Module 3.3.3 Network Layer Quiz Answers
Network Addressing and Basic Troubleshooting – Module 3.3.3 Network Layer Quiz Answers
1. A computer can access devices on the same network but cannot access devices on other networks. What is the probable cause of this problem?
- The cable is not connected properly to the NIC.
- The computer has an invalid IP address.
- The computer has an incorrect subnet mask.
- The computer has an invalid default gateway address.
Explanation: The default gateway is the address of the device a host uses to access the Internet or another network. If the default gateway is missing or incorrect, that host will not be able to communicate outside the local network. Because the host can access other hosts on the local network, the network cable and the other parts of the IP configuration are working.
2. What information does the loopback test provide?
- The TCP/IP stack on the device is working correctly.
- The device has end-to-end connectivity.
- DHCP is working correctly.
- The Ethernet cable is working correctly.
- The device has the correct IP address on the network.
Explanation: Because the loopback test sends packets back to the host device, it does not provide information about network connectivity to other hosts. The loopback test verifies that the host NIC, drivers, and TCP/IP stack are functioning.
3. Which two commands can be used on a Windows host to display the routing table? (Choose two.)
- netstat -s
- route print
- show ip route
- netstat -r
Explanation: On a Windows host, the route print or netstat -r commands can be used to display the host routing table. Both commands generate the same output. On a router, the show ip route command is used to display the routing table. The netstat –s command is used to display per-protocol statistics. The tracert command is used to display the path that a packet travels to its destination.
4. During the process of forwarding traffic, what will the router do immediately after matching the destination IP address to a network on a directly connected routing table entry?
- discard the traffic after consulting the route table
- look up the next-hop address for the packet
- switch the packet to the directly connected interface
- analyze the destination IP address
Explanation: A router receives a packet on an interface and looks at the destination IP address. It consults its routing table and matches the destination IP address to a routing table entry. The router then discovers that it has to send the packet to the next-hop address or out to a directly connected interface. When the destination address is on a directly connected interface, the packet is switched over to that interface.
5. A router receives a packet from the Gigabit 0/0 interface and determines that the packet needs to be forwarded out the Gigabit 0/1 interface. What will the router do next?
- route the packet out the Gigabit 0/1 interface
- create a new Layer 2 Ethernet frame to be sent to the destination
- look into the ARP cache to determine the destination IP address
- look into the routing table to determine if the destination network is in the routing table
Explanation: Once a router receives a packet and looks inside the header to determine the destination network, the router compares the destination network to the routing table to determine if the packet is to be routed or dropped. If routed, the router attaches a new Layer 2 header based on the technology that is used by the outgoing port that is used. The packet is then routed out the destination port as designated by the routing table. The ARP cache is used to match an IP address with a MAC address.
6. What type of route is indicated by the code C in an IPv4 routing table on a Cisco router?
- static route
- default route
- directly connected route
- dynamic route that is learned through EIGRP
Explanation: Some of the IPv4 routing table codes include the following:
- C directly connected
- S static
- D EIGRP
- * – candidate default
7. When a router receives a packet, what information must be examined in order for the packet to be forwarded to a remote destination?
- destination MAC address
- source IP address
- destination IP address
- source MAC address
Explanation: When a router receives a packet, it examines the destination address of the packet and uses the routing table to search for the best path to that network.
8. What type of route is created when a network administrator manually configures a route that has an active exit interface?
- directly connected
Explanation: A static route is one that is manually configured by the network administrator.
9. If a company has decided not to use static routing for the four routers inside the company, what would be an alternative solution?
- Use DHCP.
- Install a routing protocol.
- Use automatic flow labels.
- Allow the internet provider to do the routing.
Explanation: There are two basic types of routing: static and dynamic. Static routing occurs when routes are manually entered. Dynamic routing makes use of a routing protocol that is configured and maintained by the company.
10. Which two statements describe features of an IPv4 routing table on a router? (Choose two.)
- The netstat -r command can be used to display the routing table of a router.
- Directly connected interfaces will have two route source codes in the routing table: C and S.
- The routing table stores information about routes derived from the active router interfaces.
- If a default static route is configured in the router, an entry will be included in the routing table with source code S.
- The routing table lists the MAC addresses of each active interface.
Explanation: The show ip route command is used to display the routing table of the router. In IPv4, directly connected interfaces will have one source code:C. The routing table stores information about directly connected routes and remote routes. An entry in the routing table with a source code of S is included if a default static route is configured on the router.
11. A router is receiving a stream of incoming packets that does not contain a route to the remote destination network. What configuration can a network administrator issue in order to successfully forward the incoming packets?
- Add a default route.
- Enable a dynamic routing protocol.
- Share the routing table with the hosts on the local network.
- Change the IP address of the ingress interface to match the targeted destination network.
Explanation: A router contains a routing table of all locally connected networks and the interfaces that connect to them. The routing tables can also contain the routes that the router uses to reach remote networks. Entries can be made to the routing table in two ways. The first is that the router via the use of a routing protocol can be dynamically updated by information received from other routers in the network. The second is that the entries can be manually entered by a network administrator. If the router cannot determine where to forward a packet, it will drop it. Network administrators can configure a default route to keep a packet from being dropped because the path to the destination network is not in the routing table. A default route is the interface through which the router forwards a packet containing an unknown destination IP network address.
12. Which address should be configured as the default gateway address of a client device?
- the Layer 2 address of the switch management interface
- the Layer 2 address of the switch port that is connected to the workstation
- the IPv4 address of the router interface that is connected to the same LAN
- the IPv4 address of the router interface that is connected to the internet
Explanation: The default gateway is used when a host needs to send messages to destinations that are located in remote networks. The default gateway address is configured on the host with the IPv4 address of the router interface that is connected to the same local network as the host.