route and end-to-end destination test succeed.
- An ARP entry exists for a different VLAN neighbor while the configured next hop remains unreachable.
- A DNS query resolves the remote hostname while the RIB has no installed static path.
Explanation
Correct Answer
B:The original next hop was off-link and unresolved. Confirm an actual routing/ARP adjacency before inferring that the static destination is usable.
Incorrect Answers
A:Static intent without usable recursion cannot forward packets.
C:Unrelated adjacency cache entries do not prove this gateway can be reached.
D:DNS resolution is independent of IP forwarding to the selected network.
Question 386
A branch routing engineer has repaired a network problem. An engineer copied interface-only syntax to Ethernet, causing repeated ARP attempts for diverse destination IPs through proxy ARP. Which device or protocol check is the strongest evidence that this particular failure is gone?
- The static still specifies only the Ethernet interface and keeps ARPing for every remote destination through proxy ARP.
- The Ethernet interface is up but the configured static gateway remains undefined and remote traffic fails.
- An OSPF router ID has been assigned though the interface-only static is unchanged.
- The repaired Ethernet static explicitly names a directly reachable next hop; `show arp` resolves that gateway rather than creating per-destination proxy ARP entries, and forwarding succeeds.
Explanation
Correct Answer
D:A specific neighbor gateway avoids ambiguity of interface-only multiaccess statics. Verify route next hop and ARP behavior under multiple remote destinations rather than simply observing carrier.
Incorrect Answers
A:An interface-only IPv4 static route on multiaccess Ethernet can trigger ARP/proxy-ARP resolution for numerous remote destination IPs. Leaving that configuration intact does not prove next-hop-specific forwarding has replaced the unwanted behavior.
B:Physical link alone does not establish a usable L3 next hop.
C:OSPF router identity cannot repair how the static route uses Ethernet ARP.
Question 387
A network acceptance test follows this reported failure: Recursive lookup sends the next hop toward an unintended interface after a topology change because the static route was not fully specified. Which verification most specifically demonstrates the repaired function rather than checking an unrelated feature?
- The static keeps only an unresolved or recursively redirected next hop and still exits the unintended interface.
- The correct next-hop IP appears in configuration but the active RIB resolves it toward another physical link.
- The static entry shows the intended specified outgoing interface and adjacent next hop, and traffic to its destination exits that interface after the topology change.
- Only a VLAN name is corrected while no route/forwarding path is tested.
Explanation
Correct Answer
C:A fully specified static can pin both route destination and egress characteristics. Confirm actual forwarding path with RIB/FIB lookup and controlled neighbor/link changes.
Incorrect Answers
A:An unqualified static next hop can recursively resolve through an unintended connected interface. If the observed outgoing interface remains wrong, the route has not been fully constrained using the appropriate next-hop plus egress interface.
B:A configured address alone does not prove egress is constrained as intended.
D:Layer 2 naming cannot validate the specific route recursion and interface-selection repair.
Question 388
A branch routing engineer is validating a repair. Earlier, the configured IPv6 default has only fe80::2 and no egress interface; IOS cannot select the correct link for that scoped address. Which postchange check most directly establishes the specific problem is resolved?
- Configure only `ipv6 route ::/0 fe80::2` and assume IOS can infer the unique physical link from this link-local address alone.
- Use IPv4 `ip route 0.0.0.0 0.0.0.0 ...` as the sole IPv6 default.
- Confirm another IPv6 LAN’s /64 connected route but leave default ::/0 absent.
- `show ipv6 route ::/0` now includes the correct outgoing interface with `fe80::2` as its link-local next hop, and IPv6 neighbor resolution plus a remote test succeed.
Explanation
Correct Answer
D:IPv6 link-local addresses have interface scope; the same fe80::2 can occur on multiple links. A static default using a link-local next hop must specify the outgoing interface to disambiguate the neighbor.
Incorrect Answers
A:A link-local address is not globally unique and requires exit interface context for a static next hop.
B:IPv4 and IPv6 have separate route tables and command syntax.
C:A local /64 cannot reach arbitrary unmatched IPv6 destinations.
Question 389
R1 has an intentional static summary route `ip route 10.50.16.0 255.255.240.0 Null0`, with separate more-specific routes for the live VLAN subnets. After removing one obsolete subnet, the network team must confirm that traffic for unused addresses within the summary is discarded instead of looping to a default route. Which evidence meets that requirement?
- `show ipv6 route static` contains an unrelated IPv6 default route.
- `show ip route` displays the provider-facing default route but does not inspect the 10.50.16.0/20 summary.
- `show ip arp` resolves the next-hop MAC of a live subnet without testing unused summary addresses.
- `show ip route 10.50.23.10` selects the 10.50.16.0/20 Null0 summary and a controlled probe to that unused destination is discarded rather than sent upstream.
Explanation
Correct Answer
D:The route lookup for unused 10.50.23.10 falls inside 10.50.16.0/20 but outside any remaining live child route by the scenario's condition. The installed summary therefore points to Null0 and drops the packet, preventing accidental upstream routing loops. A controlled probe plus route or CEF inspection shows that forwarding outcome, while a separate lookup to each live subnet should select its more-specific operational path. This verifies the discard-summary design rather than just the existence of some static route or unrelated interface counter.
Incorrect Answers
A:An IPv6 routing table reports paths for a different address family, whereas the configured discard summary is an IPv4 route to Null0. Even a healthy IPv6 default route says nothing about longest-prefix selection for addresses inside 10.50.16.0/20. The acceptance criterion is to ensure an unused IPv4 address in the summary is handled locally, not forwarded by a broader default toward the provider. Query the specific IPv4 destination and validate the observed discard behavior.
B:The default route is relevant only for IPv4 destinations with no more-specific installed match. The intentionally installed /20 Null0 summary is more specific than 0.0.0.0/0 for destinations inside 10.50.16.0 through 10.50.31.255. Merely displaying the provider default cannot prove that this summary exists or will be preferred. Inspect a destination within the abandoned portion of the summary and verify that the selected route is the discard entry, while live more-specific subnet routes remain preferred.
C:An ARP table entry proves a device can resolve a neighbor on an Ethernet segment, but it does not reveal which route a remote, unused destination matches. If the Null0 summary were missing, an ARP entry could still be healthy while the packet follows a default route upstream and potentially loops. The test must target the summary's forwarding decision. A next-hop MAC lookup for a live subnet is a different check and does not establish safe discard behavior for abandoned address space.
Question 390
A router is about to join OSPF process 10. The engineer wants its OSPF router ID to remain `10.255.255.1` even if interface addresses later change. Which IOS configuration directly establishes that stable identity before OSPF starts?
- Set `ip ospf authentication` on an uplink without choosing a router ID.
- Set `ip ospf priority 0` on the transit interface to prevent DR election.
- Enter `router ospf 10` and configure `router-id 10.255.255.1`.
- Configure `passive-interface` on each neighbor-facing OSPF uplink.
Explanation
Correct Answer
C:`router-id` under the OSPF routing process sets the 32-bit identifier directly, independent of physical interface renumbering. On an already active process, a router-ID change may require an OSPF process restart to take effect; setting it before startup avoids this issue.
Incorrect Answers
A:OSPF authentication protects adjacency formation when matching settings and credentials exist; it does not explicitly select a 32-bit OSPF router ID for the process.
B:Interface priority affects DR/BDR eligibility on broadcast or NBMA networks, not the OSPF router identifier advertised by the router. A priority-zero router still has an OSPF router ID.
D:Passive interfaces suppress OSPF Hellos and adjacency formation on selected interfaces. They do not select the router ID, and marking actual transit links passive would prevent neighbor relationships.
