Communicating Between Networks 8-10
Which statement is true about ARP?
ARP entries are cached temporarily
What is an attack using ARP?
ARP poisoning
What two protocols are used to determine the MAC address of a known destination device IP address (IPv4 and IPv6)?
ARP(Address Resolution Protocol, IPv4) ND(Neighbor Discovery, ICMPv6)
Four basic operations of network layer protocols
Addressing end devices - End devices must be configured with a unique IP address for identification on the network. Encapsulation - The network layer encapsulates the protocol data unit (PDU) from the transport layer into a packet. The encapsulation process adds IP header information, such as the IP address of the source (sending) and destination (receiving) hosts. Routing - The network layer provides services to direct the packets to a destination host on another network. To travel to other networks, the packet must be processed by a router. The role of the router is to select the best path and direct packets toward the destination host in a process known as routing De-encapsulation - When the packet arrives at the network layer of the destination host, the host checks the IP header of the packet. If the destination IP address within the header matches its own IP address, the IP header is removed from the packet.
The routing table stores three types of route entries:
Directly-connected networks Remote networks Default route
The dynamic routing protocol will automatically do as follows:
Discover remote networks Maintain up-to-date routing information Choose the best path to destination networks Attempt to find a new best path if the current path is no longer available
Which field is used to detect corruption in the IPv4 header?
Header Checksum
Which field in an IPv6 packet is used by the router to determine if a packet has expired and should be dropped?
Hop Limit
On a network, a default gateway is usually a router with these features:
It has a local IP address in the same address range as other hosts on the local network. It can accept data into the local network and forward data out of the local network. It routes traffic to other networks
What will a Layer 2 switch do when the destination MAC address of a received frame is not in the MAC table?
It will forward the frame out of all ports except for the port at which the frame was received
A router can learn about remote networks in one of two ways
Manually - Remote networks are manually entered into the route table using static routes. Dynamically - Remote routes are automatically learned using a dynamic routing protocol.
To what type of address are ICMPv6 neighbor solicitation messages sent?
Multicast
Which two ICMPv6 messages are used in to determine the MAC address of a known IPv6 address?
Neighbor Advertisement Neighbor Solicitation
ICMPv6 has five services:
Neighbor Solicitation messages Neighbor Advertisement messages Router Solicitation messages Router Advertisement messages Redirect Message
The Network Layer
Or OSI Layer 3, provides services to allow end devices to exchange data across networks.
Two primary addresses assigned to a device on an Ethernet LAN:
Physical Address (MAC address) - Used for NIC to NIC communications on the same Ethernet network. Logical address (the IP address) - Used to send the packet from the source device to the destination device. The destination IP address may be on the same IP network as the source or it may be on a remote network.
What will be the response from the router after the command, "router(config)# hostname portsmouth" is entered?
Portsmouth(config)#
Which field includes common values such as ICMP (1), TCP (6), and UDP (17)?
Protocol
Which router component holds the routing table, ARP cache, and running configuration file?
RAM
Which two ICMPv6 messages are used in SLAAC?
Router Advertisement Router Solicitation
A cybersecurity analyst believes an attacker is spoofing the MAC address of the default gateway to perform a man-in-the-middle attack. Which command should the analyst use to view the MAC address a host is using to reach the default gateway?
arp -a
Which delivery method does not guarantee that the packet will be delivered fully without errors?
best effort
This type of route is also known as a gateway of last resort.
default route
When a router receives a packet, what information must be examined in order for the packet to be forwarded to a remote destination?
destination IP address
Which information is used by routers to forward a data packet toward its destination?
destination IP address
What are the two most commonly referenced fields in an IPv4 packet header that indicate where the packet is coming from and where it is going?
destination IP address source IP address
Company policy requires using the most secure method to safeguard access to the privileged exec and configuration mode on the routers. The privileged exec password is trustknow1. Which of the following router commands achieves the goal of providing the highest level of security?
enable secret trustknow1
What is the term for splitting up an IP packet when forwarding it from one medium to another medium with a smaller MTU?
fragmentation
What is a gateway of last resort?
is used to forward packets whose destination address is not listed in the routing table.
Which is true of the IPv6 header?
it consists of 40 octets it contains 8 header fields
Which action is taken by a Layer 2 switch when it receives a Layer 2 broadcast frame?
it sends the frame to all ports except the port on which it received the frame.
Which command can be used on a Windows host to display the routing table?
netstat-r
Which two commands could be entered on a Windows host to view its IPv4 and IPv6 routing table?
netstat-r route print
Which CLI mode allows users to access all device commands, such as those used for configuration, management, and troubleshooting?
privileged EXEC mode
What is one function of the ARP protocol?
resolving an IPv4 address to a MAC address
Which two ICMPv6 messages are used during the Ethernet MAC address resolution process? (Choose two.)
router solicitation & neighbor advertisement
Which command could be used on a Cisco Router to view its ARP table?
show ip arp
Which command can be used on a Cisco router to display all interfaces, the IPv4 address assigned, and the current status?
show ip interface brief
What is the command used on a Cisco IOS router to view the routing table?
show ip route
What information is added during encapsulation at OSI Layer 3?
source and destination IP address
When an IPv4 packet is sent to a host on a remote network, what information is provided by ARP?
the MAC address of the router interface closest to the sending host
Which characteristic describes the default gateway of a host computer?
the logical address of the router interface on the same network as the host computer
What is stored in the NVRAM of a Cisco router?
the startup configuration
ARP provides two basic functions
- Resolving IPv4 addresses to MAC addresses - Maintaining a table of IPv4 to MAC address mappings
Which IPv4 address can a host use to ping the loopback interface?
127.0.0.1
Static routing has the following characteristics:
A static route must be configured manually. The administrator needs to reconfigure a static route if there is a change in the topology and the static route is no longer viable. A static route is appropriate for a small network and when there are few or no redundant links.
Which statement regarding the service password-encryptioncommand is true?
As soon as the service password-encryption command is entered, all currently set passwords formerly displayed in plain text are encrypted
Basic characteristics of IP
Connectionless - There is no connection with the destination established before sending data packets. Best Effort - IP is inherently unreliable because packet delivery is not guaranteed. Media Independent - Operation is independent of the medium (i.e., copper, fiber-optic, or wireless) carrying the data.
Which layer is responsible for taking an IP packet and preparing it for transmission over the communications medium
Data link layer
Which field in an IPv4 packet header will typically stay the same during its transmission?
Destination Address
Which destination address is used in an ARP request frame?
FFFF.FFFF.FFFF.
Which three options are major issues associated with IPv4?
IP address depletion Increased network complexity and internet routing table expansion lack of end-to-end connectivity
What type of information is contained in an ARP table?
IPv4 address to MAC address mappings
What addresses are mapped by ARP?
IPv4 address to a destination MAC address
Which statement accurately describes a characteristic of IPv4?
IPv4 has a 34-bit address space.
Which two options are improvements by IPv6 as compared to IPv4?
Increased the IP address space uses a simpler header to provide improved packet handling
What is the purpose of the banner motd command?
It provides a way to make announcements to those who log in to a router
A host can send a packet to the following:
Itself Local host Remote host
Common route source codes:
L - Directly connected local interface IP address C - Directly connected network S - Static route was manually configured by an administrator O - Open shortest path first D - Enhanced interior gateway routing protocol
The ARP table in a switch maps which two types of address together?
Layer 3 address to a Layer 2 address
Which statement about host forwarding is true?
Local hosts can reach each other without the need of a router
Where is the ARP table stored on a device?
RAM
An administrator is configuring a new router to permit out-of-band management access. Which set of commands will allow the required login using a password of cisco?
Router(config)# line console 0 Router(config-line)# password Cisco
Which command is used to encrypt all passwords in a router configuration file?
Router_A(config)#service password-encryption
Which characteristic describes an IPv6 enhancement over IPv4?
The IPv6 header is simpler than the IPv4 header is, which improves packet handling
What destination MAC address would be included in a frame sent from a source device to a destination device on the same local network
The MAC address of the destination device
What destination MAC address would be included in a Fram sent from a source device to a destination device on a remote local network?
The MAC address of the local router interface
How does the network layer use the MTU value? (maximum transmission unit: largest protocol data PDU that can be communicated in a single network)
The MTU is passed to the network layer by the data link layer
A router boots and enters setup mode. What is the reason for this?
The configuration file is missing from NVRAM
Which default gateway statement is true?
The default gateway address is the IP address of the router on the local network.
Which is true of the IPv6 packet header?
The hop limit field replaces the IPv4 time to live field
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 directly to the destination host
Which statement is correct about IPv4 packet header fields?
The source and destination IPv4 addresses remain the same while traveling from source to destination
Directly-connected networks
These network route entries are active router interfaces. Routers add a directly connected route when an interface is configured with an IP address and is activated. Each router interface is connected to a different network segment. In the figure, the directly-connected networks in the R1 IPv4 routing table would be 192.168.10.0/24 and 209.165.200.224/30.
Remote networks
These network route entries are connected to other routers. Routers learn about remote networks either by being explicitly configured by an administrator or by exchanging route information using a dynamic routing protocol.
Which is a characteristic of static routes?
They are manually configured
A PC is configured to obtain an IPv4 address automatically from network 192.168.1.0/24. The network administrator issues the arp -acommand and notices an entry of 192.168.1.255 ff-ff-ff-ff-ff-ff. Which statement describes this entry?
This is a static map entry
How does the ARP process use an IPv4 address?
To determine the MAC address of a device on the same network
Which OSI layer sends segments to be encapsulated in an IPv4 or IPv6 packet?
Transport layer
True or False? A router can be configured with a combination of both static routes and a dynamic routing protocol.
True
When a connectionless protocol is in use at a lower layer of the OSI model, how is missing data detected and retransmitted if necessary?
Upper-layer connection-oriented protocols keep track of the data received and can request retransmission from the upper-level protocols on the sending host.
What does a code of "O" indicate next to a route in the routing table?
a route learned dynamically from OSPF
A technician is configuring a router to allow for all forms of management access. As part of each different type of access, the technician is trying to type the command login. Which configuration mode should be entered to do this task?
any line configuration mode
What is the purpose of the startup configuration file on a Cisco router?
to contain the commands that are used to initially configure a router
What is the purpose of ARP in an IPv4 network?
to obtain a specific MAC address when an IP address is known
What was the reason for the creation and implementation of IPv6?
to relieve IPv4 address depletion
