14.6.2 Module Quiz – Routing Concepts Answers
1. Which feature on a Cisco router permits the forwarding of traffic for which there is no specific route?
- gateway of last resort
- outgoing interface
- route source
Explanation: A default static route is used as a gateway of last resort to forward unknown destination traffic to a next hop/exit interface. The next-hop or exit interface is the destination to send traffic to on a network after the traffic is matched in a router. The route source is the location a route was learned from.
2. Which three advantages are provided by static routing? (Choose three.)
- Static routing does no advertise over the network, thus providing better security.
- No intervention is required to maintain changing route information.
- Static routes scale well as the network grows.
- The path a static route uses to send data is known.
- Configuration of static routes is error-free.
- Static routing typically uses less network bandwidth and fewer CPU operations than dynamic routing does.
Explanation: Static routes are prone to errors from incorrect configuration by the administrator. They do not scale well, because the routes must be manually reconfigured to accommodate a growing network. Intervention is required each time a route change is necessary. They do provide better security, use less bandwidth, and provide a known path to the destination.
3. What are two functions of dynamic routing protocols? (Choose two.)
- to discover the network
- to avoid exposing network information
- to assure low router overhead
- to choose the path that is specified by the administrator
- to maintain routing tables
Explanation: Dynamic routing protocols exist to discover the network, maintain routing tables, and calculate the best path. Having low levels of routing overhead, using the path specified by the administrator, and avoiding the exposure of network information are functions of static routing.
4. What is an advantage of using dynamic routing protocols instead of static routing?
- fewer router resource overhead requirements
- easier to implement
- more secure in controlling routing updates
- ability to actively search for new routes if the current path becomes unavailable
Explanation: Dynamic routing has the ability to search and find a new best path if the current path is no longer available. The other options are actually the advantages of static routing.
5. Which value represents the “trustworthiness” of a route and is used to determine which route to install into the routing table when there are multiple routes toward the same destination?
- outgoing interface
- routing protocol
- administrative distance
Explanation: The administrative distance represents the trustworthiness of a particular route. The lower an administrative distance, the more trustworthy the learned route is. When a router learns multiple routes toward the same destination, the router uses the administrative distance value to determine which route to place into the routing table. A metric is used by a routing protocol to compare routes received from the routing protocol. An exit interface is the interface used to send a packet in the direction of the destination network. A routing protocol is used to exchange routing updates between two or more adjacent routers.
6. Which packet-forwarding method does a router use to make switching decisions when it is using a forwarding information base and an adjacency table?
- fast switching
- process switching
- Cisco Express Forwarding
- flow process
Explanation: Cisco Express Forwarding (CEF) is the fastest and preferred switching method. It uses a FIB and an adjacency table to perform the task of packet switching. These data structures change with the topology.
7. Which type of route would typically be used on a border router so that devices inside the company could access the Internet?
- directly connected
Explanation: A default route is commonly used on the edge router of a company to connect to an ISP. A default route is a specialized static route that uses the network number and mask of all 0s (0.0.0.0 0.0.0.0). For this reason, it is sometimes known as a quad zero route.
8. What are two functions of a router? (Choose two.)
- It provides segmentation at Layer 2.
- A router connects multiple IP networks.
- It determines the best path to send packets.
- It builds a routing table based on ARP requests.
- It controls the flow of data via the use of Layer 2 addresses.
Explanation: Routers connect multiple networks, determine the best path to send packets, and forward packets based on a destination IP address.
9. When a router learns that multiple paths are available to a destination network from the same routing protocol, which factor is considered by a router to choose the best path to forward a packet?
- the reliability value of the neighboring routers
- the fastest bandwidth of exiting interfaces
- the lowest metric
- the order of paths on the routing table
Explanation: When a router learns that multiple paths are available to a destination network from the same routing protocol, the route with the lowest metric is put into the routing table to forward packets toward that network.
10. Which two route source codes are automatically created within a routing table whenever a router interface is configured with an IP address and activated? (Choose two.)
Explanation: Directly connected and local routes are automatically created whenever an interface is configured with an IP address and activated.
11. The output of the show ip route command contains the following entry:
S 10.2.0.0 [1/0] via 172.16.2.2.
What value is indicated by the 1 in the [1/0] portion of the output?
- interface ID through which the network can be reached
- number of hops
- administrative distance
Explanation: In the routing table entry, S 10.2.0.0 [1/0] via 172.16.2.2, the numbers inside the bracket indicate the administrative distance and metric respectively.
12. Which type of static route creates a gateway of last resort?
- summary static route
- standard static route
- floating static route
- default static route
Explanation: There are four basic types of static routes. Floating static routes are backup routes that are placed into the routing table if a primary route is lost. A summary static route aggregates several routes into one, reducing the size of the routing table. Standard static routes are entered manually into the routing table. Default static routes create a gateway of last resort.
13. What are two common types of static routes in routing tables? (Choose two)
- a static route converted from a route that is learned through a dynamic routing protocol
- a static route to a specific network
- a default static route
- a static route shared between two neighboring routers
- a built-in static route by IOS
Explanation: There are two common types of static routes in a routing table, namely, a static route to a specific network and a default static route. A static route configured on a router can be distributed by the router to other neighboring routers. However, the distributed static route will be a little different in the routing table on neighboring routers.
14. What are two reasons why an administrator might choose to use static routing rather than dynamic routing? (Choose two.)
- Static routing uses less router processing and bandwidth.
- Static routing is easier to maintain in large networks.
- Static routing does not require complete knowledge of the whole network.
- Static routing is more secure.
- Static routing is more scalable.
Explanation: Because static routes must be created and changed manually, they require a larger investment of administrative time and do not scale easily. Static routes do not require additional CPU cycles to calculate and advertise routes, and they provide more security because they are not advertised over the network. Proper implementation of static routes requires the administrator to have a complete understanding of the network topology.
15. What address and prefix length is used when configuring an IPv6 default static route?
Explanation: The IPv6 address and prefix for a default static route is ::/0. This represents all zeros in the address and a prefix length of zero.
16. What are two advantages of static routing over dynamic routing? (Choose two.)
- Static routing is more secure because it does not advertise routes to other routers.
- Static routing is relatively easy to configure for large networks.
- Static routing requires very little knowledge of the network for correct implementation.
- Static routing scales well with expanding networks.
- Static routing uses fewer router resources than dynamic routing.
Explanation: Static routing requires a thorough understanding of the entire network for proper implementation. It can be prone to errors and does not scale well for large networks. Static routing uses fewer router resources because no computing is required for updating routes. Static routing can also be more secure because it does not advertise over the network.
17. What type of route allows a router to forward packets even though its routing table contains no specific route to the destination network?
- default route
- destination route
- dynamic route
- generic route
Explanation: A static default route is a catch-all route for all unmatched networks.
18. The network administrator configures the router with the ip route 172.16.1.0 255.255.255.0 172.16.2.2 command. How will this route appear in the routing table?
- C 172.16.1.0 [1/0] via 172.16.2.2
- C 172.16.1.0 is directly connected, Serial0/0
- S 172.16.1.0 [1/0] via 172.16.2.2
- S 172.16.1.0 is directly connected, Serial0/0
Explanation: The route will appear in the routing with a code of S (Static).
19. R1 is configured with the ip route 10.1.0.0 255.255.0.0 g0/0/0 command. What happens if the G0/0/0 interface goes down?
- The manually configured route remains in the routing table.
- The router polls neighbors for a replacement route.
- The router redirects the static route to a backup interface.
- The static route is removed from the routing table.
Explanation: When the interface associated with a static route goes down, the router will remove the route because it is no longer valid.
20. What static route identifies the gateway IP address to which the router sends all IP packets for which it does not have a learned route?
- Default static route
- Floating static route
- Generic static route
- Summary static route
Explanation: A default static route is a route that matches all packets. It identifies the gateway IP address to which the router sends all IP packets for which it does not have a learned or static route. A default static route is simply a static route with 0.0.0.0/0 as the destination IPv4 address or ::/0 for IPv6. Configuring a default static route creates a gateway of last resort.
21. On which type of network would a dynamic routing protocol be implemented in?
- On a home network router with wireless clients.
- On a network that commonly experiences topology changes.
- On a small two router network.
- On a stub network connecting to a provider.
Explanation: Dynamic routing protocols consume more router resources, are suitable for larger networks, and are more useful on networks that are growing and changing.
22. Which value in a routing table is used to compare routes received from a routing protocol?
- administrative distance
- outgoing interface
- routing protocol
Explanation: A metric is used by a routing protocol to compare routes received from the routing protocol. An exit interface is the interface used to send a packet in the direction of the destination network. A routing protocol is used to exchange routing updates between two or more adjacent routers. The administrative distance represents the trustworthiness of a particular route. The lower an administrative distance, the more trustworthy the learned route is. When a router learns multiple routes toward the same destination, the router uses the administrative distance value to determine which route to place into the routing table.
23. A network administrator configures the G0/0/0 interface with the ip address 10.1.1.0 255.255.255.0 command. However, when the administrator issues the show ip route command, the routing table does not show the directly connected network. What is the possible cause of the problem?
- No packets with a destination network of 172.16.1.0 have been sent to R1.
- The configuration needs to be saved first.
- The G0/0/0 interface has not been activated.
- The subnet mask is incorrect for the IPv4 address.
Explanation: A directly connected network will be added to the routing table when these three conditions are met: (1) the interface is configured with a valid IP address; (2) it is activated with the no shutdown command; and (3) it receives a carrier signal from another device that is connected to the interface. An incorrect subnet mask for an IPv4 address will not prevent its appearance in the routing table, although the error may prevent successful communications.