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Questions and Answers
What statement describes the function of the Address Resolution Protocol?
Which destination address is used in an ARP request frame?
What is the result after issuing the command 'arp -d *'?
The ARP cache is cleared.
Where are IPv4 address to Layer 2 Ethernet address mappings maintained on a host computer?
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What important information is examined in the Ethernet frame header by a Layer 2 device in order to forward the data onward?
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What occurs when the 'copy running-config startup-config' command is entered on a router?
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What is the effect of incorrectly configuring the default gateway address on a host?
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What are two potential network problems resulting from ARP operation?
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What does the 'transport input ssh' command do when entered on the switch vty lines?
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A router primarily forwards packets based on the destination address.
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Which information is used by routers to forward a data packet toward its destination?
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A computer has to send a packet to a destination host in the same LAN. How will the packet be sent?
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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?
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Which IPv4 address can a host use to ping the loopback interface?
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A computer can access devices on the same network but cannot access devices on other networks. What is the probable cause of this problem?
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Which statement describes a feature of the IP protocol?
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Which interfaces in each router are active?
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Which term describes a field in the IPv4 packet header used to identify the next level protocol?
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Which term describes a field in the IPv4 packet header that contains an 8-bit binary value used to determine the priority of each packet?
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Which term describes a field in the IPv4 packet header that contains a 32-bit binary value associated with an interface on the sending device?
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What IP address would be configured as the default gateway on the new host connecting to the Payroll LAN? _______________
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Which term describes a field in the IPv4 packet header that contains a unicast, multicast, or broadcast address?
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What IP address would be configured as the default gateway on the new host connecting to the Service LAN?
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What IP address would be configured as the default gateway on the new host connecting to the Medical LAN?
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What IP address would be configured as the default gateway on the new host connecting to the Registrar LAN?
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What IP address would be configured as the default gateway on the new host connecting to the Manager LAN?
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What IP address would be configured as the default gateway on the new host connecting to the Store LAN?
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Why is NAT not needed in IPv6?
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Which parameter does the router use to choose the path to the destination when there are multiple routes available?
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What are two services provided by the OSI network layer? (Choose two)
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Within a production network, what is the purpose of configuring a switch with a default gateway address?
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What is a basic characteristic of the IP protocol?
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Which field in the IPv4 header is used to prevent a packet from traversing a network endlessly?
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What advantage does the IPv6 simplified header offer over IPv4?
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What IPv4 header field identifies the upper layer protocol carried in the packet?
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What information does the loopback test provide?
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What routing table entry has a next hop address associated with a destination network?
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How do hosts ensure that their packets are directed to the correct network destination?
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When transporting data from real-time applications, such as streaming audio and video, which field in the IPv6 header can be used to inform the routers and switches to maintain the same path for the packets in the same conversation?
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Study Notes
Communicating Between Networks
Routers and Packet Forwarding
- Routers use the destination IP address to forward a data packet towards its destination.
- A router receives a packet from an interface and determines that the packet needs to be forwarded out another interface.
- The router will create a new Layer 2 Ethernet frame to be sent to the destination.
IP Addressing
- A host can use the IP address 127.0.0.1 to ping the loopback interface.
- The large number of public IPv6 addresses eliminates the need for NAT (Network Address Translation).
- Any host or user can get a public IPv6 network address, which avoids some of the NAT-induced application problems.
Routing Decisions
- A router uses the metric value associated with the destination network to choose the path to the destination when there are multiple routes available.
- The metric value is used to determine the best path to the destination network.
OSI Network Layer
- The OSI network layer provides several services, including:
- Addressing
- Encapsulation
- Routing
- De-encapsulation
- Error detection, placing frames on the media, and collision detection are functions of the data link layer.
Switch Configuration
- Configuring a switch with a default gateway address allows the switch to forward packets originating from the switch to remote networks.
- The default gateway address is not used to provide Layer 3 routing for PCs connected to the switch.
IP Protocol Characteristics
- The IP protocol is connectionless, meaning it does not require an initial exchange of control information to establish an end-to-end connection before packets are forwarded.
- IP is media independent and does not provide reliable end-to-end delivery by itself.
- User data segmentation is a service provided at the transport layer.
IPv4 Header Fields
- The Time-to-Live (TTL) field in the IPv4 header is used to limit the lifetime of a packet and prevent it from traversing a network endlessly.
- The Protocol field in the IPv4 header identifies the upper-layer protocol the packet is carrying.
- The Differentiated Services (DS) field is used to determine the priority of each packet.
IPv6 Simplified Header
- The IPv6 simplified header offers several advantages over IPv4, including:
- Better routing efficiency and efficient packet handling
- No requirement for processing checksums
- Simplified and more efficient extension header mechanisms### Routing and Forwarding
- Packets are forwarded through different interfaces based on their destination IP addresses.
- A gateway of last resort is used when there is no entry in the routing table for a packet's destination network.
- If a packet's destination network is unknown, it will be forwarded through the gateway of last resort.
Loopback Test
- The loopback test verifies that the host NIC, drivers, and TCP/IP stack are functioning.
- It does not provide information about network connectivity to other hosts.
Routing Table Entries
- Remote routes have a next hop IP address associated with a destination network.
- Directly-connected and local routes do not require a next hop, as they do not need to go through another router.
Host Routing
- Hosts maintain their own local routing table to ensure packets are directed to the correct destination network.
- The local routing table typically contains a route to the loopback interface, a local network route, and a default route.
IPv6 Header Field
- The Flow Label field in the IPv6 header is used to inform routers and switches to maintain the same path for packets in the same conversation.
Address Resolution Protocol (ARP)
- ARP is used to discover the MAC address of a host on the same network.
- ARP requests are sent as broadcasts to all devices on the local link.
- Switches forward ARP requests to all ports except the incoming port.
ARP Cache
- The ARP cache is used to store IPv4 addresses and their corresponding MAC addresses.
- Clearing the ARP cache using the
arp -d *command is helpful when a router's configuration changes.
IPv6 Address Resolution
- Neighbor solicitation and neighbor advertisement messages are used in place of ARP for address resolution in IPv6.
Network Security
- ARP spoofing attacks associate IP addresses with incorrect MAC addresses.
- The aim of an ARP spoofing attack is to associate an IP address with the wrong MAC address.
Frame Forwarding
- Switches forward frames based on the destination MAC address.
- If a switch does not know where to send a frame, it will forward it to all ports except the incoming port.
Network Device Access
- Console and AUX ports can be used for local management access to network devices.
- SSH and Telnet are remote access methods that depend on an active network connection.
Router Boot Process
- The boot process of a Cisco router involves three phases: performing the POST and loading the bootstrap program, loading the Cisco IOS software, and loading the startup configuration file.
Network Device Management
- The
ip default-gatewaycommand is used to configure a default gateway on a switch. - The
transport input sshcommand enables SSH encryption for remote access to a switch.### CCNA 1 v7 Modules 8-10: Communicating Between Networks
Router Configuration
- The three commands needed to password protect the console port are:
-
line console 0 -
password cisco -
login
-
- The
interface fastethernet 0/0command is used to access the configuration mode for a specific interface (e.g. Fa0/0) - The
line vty 0 4command is used to access the configuration mode for Telnet, specifying ports 0 through 4 (maximum of five simultaneous connections) - The
enable secretcommand is used to apply a password used to access privileged mode on the router
Default Gateway
- The default gateway is the IP address of the first Layer 3 device (router interface) that connects to the same network
- The default gateway is used to route packets destined for remote networks
- If the default gateway is incorrectly configured, the host can communicate with other hosts on the same network, but not with hosts on remote networks
Router Functions
- Two primary functions of a router are:
- Packet forwarding
- Path selection
- A router accepts a packet, accesses its routing table, and determines the appropriate exit interface based on the destination address
Router Configuration Files
- The
copy running-config startup-configcommand copies the running-configuration file from RAM into NVRAM, saving it as the startup-configuration file - This ensures that the configuration details are retained when the router is powered off
ARP Operation
- Two potential network problems that can result from ARP operation are:
- Manually configuring static ARP associations could facilitate ARP poisoning or MAC address spoofing
- Network attackers could manipulate MAC address and IP address mappings in ARP messages with the intent of intercepting network traffic
- Large numbers of ARP broadcast messages could cause momentary data communication delays
IPv4 Packet Header
- The protocol field in the IPv4 packet header is used to identify the next level protocol
- The TTL (Time To Live) field in the IPv4 packet header is used to limit the lifetime of a packet
- The header checksum field in the IPv4 packet header is used to detect corruption in the IPv4 header
- The source IPv4 address field in the IPv4 packet header contains a unicast, multicast, or broadcast address
- The version field in the IPv4 packet header contains a 4-bit binary value set to 0100
ARP Properties
- ARP allows hosts on a LAN to send traffic to remote networks by learning the MAC address of the default gateway
- ARP allows MAC addresses of frequently used servers to be fixed in the ARP table through manual configuration
- ARP forces all Ethernet NICs to process an ARP request when the destination MAC address FF-FF-FF-FF-FF-FF appears in the header of the Ethernet frame
- ARP causes a reply only to the source sending an ARP request
- ARP causes the request to be flooded out all ports of a switch except for the port receiving the ARP request
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Description
This quiz covers the exam answers for CCNA 1 v7 Modules 8-10, focusing on communicating between networks. It's ideal for those studying for the CCNA certification.
