CCNA Practice Test 40 — 15 Questions

Question 1

Refer to the exhibit. A network administrator configures NAT overload on R1 to allow internal hosts in the 10.1.1.0/24 subnet to access the Internet. After the configuration, the administrator runs the show ip nat translations verbose command and notices that several internal sessions all appear to use the same inside global port 1024. The administrator is concerned that port conflicts will occur. Based on the output, which statement is correct?

Accepted Answer

The translations are extended entries, so the combination of inside global IP, outside global IP, and port ensures each session is unique, even though the inside global port is the same.. The exhibit shows four dynamic NAT translations, each marked with the 'extended' flag. In extended PAT, the translation table includes the destination IP address and port (the Outside global field). Even though all entries share the same inside global port 1024, each translation has a different Outside global pair (198.51.100.10:53 for UDP, 203.0.113.100:443 and 203.0.113.200:22 for TCP). Therefore, the five‑tuple (protocol, inside global IP, inside global port, outside global IP, outside global port) remains unique for each session, and no port conflict exists. The 'extended' flag explicitly confirms that the router is using this extended matching logic to allow port reuse.

Answer

The NAT configuration is missing the overload keyword, causing all internal hosts to share a single source port.

Answer

The static NAT entry mapping 203.0.113.5 to the entire 10.1.1.0/24 subnet forces all subordinate translations to use the same port 1024.

Answer

The dynamic NAT pool is exhausted, forcing the router to reuse port 1024 for all new sessions.

Question 2

Exhibit: R1 can ping 10.1.23.2 but cannot ping 192.168.3.10 behind R3. The routing table on R1 lacks 192.168.3.0/24. What is the best next check?

Accepted Answer

Verify whether the remote LAN is being advertised into the routing process. Because the directly connected next router is reachable, the problem is likely missing routing information for the remote LAN. The best next check is whether R3 is advertising 192.168.3.0/24 or whether that network is present in the routing domain at all.

Answer

Replace the Ethernet cable between R1 and R2

Answer

Change the OSPF router ID on R1 immediately

Answer

Disable CEF so the route can be learned

Question 3

Exhibit: An OSPFv2 adjacency between two routers on Ethernet is not forming. Which two mismatches would directly prevent the routers from becoming neighbors?

Accepted Answer

Different OSPF area assignments on the interfaces. On an OSPFv2 network, area mismatch and authentication mismatch both directly prevent adjacency formation. Mismatched timers (such as hello or dead intervals) also block adjacency on all network types, including Ethernet. In this scenario, the correct choices are area mismatch (A) and authentication mismatch (B).

Answer

Different hostnames on the routers

Answer

Different loopback addresses used for management

Answer

One router using SSH version 2

Question 4

Exhibit: A static route to 172.16.40.0/24 is configured, but traffic still follows the default route. Which two explanations are plausible?

Accepted Answer

The next hop for the static route may not be reachable. If a static route points to an unreachable next hop or the outgoing interface is down, the route may not be installed as usable. In that case the router can still use a less specific route such as the default route.

Answer

The default route always overrides more specific routes

Answer

Static routes require a metric lower than 1

Answer

The destination prefix must be configured under router ospf first

Question 5

A static default route is configured on R1 toward ISP-A, and a second default route toward ISP-B is configured with a higher administrative distance. Which two statements are correct during normal operation and after ISP-A failure?

Accepted Answer

The route through ISP-A is preferred during normal operation. This is a classic floating static design. The lower-AD default route is primary, and the higher-AD default waits in reserve.

Answer

Both defaults are always installed and used equally

Answer

The backup route is ignored permanently because only one default route can exist

Question 6

A branch router is running single-area OSPF. An engineer wants an interface to advertise its connected network into OSPF but must prevent hello packets from being sent on that LAN segment. Which two actions achieve that goal?

Accepted Answer

Enable OSPF on the interface or matching network statement. In OSPF, a passive interface still advertises the connected network but does not send or process hello packets. So the interface must participate in OSPF, and then it must be made passive.

Answer

Set the interface network type to point-to-point

Answer

Apply distribute-list out on the interface

Question 7

A route table shows both a default route and a more specific route to 192.168.50.0/24. Which two statements describe how packets destined for 192.168.50.25 are handled?

Accepted Answer

The router prefers the 192.168.50.0/24 route because it is the longest prefix match. Once routes are installed, packet forwarding follows longest prefix match. The /24 route is more specific than the default route, so traffic to 192.168.50.25 uses the /24 entry.

Answer

Administrative distance is compared before prefix length for forwarding decisions

Answer

The packet is load-balanced across both routes automatically

Question 8

A router shows the following routing table entries for the same destination:

O    10.10.50.0/24 [110/20] via 192.168.12.2, GigabitEthernet0/0
D    10.10.50.0/24 [90/30720] via 192.168.13.2, GigabitEthernet0/1

Which route will become the active route in the routing table?

Accepted Answer

The EIGRP route, because its administrative distance is lower. The EIGRP route becomes active because the router compares administrative distance first when the same destination is learned from different routing protocols. This is one of the most common Cisco exam traps: candidates compare the OSPF metric value of 20 to the EIGRP metric value and assume the smaller number must win. That is not how route selection works across different protocols. OSPF metrics and EIGRP metrics are calculated differently, so the router does not compare them directly. Instead it checks administrative distance. EIGRP internal routes default to 90, while OSPF routes default to 110. Since 90 is lower than 110, the EIGRP route is trusted more and is installed as the active path.

Answer

The OSPF route, because its metric is lower

Answer

Both routes, because the prefixes are identical

Answer

Neither route, because the metrics use different scales

Question 9

A router interface is configured for OSPF, but neighbors do not form. The engineer checks the interface and sees Hello 10 and Dead 40. The neighbor on the same segment uses Hello 30 and Dead 120.

What is the most likely cause of the OSPF adjacency failure?

Accepted Answer

OSPF timers do not match. The adjacency fails because the OSPF hello and dead timers do not match. OSPF neighbors on the same segment must agree on several key parameters before they accept each other as neighbors, and the timer settings are one of those required matches. In plain terms, each router is expecting to hear OSPF hellos at one rhythm, but the other side is speaking at a different rhythm, so the relationship never becomes valid. This is different from cost, which matters later during path selection after neighbors are already exchanging information. The timer mismatch is a classic CCNA troubleshooting point because the interfaces can be up and IP connectivity can even appear normal while the OSPF adjacency still fails.

Answer

Router IDs are identical

Answer

The interface cost is too low

Answer

The subnet mask is invalid because it is a transit link

Question 10

A routing table entry begins with the code C. What does that code indicate?

Accepted Answer

A connected network. In Cisco routing table output, C indicates a directly connected network. These routes are installed when an interface is up and has an address in that subnet.

Answer

A route learned through EIGRP

Answer

A candidate default route

Answer

A static route to a classful network

Question 11

Which OSPF network type on Ethernet performs a DR and BDR election by default?

Accepted Answer

Broadcast. Broadcast multiaccess networks such as Ethernet elect a DR and BDR by default.

Answer

Point-to-point

Answer

Point-to-multipoint nonbroadcast

Answer

Loopback

Question 12

Two OSPF routers connected on an Ethernet link remain in the INIT state. Which issue is the most likely cause?

Accepted Answer

The routers cannot exchange Hellos bidirectionally on the segment. INIT means a router is seeing Hellos from its neighbor but does not see its own router ID in the neighbor field of received Hellos. A common cause is one-way communication or a mismatched multicast/adjacency problem, often at Layer 2.

Answer

The routers have identical router IDs

Answer

The routers have already reached FULL and are waiting to install routes

Answer

The routers are using the same OSPF process ID

Question 13

Two OSPF routers connected over Ethernet fail to become neighbors. Their interfaces are up/up and in the same IPv4 subnet. One router uses area 0 and the other uses area 1 on the connecting interfaces. What is the most likely cause?

Accepted Answer

Mismatched OSPF areas on the shared link. OSPF neighbors on the same link must agree on key parameters, including the area assigned to that interface. A mismatch prevents the adjacency from forming.

Answer

Mismatched OSPF process IDs

Answer

Missing default routes

Answer

Different router IDs

Question 14

Which two statements accurately describe longest-prefix match in routing?

Accepted Answer

The most specific matching route is preferred over broader matching routes.. Longest-prefix match means a router prefers the most specific route that matches the destination. In plain language, if several entries could apply to a packet, the router chooses the one that narrows the destination range most precisely. This is why a /25 can beat a /24, and a /24 can beat a /16, even if all three technically contain the same destination address.

The common mistake is to assume the router always begins with protocol trust or metric. Those factors matter, but only after the router has determined which matching routes share the same prefix length.

Answer

A default route is preferred over a matching /24 because it is simpler.

Answer

Routers ignore subnet masks and choose only by administrative distance.

Answer

A /16 is always more specific than a /24.

Question 15

A route to 10.10.20.0/24 disappears when an OSPF adjacency fails. Which design would most directly provide an automatic backup without changing the primary OSPF path during normal operation?

Accepted Answer

A floating static route with a higher administrative distance than OSPF. The most direct design is a floating static route with a higher administrative distance than OSPF. In plain language, that means the router keeps a manually configured backup route in reserve but does not use it while the OSPF route remains healthy. If the OSPF path disappears, the backup static route becomes active automatically. This is a very common and practical way to add simple failover.

The key requirement in the question is that the primary OSPF path should remain unchanged under normal conditions. A normal static route with default distance would override OSPF and break that goal. A floating static route avoids that by staying less preferred until a failure occurs. That is why it is the correct design choice here.

Answer

A standard static route with the default administrative distance of 1

Answer

Removing OSPF entirely and using only a default route

Answer

Disabling the routing table on the router until failure occurs