CCNA 1 v7 Modules 8 – 10: Communicating Between Networks Exam Answers Flashcards
Which information is used by routers to forward a data packet toward its destination?
source IP address
destination IP address
source data-link address
destination data-link address
destination IP address
A computer has to send a packet to a destination host in the same LAN. How will the packet be sent?
The packet will be sent to the default gateway first, and then, depending on the response from the gateway, it may be sent to the destination host.
The packet will be sent directly to the destination host.
The packet will first be sent to the default gateway, and then from the default gateway it will be sent directly to the destination host.
The packet will be sent only to the default gateway.
The packet will be sent directly to the destination host.
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
create a new Layer 2 Ethernet frame to be sent to the destination
Which IPv4 address can a host use to ping the loopback interface?
126.0.0.1
127.0.0.0
126.0.0.0
127.0.0.1
127.0.0.1
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.
The computer has an invalid default gateway address.
Which parameter does the router use to choose the path to the destination when there are multiple routes available?
the lower metric value that is associated with the destination network
the lower gateway IP address to get to the destination network
the higher metric value that is associated with the destination network
the higher gateway IP address to get to the destination network
the lower metric value that is associated with the destination network
Which statement describes a feature of the IP protocol?
IP encapsulation is modified based on network media.
IP relies on Layer 2 protocols for transmission error control.
MAC addresses are used during the IP packet encapsulation.
IP relies on upper layer services to handle situations of missing or out-of-order packets.
IP relies on upper layer services to handle situations of missing or out-of-order packets.
Explanation: IP protocol is a connection-less protocol, considered unreliable in terms of end-to-end delivery. It does not provide error control in the cases where receiving packets are out-of-order or in cases of missing packets. It relies on upper layer services, such as TCP, to resolve these issues.
Why is NAT not needed in IPv6?
Because IPv6 has integrated security, there is no need to hide the IPv6 addresses of internal networks.
Any host or user can get a public IPv6 network address because the number of available IPv6 addresses is extremely large.
The problems that are induced by NAT applications are solved because the IPv6 header improves packet handling by intermediate routers.
The end-to-end connectivity problems that are caused by NAT are solved because the number of routes increases with the number of nodes that are connected to the Internet.
Any host or user can get a public IPv6 network address because the number of available IPv6 addresses is extremely large.
Explanation: The large number of public IPv6 addresses eliminates the need for NAT. Sites from the largest enterprises to single households can get public IPv6 network addresses. This avoids some of the NAT-induced application problems that are experienced by applications that require end-to-end connectivity.
Within a production network, what is the purpose of configuring a switch with a default gateway address?
Hosts that are connected to the switch can use the switch default gateway address to forward packets to a remote destination.
A switch must have a default gateway to be accessible by Telnet and SSH.
The default gateway address is used to forward packets originating from the switch to remote networks.
It provides a next-hop address for all traffic that flows through the switch.
The default gateway address is used to forward packets originating from the switch to remote networks.
Explanation: A default gateway address allows a switch to forward packets that originate on the switch to remote networks. A default gateway address on a switch does not provide Layer 3 routing for PCs that are connected on that switch. A switch can still be accessible from Telnet as long as the source of the Telnet connection is on the local network.
What are two services provided by the OSI network layer? (Choose two.)
performing error detection
routing packets toward the destination
encapsulating PDUs from the transport layer
placement of frames on the media
collision detection
routing packets toward the destination
encapsulating PDUs from the transport layer
Explanation: The OSI network layer provides several services to allow communication between devices:
addressing
encapsulation
routing
de-encapsulation
Error detection, placing frames on the media, and collision detection are all functions of the data ink layer.
What IPv4 header field identifies the upper layer protocol carried in the packet?
Protocol
Identification
Version
Differentiated Services
Protocol
Explanation: It is the Protocol field in the IP header that identifies the upper-layer protocol the packet is carrying. The Version field identifies the IP version. The Differential Services field is used for setting packet priority. The Identification field is used to reorder fragmented packets.
Which field in the IPv4 header is used to prevent a packet from traversing a network endlessly?
Time-to-Live
Sequence Number
Acknowledgment Number
Differentiated Services
Time-to-Live
Explanation: The value of the Time-to-Live (TTL) field in the IPv4 header is used to limit the lifetime of a packet. The sending host sets the initial TTL value; which is decreased by one each time the packet is processed by a router. If the TTL field decrements to zero, the router discards the packet and sends an Internet Control Message Protocol (ICMP) Time Exceeded message to the source IP address. The Differentiated Services (DS) field is used to determine the priority of each packet. Sequence Number and Acknowledgment Number are two fields in the TCP header.
n/a
n/a
What is a basic characteristic of the IP protocol?
connectionless
media dependent
user data segmentation
reliable end-to-end delivery
connectionless
Explanation: Internet Protocol (IP) is a network layer protocol that does not require initial exchange of control information to establish an end-to-end connection before packets are forwarded. Thus, IP is connectionless and does not provide reliable end-to-end delivery by itself. IP is media independent. User data segmentation is a service provided at the transport layer.
What is one advantage that the IPv6 simplified header offers over IPv4?
smaller-sized header
little requirement for processing checksums
smaller-sized source and destination IP addresses
efficient packet handling
efficient packet handling
Explanation: The IPv6 simplified header offers several advantages over IPv4:
Better routing efficiency and efficient packet handling for performance and forwarding-rate scalability
No requirement for processing checksums
Simplified and more efficient extension header mechanisms (as opposed to the IPv4 Options field)
A Flow Label field for per-flow processing with no need to open the transport inner packet to identify the various traffic flows
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.
The TCP/IP stack on the device is working correctly.
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.
What routing table entry has a next hop address associated with a destination network?
directly-connected routes
local routes
remote routes
C and L source routes
remote routes
Explanation: Routing table entries for remote routes will have a next hop IP address. The next hop IP address is the address of the router interface of the next device to be used to reach the destination network. Directly-connected and local routes have no next hop, because they do not require going through another router to be reached.
How do hosts ensure that their packets are directed to the correct network destination?
They have to keep their own local routing table that contains a route to the loopback interface, a local network route, and a remote default route.
They always direct their packets to the default gateway, which will be responsible for the packet delivery.
They search in their own local routing table for a route to the network destination address and pass this information to the default gateway.
They send a query packet to the default gateway asking for the best route.
They have to keep their own local routing table that contains a route to the loopback interface, a local network route, and a remote default route.
Explanation: Hosts must maintain their own local routing table to ensure that network layer packets are directed to the correct destination network. This local table typically contains a route to the loopback interface, a route to the network that the host is connected to, and a local default route, which represents the route that packets must take to reach all remote network addresses.
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?
Next Header
Flow Label
Traffic Class
Differentiated Services
Flow Label
Explanation: The Flow Label in IPv6 header is a 20-bit field that provides a special service for real-time applications. This field can be used to inform routers and switches to maintain the same path for the packet flow so that packets will not be reordered.
What statement describes the function of the Address Resolution Protocol?
ARP is used to discover the IP address of any host on a different network.
ARP is used to discover the IP address of any host on the local network.
ARP is used to discover the MAC address of any host on a different network.
ARP is used to discover the MAC address of any host on the local network.
ARP is used to discover the MAC address of any host on the local network.
Explanation: When a PC wants to send data on the network, it always knows the IP address of the destination. However, it also needs to discover the MAC address of the destination. ARP is the protocol that is used to discover the MAC address of a host that belongs to the same network.
Under which two circumstances will a switch flood a frame out of every port except the port that the frame was received on? (Choose two.)
The frame has the broadcast address as the destination address.
The destination address is unknown to the switch.
The source address in the frame header is the broadcast address.
The source address in the frame is a multicast address.
The destination address in the frame is a known unicast address.
The frame has the broadcast address as the destination address.
The destination address is unknown to the switch.
Explanation: A switch will flood a frame out of every port, except the one that the frame was received from, under two circumstances. Either the frame has the broadcast address as the destination address, or the destination address is unknown to the switch.
Which statement describes the treatment of ARP requests on the local link?
They must be forwarded by all routers on the local network.
They are received and processed by every device on the local network.
They are dropped by all switches on the local network.
They are received and processed only by the target device.
They are received and processed by every device on the local network.
Explanation: One of the negative issues with ARP requests is that they are sent as a broadcast. This means all devices on the local link must receive and process the request.
Which destination address is used in an ARP request frame?
0.0.0.0
255.255.255.255
FFFF.FFFF.FFFF
AAAA.AAAA.AAAA
the physical address of the destination host
FFFF.FFFF.FFFF
Explanation: The purpose of an ARP request is to find the MAC address of the destination host on an Ethernet LAN. The ARP process sends a Layer 2 broadcast to all devices on the Ethernet LAN. The frame contains the IP address of the destination and the broadcast MAC address, FFFF.FFFF.FFFF. The host with the IP address that matches the IP address in the ARP request will reply with a unicast frame that includes the MAC address of the host. Thus the original sending host will obtain the destination IP and MAC address pair to continue the encapsulation process for data transmission.
A network technician issues the arp -d * command on a PC after the router that is connected to the LAN is reconfigured. What is the result after this command is issued?
The ARP cache is cleared.
The current content of the ARP cache is displayed.
The detailed information of the ARP cache is displayed.
The ARP cache is synchronized with the router interface.
The ARP cache is cleared.
Explanation: Issuing the arp –d * command on a PC will clear the ARP cache content. This is helpful when a network technician wants to ensure the cache is populated with updated information.
Refer to the exhibit. The exhibit shows a small switched network and the contents of the MAC address table of the switch. PC1 has sent a frame addressed to PC3. What will the switch do with the frame?
The switch will discard the frame.
The switch will forward the frame only to port 2.
The switch will forward the frame to all ports except port 4.
The switch will forward the frame to all ports.
The switch will forward the frame only to ports 1 and 3.
The switch will forward the frame to all ports except port 4.
Explanation: The MAC address of PC3 is not present in the MAC table of the switch. Because the switch does not know where to send the frame that is addressed to PC3, it will forward the frame to all the switch ports, except for port 4, which is the incoming port.
Which two types of IPv6 messages are used in place of ARP for address resolution?
anycast
broadcast
echo reply
echo request
neighbor solicitation
neighbor advertisement
neighbor solicitation
neighbor advertisement
Explanation: IPv6 does not use ARP. Instead, ICMPv6 neighbor discovery is used by sending neighbor solicitation and neighbor advertisement messages.
What is the aim of an ARP spoofing attack?
to flood the network with ARP reply broadcasts
to fill switch MAC address tables with bogus addresses
to associate IP addresses to the wrong MAC address
to overwhelm network hosts with ARP requests
to associate IP addresses to the wrong MAC address
Explanation: In an ARP spoofing attack, a malicious host intercepts ARP requests and replies to them so that network hosts will map an IP address to the MAC address of the malicious host.
