CCNA IP Routing Practice Test 13 — 15 Questions

Question 1

R1 and R2 are directly connected and running OSPF. The IP addressing is correct and both routers are in area 0, but they do not form an adjacency. What is the most likely cause?

Accepted Answer

The OSPF MTU values do not match on the connected interfaces.. The most likely cause is an MTU mismatch between the two interfaces. During the OSPF database exchange process, neighbors must agree on the MTU value to successfully exchange DBD packets; a mismatch typically causes the adjacency to become stuck in the ExStart or Exchange state. Basic connectivity (e.g., ping) often still works because ICMP packets are small, but the OSPF adjacency fails due to the MTU discrepancy.

Answer

The routers must use identical hostnames before OSPF can form neighbors.

Answer

The routers must use VLAN 1 for OSPF to operate.

Answer

The interfaces need to be configured as trunks instead of routed ports.

Question 2

A router has routes to 192.168.100.0/24 and 192.168.100.128/25. Which route is used for traffic to 192.168.100.140?

Accepted Answer

192.168.100.128/25. The /25 route is used because it is the most specific matching prefix. In practical terms, 192.168.100.140 falls inside the upper half of the /24, which is exactly what the 192.168.100.128/25 route describes. Even though the /24 also matches, the router always prefers the narrower route when both are valid.

This is a direct longest-prefix-match question. It reinforces that specificity is checked before broader route-source preferences matter.

Answer

192.168.100.0/24

Answer

The default route

Answer

Neither route, because the prefixes overlap

Question 3

Match each route source or route type to its most accurate description.

Accepted Answer

Connected route: A route automatically added when an interface is configured with an IP address and is up.. Connected routes are automatically installed when an interface is configured with an IP address and is in the up/up state. Static routes are manually configured by an administrator to specify a fixed path. OSPF is a link-state routing protocol that uses cost as its metric and maintains a complete topology database. EIGRP is a hybrid protocol that uses bandwidth and delay as metrics and supports unequal-cost load balancing.

Question 4

R1 and R2 are directly connected and running OSPF. They can ping each other, the area matches, and the timers match, but they still do not become neighbors. What is the most likely cause?

Accepted Answer

The OSPF authentication keys do not match.. The most likely cause is a mismatch in OSPF authentication keys. Even though the routers have IP connectivity, matching area IDs, and identical timers, OSPF adjacency requires that authentication parameters also match. If authentication is enabled on both sides but the keys differ, OSPF packets are silently rejected, preventing neighbor formation.

Answer

The subnet mask is too small for OSPF to operate.

Answer

The routers must use different process IDs.

Answer

The interfaces must be configured as switch trunks.

Question 5

A router has routes to 172.20.0.0/16, 172.20.10.0/24, and 172.20.10.64/26. Which route is used for traffic to 172.20.10.70?

Accepted Answer

172.20.10.64/26. The /26 route is used because it is the most specific matching prefix. In practical terms, 172.20.10.70 falls inside the 172.20.10.64/26 range, so that route narrows the destination more precisely than the broader /24 and /16 routes. Longest-prefix match therefore selects the /26 entry.

This question is designed to reinforce that specificity comes first in route lookup. Broader routes remain useful, but they lose when a more exact route matches.

Answer

172.20.0.0/16

Answer

172.20.10.0/24

Answer

The default route

Question 6

A router has a directly connected route to 10.1.1.0/24 and a static default route. Which route is used for traffic to 10.1.1.200?

Accepted Answer

The directly connected 10.1.1.0/24 route. The directly connected route is used because it is the most specific and most immediate match. In practical terms, the router already knows that 10.1.1.200 belongs to a network on one of its own interfaces, so there is no reason to use the default route. The default route exists only for destinations that do not match anything more specific.

This is one of the most fundamental route-selection behaviors in IP routing.

Answer

The static default route

Answer

Both routes equally

Answer

Neither route

Question 7

A router has routes to 10.50.0.0/16, 10.50.10.0/24, and 10.50.10.128/25. Which route is used for traffic to 10.50.10.140?

Accepted Answer

10.50.10.128/25. The /25 route is used because it is the most specific matching prefix. In practical terms, 10.50.10.140 belongs to the upper half of the 10.50.10.0/24 space, which is exactly what 10.50.10.128/25 describes. Even though the /24 and /16 also match, longest-prefix match prefers the narrowest route.

This is a direct route-selection question. It reinforces that the router chooses the route that describes the destination most precisely.

Answer

10.50.0.0/16

Answer

10.50.10.0/24

Answer

The default route

Question 8

A router has routes to 192.168.0.0/16 and 192.168.50.0/24. Which route is used for traffic to 192.168.50.99?

Accepted Answer

192.168.50.0/24. The 192.168.50.0/24 route is used because it is more specific. In practical terms, even though the /16 also matches, the router always prefers the route that describes the destination more narrowly. Since 192.168.50.99 falls inside the /24, longest-prefix match chooses that entry.

This is a basic but essential routing rule. The broader /16 still matters for other destinations in 192.168.0.0/16, but not for this one.

Answer

192.168.0.0/16

Answer

The default route

Answer

Both routes equally

Question 9

Why is a default route often described as a route of last resort?

Accepted Answer

Because it is used only when no more specific route matches.. It is described that way because it is used only when no more specific route matches the destination. In practical terms, the router checks for connected, static, or dynamic routes that describe the destination more precisely. If it finds none, the default route becomes the fallback path.

This phrase captures the default route’s purpose exactly. It is not the fastest route or the most specific route. It is simply the catch-all route for otherwise unknown destinations.

Answer

Because it always has the lowest bandwidth.

Answer

Because it is more specific than any other route.

Answer

Because it can be learned only through OSPF.

Question 10

R1 and R2 are directly connected and both configured for OSPF area 0. The IP addresses are correct, but the routers do not become neighbors. What is the most likely cause?

Accepted Answer

The OSPF network types on the interfaces do not match.. The most likely cause is an OSPF network type mismatch. In practical terms, both routers are on the same IP segment and both are trying to use OSPF in the same area, but they do not agree on the type of OSPF network the interface represents. That matters because OSPF behavior changes depending on the network type, including how neighbors are discovered and how adjacencies are formed.

This is a classic exam-style troubleshooting case because the obvious items look correct: IP addressing works and the area matches. But a mismatch between point-to-point and broadcast expectations can still stop the relationship from forming cleanly. That makes network type mismatch the strongest answer here.

Answer

The routers need matching hostnames to exchange LSAs.

Answer

The /30 subnet is too small for OSPF to operate.

Answer

The interfaces must be converted into switch trunks.

Question 11

A router learns the same destination prefix from OSPF and from a static route configured with administrative distance 90. Which route is preferred by default?

Accepted Answer

The static route with distance 90. The static route is preferred because its administrative distance of 90 is lower than OSPF’s default administrative distance of 110. In practical terms, when the prefix length is the same, the router compares route-source trust next. The lower administrative distance wins.

This question is important because many learners remember that static routes are often strong choices but forget that administrative distance can be tuned. Here, that tuning explicitly makes the static route more preferred than OSPF.

Answer

The OSPF route, because dynamic routes always beat static routes

Answer

Both routes equally, because the prefix is identical

Answer

Neither route, because duplicate information is dropped

Question 12

Two directly connected routers running OSPFv3 do not form an adjacency. Both interfaces have valid IPv6 addresses and can ping each other using link-local addresses. What is the most likely cause?

Accepted Answer

The interfaces are assigned to different OSPFv3 areas.. The most likely cause is an OSPFv3 area mismatch on the interface. In practical terms, OSPFv3 still requires neighbors on the same link to agree on the area assignment, just as OSPF for IPv4 does. Link-local reachability alone is not enough to form an adjacency. The protocol parameters still have to match.

This is an important IPv6 routing point because people sometimes assume that successful IPv6 ping means the routing protocol should automatically work. It does not. Adjacency depends on protocol alignment, not just basic connectivity.

Answer

The routers need global unicast addresses before OSPFv3 can run.

Answer

The router IDs must be identical before adjacency can form.

Answer

The link-local addresses must be learned from DHCPv6.

Question 13

A router has a static default route with administrative distance 250 and also learns a default route through OSPF. What is the main design purpose of the static default route?

Accepted Answer

To serve as a backup default route if the OSPF default is lost.. The main purpose is to act as a backup route of last resort if the OSPF-learned default route disappears. In practical terms, the very high administrative distance keeps the static default out of the active table while the OSPF default is available. It remains in reserve only for failure conditions.

This is a classic floating-static-default design. It provides resilience without replacing the primary dynamic path.

Answer

To override the OSPF default route immediately.

Answer

To make the router ignore all default routes.

Answer

To turn the default route into a host route.

Question 14

A router learns 192.168.30.0/24 from OSPF and also has a static route to 192.168.30.0/24 with administrative distance 200. Which route is installed in the routing table while both are available?

Accepted Answer

The OSPF route. The OSPF route is installed because its default administrative distance of 110 is lower than the static route’s configured administrative distance of 200. In practical terms, the static route has been intentionally made a backup. It is present in the configuration, but it does not become active while the lower-distance OSPF route is healthy.

This is a classic floating-static design question. The important point is that route-source preference depends on administrative distance when the prefix length is the same.

Answer

The static route

Answer

Both routes equally for load balancing

Answer

Neither route, because they conflict

Question 15

Which two statements accurately describe floating static routes?

Accepted Answer

They are static routes configured with higher administrative distance so they act as backups.. The two correct statements describe floating static routes as backup routes with higher administrative distance that activate when the preferred route is lost. Option C is wrong because floating static routes have a higher administrative distance, so they do not override dynamic routes immediately; they only activate if the dynamic route is lost. Option D is wrong because floating static routes are for backup, not equal-cost load balancing. Option E is wrong because floating static routes are entries in the routing table that provide backup, not a replacement for it.

Answer

They always override dynamic routes immediately.

Answer

They are identical to equal-cost load balancing.

Answer

They remove the need for routing tables.