CCNA IP Routing — 20 Questions

Question 1

What is the OSPF metric called?

Accepted Answer

Cost. OSPF uses cost as its internal metric. By default, cost is derived primarily from bandwidth.

Answer

Hop count

Answer

Distance

Answer

Feasible distance

Question 2

What is the effect of route summarization at an area boundary or redistribution point?

Accepted Answer

It combines multiple more-specific routes into a shorter prefix advertisement.. Summarization reduces the number of routes advertised by combining contiguous networks into a shorter prefix.

Answer

It increases the administrative distance of all routes.

Answer

It forces equal-cost load balancing across all paths.

Answer

It prevents the use of a default route.

Question 3

What is the purpose of a default route on a router?

Accepted Answer

To forward packets when no more specific match is found. A default route is used when no more specific route exists in the routing table.

Answer

To replace all directly connected routes

Answer

To advertise only loopback interfaces

Answer

To disable dynamic routing updates

Question 4

What is the main reason a default route is sometimes called a route of last resort?

Accepted Answer

It is used only when no more specific route matches the destination. A default route is called the route of last resort because the router uses it only when no more specific route matches the destination. In plain language, it is the fallback instruction the router follows when it does not have a better answer in the routing table. That makes it extremely useful for branch routers, Internet edge devices, and other places where unknown destinations should simply be sent to an upstream path.

The default route is not “last” because it is slow or because it is dangerous. It is last because it is the least specific match. As soon as the router finds a more specific prefix, that route takes precedence. This is a core route-selection concept and helps explain why default routes work so well alongside more detailed routing information.

Answer

It always has the highest bandwidth link

Answer

It is processed before all connected routes

Answer

It disables all dynamic routing protocols

Question 5

What is the main purpose of route summarization in a routed network?

Accepted Answer

To combine multiple routes into a smaller set of broader advertisements. Route summarization combines multiple more-specific routes into a smaller set of broader advertisements. In plain language, it helps reduce routing-table size and can simplify the information routers exchange with each other. This can improve scalability and reduce churn because the network does not need to advertise every small route individually when a broader summary is appropriate.

Summarization is not about creating VLAN tags or assigning DHCP leases. It is a routing design technique used to make route information more compact and manageable.

Answer

To force every subnet to use the default route only

Answer

To assign IP addresses dynamically to routers

Answer

To convert access ports into trunks

Question 6

What is the main reason route summarization can improve scalability in larger networks?

Accepted Answer

It reduces the number of routes that routers must carry and exchange. Route summarization can improve scalability because it reduces the number of individual routes that must be carried and exchanged. In plain language, instead of advertising many small routes separately, the network can often advertise a smaller set of broader prefixes. That reduces routing-table size and can simplify control-plane behavior. It also helps contain route-change noise in some designs because every small internal change does not necessarily need to be advertised individually as a separate route.

This does not mean summarization fixes every design problem, but it is a classic routing scalability tool. The best answer is the one that focuses on reducing and simplifying route information rather than confusing summarization with NAT, VLANs, or DHCP.

Answer

It forces every packet to use the default route

Answer

It automatically encrypts routing updates

Answer

It converts all access links into routed ports

Question 7

Which statement best describes the role of a router’s routing table?

Accepted Answer

It helps the router choose where to forward packets toward destination networks. A routing table contains the information a router uses to decide where to forward packets toward their destinations. In plain language, it is the router’s map of known networks and next-hop choices. When a packet arrives, the router checks the destination address against the routing table and uses the best matching entry to determine how to move the packet onward.

A routing table is not the same thing as a switch MAC table, and it is not primarily a record of passwords or logs. It is a forwarding decision structure. That is why the correct answer is the one focused on selecting paths to remote networks rather than on switching-only behavior or unrelated management tasks.

Answer

It stores secure user passwords for AAA login

Answer

It maps every MAC address on the LAN to a switch port

Answer

It defines STP root bridge election values

Question 8

What is the main reason a router uses the default route only after checking for more specific routes first?

Accepted Answer

Because the default route is the least specific match and is meant to be a fallback. A router uses the default route only after checking for more specific matches because routing logic is based on longest-prefix match. In plain language, the router prefers the route that most precisely describes the destination network. A default route is the least specific possible match, so it is kept as a fallback rather than a first choice.

That is what makes it useful as a route of last resort.

Answer

Because default routes always have the lowest bandwidth

Answer

Because default routes are processed only after STP converges

Answer

Because default routes can be used only on switches and not routers

Question 9

What is the main reason route administrative distance exists in Cisco routing logic?

Accepted Answer

To rank the trustworthiness of different route sources. Administrative distance exists so the router can rank the trustworthiness of different route sources. In plain language, if the router learns the same destination from multiple sources such as static routing and OSPF, it needs a way to decide which source to trust more before installing the route.

This is different from a metric, which usually compares paths inside one routing protocol. Administrative distance is a cross-source preference tool.

Answer

To identify the MAC address of the next hop

Answer

To determine trunk native VLAN behavior

Answer

To encrypt routing updates between routers

Question 10

Which statement best describes equal-cost multipath behavior in routing?

Accepted Answer

The router may install multiple equally good routes to the same destination and use them for forwarding. Equal-cost multipath allows a router to use more than one path to the same destination when those paths are considered equally good by the routing logic. In plain language, if the router sees multiple valid routes with the same cost or equivalent preference, it may install more than one and share traffic across them. This can improve redundancy and load distribution without requiring one path to sit idle.

This concept is important because learners often assume the router must always choose only one path. In reality, many routing environments support multiple equal paths simultaneously. The correct answer is the one that captures this multi-path forwarding behavior.

Answer

The router always discards all but the first route learned

Answer

Equal-cost multipath means every route source is trusted equally

Answer

Equal-cost multipath works only when no routing table exists

Question 11

What is the main reason a more specific route usually overrides a less specific route, even when both point to valid destinations?

Accepted Answer

Because routing prefers the most specific matching prefix.. A more specific route overrides a less specific route because longest-prefix match is the core logic used for route selection among matching destinations. In plain language, the router prefers the entry that most narrowly and accurately describes the actual destination network. This makes routing behavior precise and predictable, especially when summary routes and more detailed routes coexist.

If routers did not prefer the more specific match, detailed route information would not provide much value. The correct answer is the one that explains route choice in terms of specificity rather than protocol type alone.

Answer

Because less specific routes are always invalid.

Answer

Because more specific routes always have a lower administrative distance.

Answer

Because OSPF requires every route to be /32.

Question 12

Which statement best explains why a router uses longest-prefix match before other route-comparison steps between matching routes?

Accepted Answer

Because the router first prefers the route that most precisely matches the destination.. Longest-prefix match comes first because route specificity is the most direct way to identify the best matching destination range. In plain language, if several routes could all technically match a packet, the router first asks which one describes the destination most precisely. Only after that does it compare other properties among routes of equal prefix length.

This is fundamental to routing-table logic. If the router ignored prefix specificity, detailed route entries would lose much of their value. The correct answer is the one that explains route choice in terms of the most specific valid match.

Answer

Because administrative distance is meaningful only for MAC addresses.

Answer

Because default routes are considered more specific than host routes.

Answer

Because OSPF requires it only on Ethernet links.

Question 13

What is the main operational value of a floating static route in a routed network?

Accepted Answer

It provides a backup route that becomes active if the preferred route is lost.. The main operational value of a floating static route is simple backup routing. In plain language, it gives the router a standby path that can take over automatically if the preferred route disappears, while staying out of the way during normal operation. This is achieved by assigning it a higher administrative distance than the primary route source.

Floating statics are useful because they provide failover without forcing the administrator to remove the primary dynamic design. The correct answer is the one that emphasizes reserve-path behavior rather than immediate preference.

Answer

It always overrides dynamic routing because it is static.

Answer

It removes the need for any default route.

Answer

It converts dynamic routes into connected routes.

Question 14

Which statement best describes the purpose of administrative distance when two different routing sources advertise the same prefix?

Accepted Answer

It ranks the trustworthiness of different route sources advertising the same destination.. Administrative distance helps the router decide which route source to trust more. In plain language, if the same network is learned from two different sources, such as OSPF and a static route, the router needs a source-preference rule before it can install one. Administrative distance provides that rule.

This is different from a metric, which typically compares multiple paths inside the same routing protocol. The correct answer is the one focused on source trust rather than path cost inside one protocol.

Answer

It determines the MAC address of the next hop.

Answer

It specifies the native VLAN for trunk links.

Answer

It defines the subnet mask of the learned route.

Question 15

What is the main operational purpose of a default route on an edge or branch router?

Accepted Answer

To provide a fallback next hop for destinations that do not match any more specific route.. The main purpose of a default route is to provide a fallback path for destinations that do not match any more specific route. In plain language, the router uses it to send unknown or non-local traffic toward an upstream router or Internet connection rather than dropping it immediately. This is especially useful in smaller or edge networks that do not need full visibility of every external route.

A default route does not replace more specific route entries. It complements them by acting as a route of last resort. The correct answer is the one centered on fallback forwarding to an upstream path.

Answer

To make every route in the table equally specific.

Answer

To disable dynamic routing automatically.

Answer

To replace the need for subnet masks on hosts.

Question 16

What is the main purpose of a floating static route in a network that already uses dynamic routing?

Accepted Answer

It acts as a backup path that becomes active if the preferred dynamic route is lost.. A floating static route provides a standby backup path without replacing the preferred dynamic route during normal operation. In plain language, it sits in reserve because its administrative distance is set higher than the primary route source. If the dynamic route disappears, the floating static route can take over automatically.

This is valuable because it adds simple backup behavior without forcing the administrator to abandon the dynamic design. The correct answer is the one focused on backup failover rather than immediate preference.

Answer

It always overrides the dynamic route because static routes are preferred by definition.

Answer

It removes the need for administrative distance.

Answer

It converts dynamic routes into connected routes.

Question 17

What is the main reason administrators use floating static routes in networks that already run dynamic routing protocols?

Accepted Answer

To provide a backup route that takes over if the preferred dynamic route is lost.. Administrators use floating static routes to provide simple backup paths without replacing the preferred dynamic routes during normal operation. In plain language, the static route is intentionally given a higher administrative distance so it stays inactive until the better route disappears. That makes failover possible without changing the normal routing design.

This is a very practical design technique. The correct answer is the one centered on backup behavior rather than on immediate preference.

Answer

To force static routing to override the dynamic protocol all the time.

Answer

To eliminate the need for routing metrics entirely.

Answer

To convert default routes into connected routes.

Question 18

What is the main value of route summarization at a distribution layer or area boundary?

Accepted Answer

It reduces the number of individual routes that must be advertised or stored.. Route summarization reduces the number of specific prefixes that need to be advertised or carried. In practical terms, instead of sending many small route entries, the network can often advertise one broader summary that represents them. That helps control routing-table growth and simplifies the control plane, especially at aggregation points.

Summarization does not eliminate the need for detail everywhere, but it is an important scaling technique. The strongest answer is the one focused on route reduction and manageability.

Answer

It forces every subnet to use only a default route.

Answer

It automatically encrypts route updates.

Answer

It removes the need for subnet masks.

Question 19

What is the main operational benefit of summarizing multiple routes into one broader prefix where appropriate?

Accepted Answer

It reduces the number of specific routes that must be carried or advertised.. The main benefit is that it reduces the number of route entries that must be advertised and stored. In practical terms, one broader summary can stand in for many smaller prefixes. That simplifies the routing table and can improve scalability, especially at aggregation points.

Summarization does not eliminate all specific routing everywhere, but it helps keep the control plane cleaner. That is why it is widely used at distribution layers and routing boundaries.

Answer

It guarantees every packet uses only the default route.

Answer

It automatically encrypts route updates.

Answer

It removes the need for subnet masks.

Question 20

What is the main reason a default route is useful on a small branch router with a single upstream connection?

Accepted Answer

It provides a simple next hop for unknown destinations toward the upstream connection.. A default route is useful because it gives the branch a simple fallback path for any destination the router does not know specifically. In practical terms, the branch does not need to learn every possible remote prefix if all unknown traffic should simply be sent to the one upstream router or ISP connection.

This is why default routes are common in small sites and edge designs. They simplify the routing table while still allowing off-site communication.

Answer

It makes every route more specific.

Answer

It removes the need for addressing on the router.

Answer

It forces all hosts into one VLAN.