Cisco Certified Network Associate (CCNA) 200-301 Practice Test 36
Question 350
An IPv6 router has an installed unicast route `2001:db8:100:50::/64` via the on-link next hop `fe80::2` on Gi0/1. `show ipv6 route` displays the correct prefix, but packets to 2001:db8:100:50::99 are dropped. The router has sent repeated Neighbor Solicitations for `fe80::2` and receives no Neighbor Advertisement. Which verification isolates the forwarding failure?
- Check `show ipv6 neighbors` for the Gi0/1 next-hop `fe80::2`, verify the neighbor/adjacency is unresolved, and restore on-link NDP reachability before expecting the installed route to forward packets.
- Prefer any less-specific installed /48 route automatically because an unresolved NDP entry changes the destination longest-prefix rule.
- Use an IPv4 ARP cache entry for 192.0.2.2 to complete the IPv6 `fe80::2` adjacency.
- Change the DNS A record of the destination to a different IPv4 address, without checking Neighbor Solicitations.
Explanation
Correct Answer
A:The route is present in the IPv6 routing table, but a Layer 3 next-hop on an Ethernet link still needs a link-layer neighbor mapping. IPv6 Neighbor Discovery sends solicitations to resolve and verify neighbors. With no advertisements, the forwarding adjacency stays incomplete; prefix selection alone is not sufficient for packet delivery.
Incorrect Answers
B:The routing lookup still selects the most specific matching installed route; a failed neighbor resolution affects adjacency/forwarding, not prefix ordering.
C:IPv6 uses ICMPv6 Neighbor Discovery rather than IPv4 ARP to map IPv6 next hops.
D:The observed traffic already uses an IPv6 literal and fails at the IPv6 next-hop adjacency.
Question 351
A network acceptance test follows this reported failure: The network uses an OSPF cost 70 path even though an equal-prefix cost 20 path is available and the technician is reading the wrong field. Which verification most specifically demonstrates the repaired function rather than checking an unrelated feature?
- Treat route age 00:00:01 as a cost of one and ignore the bracketed metric.
- The installed OSPF path for the exact prefix has metric cost 20 and chosen next hop, not cost 70, with equal route-source AD.
- Prefer the cost 70 route because a larger OSPF cost means higher throughput.
- Prefer an unrelated default route with lower AD over the matching OSPF /24.
Explanation
Correct Answer
B:When two candidates are equally preferred by source and prefix, OSPF shortest-path cost determines which is installed. Inspect `[110/metric]` and interfaces on the actual destination entry.
Incorrect Answers
A:The elapsed-time field is not the OSPF cost.
C:OSPF selects lower total cost; reference bandwidth settings may influence how costs are calculated.
D:Most-specific route matching precedes default fallback.
Question 352
A branch routing engineer is validating a repair. Earlier, traffic to an unallocated subnet inside the summary is sent to Null0, but live more-specific child prefixes still forward normally. Which postchange check most directly establishes the specific problem is resolved?
- All child destinations disappear into Null0 even though specific child routes are installed.
- A known child prefix inside the summary uses its installed longer specific route, while an unallocated hole in that summary correctly matches the aggregate Null0 discard.
- Traffic for an unallocated hole is routed through an arbitrary unrelated default next hop, despite a matching Null0 summary.
- The Null0 summary replaces every physical interface with no ingress L2 forwarding anywhere.
Explanation
Correct Answer
B:Null0 summary routes can prevent loops by swallowing only traffic that lacks a more-specific child. The validation should exercise one real child destination and one reserved hole.
Incorrect Answers
A:Longest-prefix match forwards reachable child networks ahead of the broad discard summary.
C:The more-specific aggregate Null0 route wins over the default for that address.
D:A Null0 route applies to destinations matching that prefix, not globally to all IP forwarding.
Question 353
An edge router reaches upstream gateway 198.51.100.1 through an operational routed interface. Internal routes are present, but destinations with no specific match have no path. Which Cisco IOS IPv4 configuration adds the normal fallback?
- ip default-gateway 0.0.0.0 255.255.255.0
- router ospf 1 followed only by network 0.0.0.0 255.255.255.255 area 0
- ipv6 route ::/0 198.51.100.1
- ip route 0.0.0.0 0.0.0.0 198.51.100.1
Explanation
Correct Answer
D:The normal IPv4 default prefix is 0.0.0.0/0, represented in Cisco IOS static route syntax with destination 0.0.0.0 and mask 0.0.0.0. Point it to the reachable upstream next hop, 198.51.100.1: ip route 0.0.0.0 0.0.0.0 198.51.100.1. The router then forwards IPv4 traffic lacking a more-specific match toward that gateway, subject to ARP and interface reachability. Verify show ip route lists S* 0.0.0.0/0 and that a real upstream path is functional. The default route is a last-resort entry: existing more-specific connected, static, or learned routes continue to take precedence when a destination matches them.
Incorrect Answers
A:The ip default-gateway command applies mainly to a device not performing IP routing, such as management forwarding on a Layer 2 switch. It is not the ordinary route-table default for an IP-routing router. Its arguments also do not resemble a valid specific next-hop gateway configuration. A routing-enabled edge router should use ip route for the static default.
B:OSPF network statements select interfaces for protocol participation in a process and area; they do not simply create an IPv4 gateway of last resort. A router that needs a specific static fallback can install the default route directly. OSPF default propagation would be a separate routing design and require appropriate configuration and upstream reachability.
C:The ipv6 route command installs an IPv6 routing entry and ::/0 is the IPv6 default prefix. It cannot use an IPv4 next-hop string as an ordinary IPv6 route destination. The problem explicitly concerns IPv4 reachability to otherwise unmatched IPv4 destinations; it needs an IPv4 default entry in the routing table.
Question 354
An IPv6-enabled branch router has a directly reachable provider next hop 2001:db8:0:1::1 on Gi0/0. The design requires a catch-all path for IPv6 destinations that lack more-specific routes. Which IOS configuration supplies that default route?
- `ip route 0.0.0.0 0.0.0.0 2001:db8:0:1::1` mixing IPv4 route syntax with IPv6 next hop.
- `ipv6 route 2001:db8:0:1::/64 ::/0` with the connected provider network as destination.
- `ipv6 route ::/0 2001:db8:0:1::1` on the IPv6 routing device, with the next hop reachable through Gi0/0.
- `ipv6 route fe80::/10 2001:db8:0:1::1` limited to link-local destinations instead of a default.
Explanation
Correct Answer
C:An IPv6 default route is written as prefix ::/0 because zero leading destination bits match any IPv6 address when no more-specific entry applies. With a reachable global-unicast next hop, `ipv6 route ::/0 2001:db8:0:1::1` provides that fallback path; the router recursively resolves the next hop through its connected provider interface. Check that IPv6 routing and interface addresses are correctly configured, then inspect `show ipv6 route` and test a remote destination. This route does not replace required more-specific routes, and the provider must have a valid return path for successful end-to-end connectivity.
Incorrect Answers
A:The `ip route` command and 0.0.0.0/0 prefix describe IPv4 routes. Appending an IPv6 address as the next hop mixes address families and is not the requested IOS IPv6 configuration. For IPv6 the command prefix is `ipv6 route` and the default destination is written ::/0.
B:The prefix 2001:db8:0:1::/64 names the connected provider network, not the set of all otherwise-unmatched IPv6 destinations. The ::/0 notation in the next-hop position also does not identify a reachable peer address. The default requires ::/0 as destination and a valid next hop.
D:The prefix fe80::/10 covers IPv6 link-local addressing rather than arbitrary remote global-unicast destinations. Installing a route only for fe80 addresses does not provide a catch-all path to the Internet or another IPv6 site. Use the default prefix ::/0 for unmatched destinations.
Question 355
A proposed network design has this requirement: A static route should cover remote 10.50.20.0/24 through 192.0.2.2 without unintentionally covering nearby prefixes. Which choice is technically appropriate for that deployment?
- Use `ip route 10.50.0.0 255.255.0.0 192.0.2.2` for only 10.50.20.0/24.
- Use `ip route 10.50.20.0 255.255.255.128 192.0.2.2` expecting all of the /24 to match.
- Install only `ip route 0.0.0.0 0.0.0.0 192.0.2.2` and claim it cannot affect any adjacent prefix.
- Configure `ip route 10.50.20.0 255.255.255.0 192.0.2.2` and ensure 192.0.2.2 is an eligible next hop.
Explanation
Correct Answer
D:The /24 mask 255.255.255.0 restricts the route to 10.50.20.0–255, not adjacent 10.50.21.0/24. An IOS static route needs a valid next-hop resolution to appear as an active forwarding route.
Incorrect Answers
A:A /16 would also select numerous neighboring 10.50.x networks.
B:A /25 only covers the lower half of the required subnet.
C:A default route is overbroad, matching all otherwise-unmatched destinations rather than only the specified /24.
Question 356
A branch routing engineer must implement a change. A router needs a static destination for exactly 198.51.100.42/32 rather than an entire /24 remote subnet. Which technical decision most directly meets these requirements?
- Use `ip route 198.51.100.42 255.255.255.255 <reachable-next-hop>` for the single IPv4 host.
- Use `ip route 198.51.100.0 255.255.255.0 <next-hop>` and call it host-specific.
- Use `ip route 198.51.100.0 255.255.255.128 <next-hop>` assuming .42 is the only address matched.
- Use only an IPv4 default route and expect other destinations to remain unaffected.
Explanation
Correct Answer
A:A /32 mask matches exactly 198.51.100.42. It will not change how packets to .43 or the rest of the /24 are routed.
Incorrect Answers
B:A /24 covers 256 addresses, not one /32 host.
C:A /25 includes addresses .0–.127, much broader than one host.
D:0/0 matches many unrelated remote destinations without a more specific route.
Question 357
A service IPv6 2001:db8:abcd::42 should receive its own /128 route without redirecting the rest of that /64. The team needs a solution consistent with this requirement. Which option is the most appropriate design or configuration decision?
- Configure `ipv6 route 2001:db8:abcd::/64 ...` when only ::42 should use that path.
- Use `ipv6 route 2001:db8:abcd::42/128 <next-hop-or-interface-as-appropriate>` with a resolvable IPv6 next hop.
- Configure `ipv6 route ::/0 ...` because it affects only the service host.
- Use an IPv4 /32 mask of 255.255.255.255 as the IPv6 prefix for 2001:db8:abcd::42.
Explanation
Correct Answer
B:An IPv6 /128 specifies one exact unicast destination, whereas /64 selects an entire subnet. If the next hop is a link-local address, IOS also requires the outgoing interface.
Incorrect Answers
A:A /64 would redirect all addresses in the broader service subnet.
C:The IPv6 default is least specific and can carry many other destinations.
D:IPv6 static destinations use colon-hex address and prefix length /128, not dotted decimal IPv4 netmasks.
Question 358
A branch routing engineer is evaluating a deployment. A static failover next hop must have greater AD than the dynamic primary route so it installs only after primary loss. What approach correctly addresses the stated requirement?
- Leave static AD at 1 and expect it to remain dormant behind the OSPF 110 path.
- Configure a static /32 while OSPF advertises /24 and expect a high AD to keep the /32 dormant for that host.
- Configure a static backup to the identical destination prefix with AD higher than the primary OSPF AD 110, such as `ip route 10.50.20.0 255.255.255.0 192.0.2.6 200`.
- Use an unreachable backup next hop and assume AD 200 guarantees failover.
Explanation
Correct Answer
C:A floating static route waits behind the preferred dynamic route as long as that primary is eligible. When OSPF withdraws, the static can install if its own next hop is reachable.
Incorrect Answers
A:Lower AD 1 makes the static the preferred source to the same network.
B:The more-specific /32 affects its host independently of the broad /24 prefix and can still win longest match.
D:A floating route still needs a valid forwarding adjacency once primary disappears.
Question 359
A proposed network design has this requirement: A static IPv4 route refers to a directly reachable next hop on a multiaccess Ethernet link, allowing normal ARP adjacency. Which choice is technically appropriate for that deployment?
- Specify only the Ethernet exit interface for a distant /24 and assume ARP never occurs for destination hosts.
- Use a next-hop address from an unrelated unconnected subnet without any recursive route and expect it to resolve automatically.
- Specify an on-link next-hop IP such as `ip route 10.50.20.0 255.255.255.0 192.0.2.2` and resolve that neighbor by ARP on Ethernet.
- Set the Ethernet interface to shutdown and assume the static can still forward.
Explanation
Correct Answer
C:On a multiaccess Ethernet segment, naming the reachable next hop normally directs ARP to that neighbor rather than ARPing separately for every remote destination through an interface-only static.
Incorrect Answers
A:An interface-only Ethernet static can cause ARP for each destination and dependence on proxy ARP.
B:The next hop must resolve through a usable route to an adjacent egress neighbor.
D:An unavailable egress interface provides no working L2 adjacency.
Question 360
A branch routing engineer must implement a change. A point-to-point serial link has a single peer, allowing an exit-interface static route without broadcast-layer next-hop ambiguity. Which technical decision most directly meets these requirements?
- Use an interface-only static to a large remote network over broadcast Ethernet and assume it cannot create proxy-ARP overhead.
- Use an exit-interface static route such as `ip route 203.0.113.0 255.255.255.0 Serial0/0/0` on the true point-to-point serial link.
- Configure `ip route 203.0.113.0 0.0.0.0 Serial0/0/0` and interpret 0.0.0.0 as a /24 mask.
- Use a down serial interface as the only egress and expect the destination static to remain usable.
Explanation
Correct Answer
B:A genuine point-to-point link has only one downstream peer, so an interface-only route can identify the correct next hop without multiaccess Ethernet ARP ambiguity.
Incorrect Answers
A:Multiaccess Ethernet may need a specified next-hop to avoid ARP for many remote destinations.
C:A zero mask is a default prefix, not /24.
D:The route depends on an operational point-to-point link.