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53 Cards in this Set

  • Front
  • Back
What layers of the OSI model does Ethernet operate?
data link layer

physical layer
LLC sublayer
handles the communication between the upper layers and the lower layers. This is typically between the networking software and the device hardware.
What does the LLC sublayer do to the network protocol data which is typically an IPv4 packet?
adds control information to help deliver the packet to the destination node
MAC sublayer
MAC is implemented by hardware, typically in the computer NIC.
Data encapsulation
The data encapsulation process includes frame assembly before transmission, and frame disassembly upon reception of a frame. In forming the frame, the MAC layer adds a header and trailer to the network layer PDU.
Data encapsulation provides three primary functions
Frame delimiting


Error detection
Frame delimiting
The framing process provides important delimiters that are used to identify a group of bits that make up a frame. This process provides synchronization between the transmitting and receiving nodes.
The encapsulation process also provides for data link layer addressing. Each Ethernet header added in the frame contains the physical address (MAC address) that enables a frame to be delivered to a destination node.
Error detection
Each Ethernet frame contains a trailer with a cyclic redundancy check (CRC) of the frame contents. After reception of a frame, the receiving node creates a CRC to compare to the one in the frame. If these two CRC calculations match, the frame can be trusted to have been received without error.
Media Access Control
The second responsibility of the MAC sublayer is media access control. Media access control is responsible for the placement of frames on the media and the removal of frames from the media. MAC communicates directly with the physical layer.
CSMA/Collision Detection (CSMA/CD)
the device monitors the media for the presence of a data signal. If a data signal is absent, indicating that the media is free, the device transmits the data. If signals are then detected that show another device was transmitting at the same time, all devices stop sending and try again later.
CSMA/Collision Avoidance (CSMA/CA)
the device examines the media for the presence of a data signal. If the media is free, the device sends a notification across the media of its intent to use it. The device then sends the data. This method is used by 802.11 wireless networking technologies.
The primary fields in the Ethernet frame are?
Preamble and Start Frame Delimiter Fields
Destination MAC Address Field
Source MAC Address Field
Length Field
Data Field
Frame Check Sequence Field
Preamble and Start Frame Delimiter Fields
The Preamble (7 bytes) and Start Frame Delimiter (SFD), also called the Start of Frame (1 byte), fields are used for synchronization between the sending and receiving devices
Destination MAC Address Field
This 6-byte field is the identifier for the intended recipient. This address is used by Layer 2 to assist devices in determining if a frame is addressed to them. The address in the frame is compared to the MAC address in the device. If there is a match, the device accepts the frame.
Source MAC Address Field
This 6-byte field identifies the frame's originating NIC or interface.
Length Field
This is used later as part of the FCS to ensure that the message was received properly. Otherwise the purpose of the field is to describe which higher-layer protocol is present.
Data Field
This field (46 - 1500 bytes) contains the encapsulated data from a higher layer, which is a generic Layer 3 PDU, or more commonly, an IPv4 packet.
Frame Check Sequence Field
The Frame Check Sequence (FCS) field (4 bytes) is used to detect errors in a frame. It uses a cyclic redundancy check (CRC). The sending device includes the results of a CRC in the FCS field of the frame. The receiving device receives the frame and generates a CRC to look for errors.
Fast-forward switching
offers the lowest level of latency. Fast-forward switching immediately forwards a packet after reading the destination address
Fragment-free switching
the switch stores the first 64 bytes of the frame before forwarding. Fragment-free switching can be viewed as a compromise between store-and-forward switching and fast-forward switching.
Port-based Memory Buffering
in port based memory buffering, frames are stored in queues that are linked to specific incoming and outgoing ports.
Shared memory
shared memory buffering deposits all frames into a common memory buffer, which all the ports on the switch share.
Fixed Configuration Switches
Fixed configuration switches are just as you might expect, fixed in their configuration. What that means is that you cannot add features or options to the switch beyond those that originally came with the switch.
Modular Switches
Modular switches offer more flexibility in their configuration. Modular switches typically come with different sized chassis that allow for the installation of different numbers of modular line cards.
Switch Virtual Interface (SVI)
Logical interface on a switch associated with a virtual local area network (VLAN)
Routed Port
Physical port on a Layer 3 switch configured to act as a router port.
Layer 3 Ether Channel
Logical interface on a Cisco device associated with a bundle of routed ports.
Which destination address is used in an ARP request frame?
What sub layer is responsible for communicating directly with the physical layer.
What is a characteristic of a contention-based access method?
It is a nondeterministic method.
A collision fragment, with less than 64 bytes in the frame
runt frame
Which two functions or operations are performed by the MAC sublayer?
It is responsible for Media Access Control.

It adds a header and trailer to form an OSI Layer 2 PDU.
What type of address is 01-00-5E-0A-00-02?
a MAC address that reaches a specific group of hosts.

The multicast MAC address is a special value that begins with 01-00-5E in hexadecimal. It allows a source device to send a packet to a group of devices.
Which interface command must be entered in a Layer 3 switch before an IPv4 address can be assigned to that interface?
no switchport
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. When a Layer 2 switch receives a frame with a broadcast destination address, it floods the frame to all ports except the port on which it received the frame.
Which term defines the processing capabilities of a switch by rating how much data can be processed per second?
forwarding rate
What is a characteristic of a contention-based access method?
It is a nondeterministic method.
What describes features or functions of the logical link control sublayer in Ethernet standards?

Logical link control is implemented in software.
What is the purpose of the preamble in an Ethernet frame?
is used for timing synchronization
What describes a fixed configuration Ethernet switch?
The number of ports on the switch cannot be increased.

A fixed configuration switch may be stackable.
Which two statements are correct about MAC and IP addresses during data transmission if NAT is not involved
Destination IP addresses in a packet header remain constant along the entire path to a target host

Destination and source MAC addresses have local significance and change every time a frame goes from one LAN to another
What is the Layer 2 multicast MAC address that corresponds to the Layer 3 IPv4 multicast address
The multicast MAC address is a special value that begins with 01-00-5E in hexadecimal. The value ends by converting the lower 23 bits of the IP multicast group address into the remaining 6 hexadecimal characters of the Ethernet address. The remaining bit in the MAC address is always a "0".
A host is trying to send a packet to a device on a remote LAN segment, but there are currently no mappings in its ARP cache. How will the device obtain a destination MAC address?
It will send an ARP request for the MAC address of the default gateway.
What are two features of ARP?
If a device receiving an ARP request has the destination IPv4 address, it responds with an ARP reply. If a host is ready to send a packet to a local destination device and it has the IP address but not the MAC address of the destination, it generates an ARP broadcast.
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?
shared memory buffering
When would a switch record multiple entries for a single switch port in its MAC address table?
when another switch is connected to the switch port
A network administrator is connecting two modern switches using a straight-through cable. The switches are new and have never been configured. Which three statements are correct about the final result of the connection?
The link between the switches will work at the fastest speed that is supported by both switches. The auto-MDIX feature will configure the interfaces eliminating the need for a crossover cable. The link between switches will work as full-duplex.
How does adding an Ethernet line card affect the form factor of a switch?
by expanding the port density
Which address or combination of addresses does a Layer 3 switch use to make forwarding decisions?
MAC and IP addresses
What statement illustrates a drawback of the CSMA/CD access method?
collisions can decrease network performance.
The binary number 0000 1010 can be expressed as what in hexadecimal?