CCNA 1 - Module 5-7 Flashcards
Binary vs. Decimal Numbering System
- Binary numbering system consists of 1s and 0s, called bits
- Decimal numbering system consists of digits 0 through 9
a digit represents different values depending on the “position” the digit occupies in the sequence of numbers.
Binary Positional Notation
- s a base sixteen numbering system, using the digits 0 through 9 and letters A to F.
- It is easier to express a value as a single hexadecimal digit than as four binary bit.
Hexadecimal
- are 128 bits in length. Every 4 bits is represented by a single hexadecimal digit. That makes the IPv6 address a total of 32 hexadecimal values.
IPv6 addresses
How to convert hexadecimal numbers to decimal values
- Convert the hexadecimal number to 4-bit binary strings.
- Create 8-bit binary grouping starting from the rightmost position.
- Convert each 8-bit binary grouping into their equivalent decimal digit.
How to convert decimal numbers to hexadecimal numbers
- Convert the decimal number to 8-bit binary strings.
- Divide the binary strings in groups of four starting from the rightmost position.
- Convert each four binary numbers into their equivalent hexadecimal digit.
- is responsible for communications between end-device network interface cards.
- It allows upper layer protocols to access the physical layer media and encapsulates Layer 3 packets (IPv4 and IPv6) into Layer 2 Frames.
- It also performs error detection and rejects corrupts frames.
Data Link layer
- The ___________ communicates between the networking software at the upper layers and the device hardware at the lower layers.
LLC sublayer
- The _______ is responsible for data encapsulation and media access control.
MAC sublayer
is the arrangement and relationship of the network devices and the interconnections between them.
topology of a network
- – shows physical connections and how devices are interconnected.
Physical topology
- – identifies the virtual connections between devices using device interfaces and IP addressing schemes
Logical topology
- – the simplest and most common WAN topology. Consists of a permanent link between two endpoints.
Point-to-point
- – similar to a star topology where a central site interconnects branch sites through point-to-point links
Hub and spoke
- – provides high availability but requires every end system to be connected to every other end system
Mesh
bus vs. ring
- Bus – All end systems chained together and terminated on each end.
- Ring – Each end system is connected to its respective neighbors to form a ring
- Only allows one device to send or receive at a time on a shared medium.
- Used on WLANs and legacy bus topologies with Ethernet hubs.
Half-duplex communication
- Allows both devices to simultaneously transmit and receive on a shared medium.
- Ethernet switches operate in full-duplex mode.
Full-duplex communication
- All nodes operating in half-duplex, competing for use of the medium. Examples are:
- Carrier sense multiple access with collision detection (CSMA/CD) as used on legacy bus-topology Ethernet.
- Carrier sense multiple access with collision avoidance (CSMA/CA) as used on Wireless LANs
Contention-based access
- Deterministic access where each node has its own time on the medium.
- Used on legacy networks such as Token Ring and ARCNET.
Controlled access
- Used by legacy Ethernet LANs.
- Operates in half-duplex mode where only one device sends or receives at a time.
- Uses a collision detection process to govern when a device can send and what happens if multiple devices send at the same time
CSMA/CD
- Used by IEEE 802.11 WLANs.
- Operates in half-duplex mode where only one device sends or receives at a time.
- Uses a collision avoidance process to govern when a device can send and what happens if multiple devices send at the same time.
CSMA/CA
Address is also called __________
Physical address
: (IEEE 802.2) Places information in the frame to identify which network layer protocol is used for the frame.
LLC Sublayer
: (IEEE 802.3, 802.11, or 802.15) Responsible for data encapsulation and media access control, and provides data link layer addressing.
MAC Sublayer
- This is the internal structure of the Ethernet frame.
- a. 64 bytes < Ethernet Frame Size < 1518 bytes
- b. 64 bytes > EFS == ‘collision fragment’ or ‘runt frame’ => automatically discarded
- c. 1500 bytes < EFS == ‘jumbo’ or ‘baby giant frame’
Ethernet frame
- The Ethernet frame includes both a source and destination MAC address to deliver the Ethernet frame from Ethernet NIC to Ethernet NIC on the same LAN.
Ethernet Addressing
- The Ethernet frame includes a frame check sequence (FCS) trailer used for error detection
Ethernet Error detection
is received and processed by every device on the Ethernet LAN.
Ethernet broadcast frame
is received and processed by a group of devices that belong to the same multicast group.
Ethernet multicast frame
- This frame forwarding method receives the entire frame and computes the CRC. If the CRC is valid, the switch looks up the destination address, which determines the outgoing interface. Then the frame is forwarded out of the correct port.
Store-and-forward switching
- This frame forwarding method forwards the frame before it is entirely received. At a minimum, the destination address of the frame must be read before the frame can be forwarded
Cut-through switching
- Provides the lowest latency by forwarding packets immediately after reading the destination address.
- May relay packets with errors since it starts forwarding before the entire packet is received; faulty packets are discarded by the destination NIC.
- Represents a typical cut-through switching method.
Fast-forward switching
- Balances the high latency and integrity of store-and-forward switching with the low latency and reduced integrity of fast-forward switching.
- Stores and checks the first 64 bytes of a frame for errors before forwarding, helping to detect collisions that typically occur in that segment.
Fragment-free switching
- Frames are stored in queues that are linked to specific incoming and outgoing ports.
- A frame is transmitted to the outgoing port only when all the frames ahead in the queue have been successfully transmitted. It is possible for a single frame to delay the transmission of all the frames in memory because of a busy destination port.
- This delay occurs even if the other frames could be transmitted to open destination ports.
Port-based memory
- Deposits all frames into a common memory buffer shared by all switch ports and the amount of buffer memory required by a port is dynamically allocated.
- The frames in the buffer are dynamically linked to the destination port enabling a packet to be received on one port and then transmitted on another port, without moving it to a different queue.
- Shared memory buffering also results in larger frames that can be transmitted with fewer dropped frames. This is important with asymmetric switching which allows for different data rates on different ports. Therefore, more bandwidth can be dedicated to certain ports (e.g., server port).
Shared memory
full-duplex vs. half-duplex
-
Full-duplex - Both ends of the connection can send and receive simultaneously.
o Gigabit Ethernet ports only operate in full-duplex. - **Half-duplex **- Only one end of the connection can send at a time.
__________ feature is enabled by default on switches running Cisco IOS Release 12.2(18)SE or later. However, the feature could be disabled. For this reason, you should always use the correct cable type and not rely on the auto-MDIX feature
* can be re-enabled using the mdix auto interface configuration command
auto-MDIX
