v1 mod7
What is the purpose of the FCS field in a frame?
-to obtain the MAC address of the sending node
-to verify the logical address of the sending node
-to compute the CRC header for the data field
-to determine if errors occurred in the transmission and reception
what is
to determine if errors occurred in the transmission and reception
The FCS field in a frame is used to detect any errors in the transmission and receipt of a frame. This is done by comparing the CRC value within the frame against a computed CRC value of the frame. If the two values do not match, then the frame is discarded.
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1.7.1 Ethernet Frames
What is the auto-MDIX feature?
-It enables a device to automatically configure an interface to use a straight-through or a crossover cable.
-It enables a device to automatically configure the duplex settings of a segment.
-It enables a device to automatically configure the speed of its interface.
-It enables a switch to dynamically select the forwarding method
what is
It enables a device to automatically configure an interface to use a straight-through or a crossover cable.
The auto-MDIX feature allows the device to configure its network port according to the cable type that is used (straight-through or crossover) and the type of device that is connected to that port. When a port of a switch is configured with auto-MDIX, this switch can be connected to another switch by the use of either a straight-through cable or a crossover cable.
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1.7.4 Switch Speeds and Forwarding Methods
What is a basic characteristic of the IP protocol?
-connectionless
-media dependent
-user data segmentation
-reliable end-to-end delivery
what is
connectionless
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.
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1.8.1 Network Layer Characteristics
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
what is
time-to-live
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.
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1.8.2 IPv4 Packet
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.
what is
ARP is used to discover the MAC address of any host on the local network.
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.
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1.9.2 ARP
What is the auto-MDIX feature on a switch?
-the automatic configuration of an interface for 10/100/1000 Mb/s operation
-the automatic configuration of an interface for a straight-through or a crossover Ethernet cable connection
-the automatic configuration of full-duplex operation over a single Ethernet copper or optical cable
-the ability to turn a switch interface on or off accordingly if an active connection is detected
what is
the automatic configuration of an interface for a straight-through or a crossover Ethernet cable connection
The auto-MDIX enables a switch to use a crossover or a straight-through Ethernet cable to connect to a device regardless of the device on the other end of the connection.
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1.7.4 Switch Speeds and Forwarding Methods
What action will occur if a host receives a frame with a destination MAC address it does not recognize?
-The host will discard the frame.
-The host sends the frame to the switch to update the MAC address table.
-The host forwards the frame to the router.
-The host forwards the frame to all other hosts.
what is
The host will discard the frame.
7.2 Ethernet MAC Address
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.
what is
The computer has an invalid default gateway address.
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.
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1.8.4 How a Host Routes
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
what is
efficient packet handling
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
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1.8.3 IPv6 Packet
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
what is
neighbor solicitation
&
neighbor advertisement
IPv6 does not use ARP. Instead, ICMPv6 neighbor discovery is used by sending neighbor solicitation and neighbor advertisement messages.
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1.9.3 IPv6 Neighbor Discovery
A Layer 2 switch is used to switch incoming frames from a 1000BASE-T port to a port connected to a 100Base-T network. Which method of memory buffering would work best for this task?
-port-based buffering
-level 1 cache buffering
-shared memory buffering
-fixed configuration buffering
what is
shared memory buffering
With shared memory buffering, the number of frames stored in the buffer is restricted only by the of the entire memory buffer and not limited to a single port buffer. This permits larger frames to be transmitted with fewer dropped frames. This is important to asymmetric switching, which applies to this scenario, where frames are being exchanged between ports of different rates. With port-based memory buffering, frames are stored in queues that are linked to specific incoming and outgoing ports making it possible for a single frame to delay the transmission of all the frames in memory because of a busy destination port. Level 1 cache is memory used in a CPU. Fixed configuration refers to the port arrangement in switch hardware.
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1.7.4 Switch Speeds and Forwarding Methods
What action will occur if a switch receives a frame and does have the source MAC address in the MAC table?
-The switch refreshes the timer on that entry.
-The switch adds it to its MAC address table associated with the port number.
-The switch forwards the frame to the associated port.
-The switch sends the frame to a connected router because the destination MAC address is not local.
what is
The switch refreshes the timer on that entry.
7.2 Ethernet MAC Address
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.
what is
IP relies on upper layer services to handle situations of missing or out-of-order packets.
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.
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1.8.1 Network Layer Characteristics
What IPv4 header field identifies the upper layer protocol carried in the packet?
-Protocol
-Identification
-Version
-Differentiated Services
what is
Protocol
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.
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1.8.2 IPv4 Packet
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
what is
FFFF.FFFF.FFFF
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.
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1.9.2 ARP
What are two examples of the cut-through switching method? (Choose two.)
-store-and-forward switching
-fast-forward switching
-CRC switching
-fragment-free switching
-QOS switching
what is
fast-forward switching
&
fragment-free switching
Store-and forward switching accepts the entire frame and performs error checking using CRC before forwarding the frame. Store-and-forward is often required for QOS analysis. Fast-forward and fragment-free are both variations of the cut-through switching method where only part of the frame is received before the switch begins to forward it.
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1.7.4 Switch Speeds and Forwarding Methods
What action will occur if a host receives a frame with a destination MAC address of FF:FF:FF:FF:FF:FF?
-The host will process the frame.
-The host returns the frame to the switch.
-The host replies to the switch with its own IP address.
-The host forwards the frame to all other hosts.
what is
The host will process the frame.
7.2 Ethernet MAC Address
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
what is
routing packets toward the destination
&
encapsulating PDUs from the transport layer
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.
8.1 Network Layer Characteristics
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.
what is
The TCP/IP stack on the device is working correctly.
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.
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1.8.4 How a Host Routes
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.
what is
They are received and processed by every device on the local network.
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.
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1.9.2 ARP
When the store-and-forward method of switching is in use, what part of the Ethernet frame is used to perform an error check?
cyclic redundancy check (CRC) in the trailer
source MAC address in the header
destination MAC address in the header
protocol type in the header
what is
The cyclic redundancy check (CRC) in the trailer
The cyclic redundancy check (CRC) part of the trailer is used to determine if the frame has been modified during transit. If the integrity of the frame is verified, the frame is forwarded. If the integrity of the frame cannot be verified, then the frame is dropped.
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1.7.4 Switch Speeds and Forwarding Methods
What action will occur if a host receives a frame with a destination MAC address it does not recognize?
-The host will discard the frame.
-The host replies to the switch with its own IP address.
-The host forwards the frame to all other hosts.
-The host returns the frame to the switch.
what is
The host will discard the frame.
7.2 Ethernet MAC Address
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.
what is
The default gateway address is used to forward packets originating from the switch to remote networks.
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.
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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
what is
remote routes
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.
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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.
what is
The frame has the broadcast address as the destination address.
&
The destination address is unknown to the switch.
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.
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1.9.2 ARP