CCNA IP Routing Practice Test 12 — 15 Questions

Question 1

A router has a default route and a specific route to 203.0.113.0/24. Which route is used for traffic to 203.0.113.25?

Accepted Answer

The specific route to 203.0.113.0/24. The specific route to 203.0.113.0/24 is used because it is a more specific match than the default route. In plain language, even though the default route could technically match almost anything, the router always prefers a route that more precisely describes the destination network. Since 203.0.113.25 is inside 203.0.113.0/24, that route wins under longest-prefix match.

This is one of the most basic routing-table interpretation rules. The default route remains important as a fallback, but it is not chosen when a more specific valid route exists.

Answer

The default route

Answer

Both routes are always load-balanced

Answer

Neither route because defaults cannot coexist with specific routes

Question 2

Two routers are directly connected and running OSPF. Their IP addresses and hello timers match, but they still do not become neighbors. One side is configured for area 0 and the other for area 1 on the shared link. What is the most likely cause?

Accepted Answer

The interfaces are in different OSPF areas on the shared link.. An OSPF area mismatch is the most likely cause. In plain language, the routers may be physically connected and able to exchange packets, but OSPF still requires that both sides agree on the area associated with the shared segment. If one interface belongs to area 0 and the other belongs to area 1, the routers do not view the segment in the same OSPF context and the adjacency fails.

This is a classic CCNA troubleshooting case because the addressing can look perfect while the protocol still refuses to form a neighbor relationship. OSPF is strict about several interface-level values, and the area assignment is one of the most important.

Answer

The routers need identical hostnames.

Answer

The link must be converted to a trunk.

Answer

The routers must use static routes first.

Question 3

A routing table contains these entries for the same destination space: 10.1.0.0/16, 10.1.10.0/24, and 0.0.0.0/0. Which route is used for traffic to 10.1.10.44?

Accepted Answer

10.1.10.0/24. The 10.1.10.0/24 route is used because it is the most specific matching prefix. In plain language, even though the /16 route and the default route could also match, the /24 route describes the destination range more precisely. Longest-prefix match therefore selects the /24 entry.

This is a foundational route-selection rule. The default route remains important as a fallback, but it is not used when more specific routes exist. Likewise, the /16 route is less specific than the /24, so it loses for this destination.

Answer

10.1.0.0/16

Answer

0.0.0.0/0

Answer

No route, because the entries overlap

Question 4

A router learns 172.16.0.0/16 from OSPF and 172.16.10.0/24 from a static route. Which route is used for traffic to 172.16.10.55?

Accepted Answer

The static /24 route. The static /24 route is used because it is more specific than the OSPF /16 route. In plain language, even though OSPF is a dynamic source and the /16 covers the destination broadly, the router prefers the entry that describes the exact destination range more precisely. Since 172.16.10.55 falls within 172.16.10.0/24, that route wins under longest-prefix match.

This is a classic example of route specificity taking priority before broader route-source comparisons would matter between equal prefix lengths.

Answer

The OSPF /16 route

Answer

The default route

Answer

Neither route because the prefixes overlap

Question 5

A router has routes to 192.168.0.0/16 and 192.168.100.0/24. Which route is used for traffic to 192.168.100.77?

Accepted Answer

192.168.100.0/24. The route to 192.168.100.0/24 is used because it is more specific. In plain language, even though the /16 route covers a large address range that includes the destination, the /24 route describes the destination network more precisely. Longest-prefix match therefore prefers the /24.

This is a basic but critical routing-table concept. The router does not choose the broader route when a narrower one matches the same destination.

Answer

192.168.0.0/16

Answer

Both routes are discarded because they overlap.

Answer

The default route is preferred if present.

Question 6

Why is a default route often called a route of last resort?

Accepted Answer

Because it is used only when no more specific route matches the destination.. Ly identifies the default route as a route of last resort because it is used only when no more specific route matches the destination. Option B is incorrect because bandwidth is not a defining characteristic of a default route; it is simply a fallback path. Option C is wrong because default routes can be configured statically or learned via any routing protocol (e.g., OSPF, EIGRP, RIP), not exclusively OSPF. Option D is false because the default route is the least specific route (0.0.0.0/0), not more specific than any other route.

Answer

Because it always has the lowest bandwidth.

Answer

Because it must be learned from OSPF only.

Answer

Because it is more specific than every other route.

Question 7

Which two statements accurately describe longest-prefix match?

Accepted Answer

The most specific matching route is preferred over broader matching routes.. Longest-prefix match means the router prefers the most specific route that matches the destination. In plain language, if several routes could all work, the router chooses the one that describes the destination range most precisely. That is why a /25 wins over a /24, and a /24 wins over a /16, when all of them match the same destination.

This is a foundational routing rule. The wrong answers usually confuse route specificity with route-source trust or assume the default route is considered first. The two correct answers are the ones that keep the focus on specificity.

Answer

The default route is always preferred over a matching specific route.

Answer

Administrative distance replaces the need for longest-prefix match.

Answer

A /16 is more specific than a /24.

Question 8

An engineer configures a floating static route to 0.0.0.0/0 with an administrative distance of 200 while OSPF is providing a default route. What is the intended behavior?

Accepted Answer

The static default route acts as a backup and becomes active only if the OSPF default route is lost.. The intended behavior is that the static default route stays in reserve and becomes active only if the OSPF-learned default route disappears. In plain language, the administrator wants a backup path, not a replacement for the normal OSPF path. By assigning the static route a higher administrative distance than OSPF, the router treats it as less trustworthy during normal operation.

This is a standard floating-static design. The static route is still configured, but it does not normally appear as the preferred forwarding choice until the lower-distance route is lost. That is the key operational purpose of the configuration.

Answer

The static default route overrides OSPF immediately because it is manually configured.

Answer

Both default routes must always load-balance together.

Answer

The router ignores both defaults because they overlap.

Question 9

A router has a connected route to 192.168.1.0/24 and also has a default route. Which route is used for traffic to 192.168.1.55?

Accepted Answer

The connected route to 192.168.1.0/24. The connected route is used because it is both directly attached and more specific than the default route. In plain language, the router already knows that the destination belongs to one of its local interface networks, so it has no reason to send that traffic to a fallback route.

This is one of the most basic route-selection behaviors. Default routes matter only when no better match exists. Here, a directly connected, exact matching network is already present.

Answer

The default route

Answer

Both routes equally

Answer

Neither route

Question 10

A network engineer configures OSPF between R1 and R2, but the routers never become neighbors on GigabitEthernet0/0. Based on the exhibit, what is the most likely cause?

Accepted Answer

The OSPF interface timers do not match.. The most likely cause is a hello/dead timer mismatch. In practical terms, both routers are on the same subnet and both are trying to run OSPF in area 0, so the obvious items look correct. But OSPF does not form adjacency based on IP reachability alone. It also checks whether key interface parameters agree. Hello and dead intervals are among those required parameters.

On R1, the hello interval is 10 seconds and the dead interval is 40 seconds. On R2, the hello interval is 5 seconds and the dead interval is 20 seconds. That mismatch is enough to prevent the neighbor relationship from forming. This is a common CCNA troubleshooting pattern because the interfaces can still ping each other, which makes the failure look less obvious at first glance.

Answer

The routers are using different OSPF areas.

Answer

The routers must use the same hostname to become neighbors.

Answer

The subnet mask prevents multicast OSPF traffic.

Question 11

A router has the following routes in its table: 172.16.0.0/16, 172.16.20.0/24, and 172.16.20.128/25. Which route is used for traffic to 172.16.20.200?

Accepted Answer

172.16.20.128/25. The /25 route is used because it is the most specific match. In plain language, the router looks for the narrowest route that still contains the destination address. Since 172.16.20.200 falls inside 172.16.20.128/25, that route wins over the broader /24 and /16 entries.

This is a direct longest-prefix-match question. It is meant to reinforce that specificity comes first in routing-table lookup. Broader routes remain useful, but they are not chosen when a more precise matching entry exists.

Answer

172.16.0.0/16

Answer

172.16.20.0/24

Answer

The default route

Question 12

R1 and R2 are directly connected. Both are configured in OSPF area 0, and they can successfully ping each other. However, OSPF neighbor adjacency fails. R1's interface is configured with `ip ospf authentication message-digest` and a valid key, while R2's interface has no OSPF authentication configured. What is the most likely cause?

Accepted Answer

The OSPF authentication settings do not match.. The most likely cause is an OSPF authentication mismatch. Although the routers have IP connectivity and are in the same OSPF area, OSPF adjacency requires matching security parameters. R1 uses message-digest authentication whereas R2 has none configured, preventing neighbor formation. The other options are incorrect: the stem confirms they are in the same area (A), OSPF does not require identical hostnames (C), and successful pings prove the subnet mask does not block multicast traffic (D).

Answer

The routers are in different OSPF areas.

Answer

The routers need identical hostnames before adjacency can form.

Answer

The subnet mask prevents OSPF multicast traffic.

Question 13

A router has a static route to 10.20.20.0/24 and also has a default route. Which route is used for traffic to 10.20.20.8?

Accepted Answer

The static route to 10.20.20.0/24. The static route to 10.20.20.0/24 is used because it is more specific than the default route. In practical terms, the router always chooses the route that most precisely matches the destination before falling back to the default route.

This question reinforces the idea that the default route is a route of last resort, not a preferred choice when a better match already exists.

Answer

The default route

Answer

Both routes are used equally

Answer

Neither route is valid

Question 14

Which two statements accurately describe passive interfaces in OSPF?

Accepted Answer

It suppresses OSPF hello packets on that interface.. A passive interface stops the router from sending OSPF hello packets on that interface, which means the router will not try to form neighbors there. In practical terms, this is useful on user-facing or stub-like links where no OSPF neighbor should exist. However, passive does not necessarily mean the connected network disappears from OSPF. The network can still be advertised through the router’s other active adjacencies.

This is a common design and security practice because it reduces unnecessary routing chatter on interfaces that should not form adjacencies in the first place.

Answer

It converts OSPF on that interface into static routing.

Answer

It forces the interface IP address to become the router ID.

Answer

It disables OSPF on every interface in the router automatically.

Question 15

A router learns 10.0.0.0/8 from OSPF and 10.10.0.0/16 from a static route. Which route is used for traffic to 10.10.20.1?

Accepted Answer

The static 10.10.0.0/16 route. The static /16 route is used because it is more specific than the OSPF /8 route. In practical terms, even though both routes match the destination, the router chooses the one that narrows the destination range more precisely. Since 10.10.20.1 belongs to 10.10.0.0/16, that entry wins.

This question reinforces that longest-prefix match comes first. The broader OSPF route still matters for other destinations inside 10.0.0.0/8, but not for this one.

Answer

The OSPF 10.0.0.0/8 route

Answer

The default route if present

Answer

Neither route, because the networks overlap