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Intranet is a term used to refer to a private connection of LANs and WANs that belongs
to an organization. An intranet is designed to be accessible only by the organization's
members, employees, or others with authorization.
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Powerline networking adds the ability to connect a device to the network using an
adapter wherever there is an electrical outlet. Uses existing electrical wiring to send
data. It does not replace physical cabling, but can add functionality in places where
wireless access points cannot be used or cannot reach devices.
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Network security includes protecting the confidentiality of data that is on the network. In
this case, because confidential data has been made available to unauthorized users.
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DSL - is always on, high bandwidth, connection that runs over telephone lines.
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CABLE - uses the same coaxial cable that carries television signals into homes to
provide internet access.
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Dialup - telephone is much slower than DSL or cable, but is the least expensive option
for users because it can use any telephone line and a simple modem.
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Satellite - requires a clear line of sight and is affected by trees and other obstructions.
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Criteria for choosing a network medium:
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Distance
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Environment
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Amount of data
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Speed
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Cost of the cable/medium
Video conferencing and voice calls - utilizes real time audio and video communications.
Examples of data traffic that cannot buffer.
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QoS - will ensure an uninterrupted user experience.
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Minimum requirements for home networks - setting up a firewall, antiviruses, etc.
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Passwords - can be used to restrict access to the VTY and console interfaces.
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Layer 2 switch - there is a switch virtual interface (SVI) that provides a means for
remotely managing the device.
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RAM - stores data that is used by the device to support network operations. The running
configuration is stored in RAM. This memory is considered volatile memory because
data is lost during a power cycle.
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Flash Memory - a type of nonvolatile memory that erases data in units called blocks and
rewrites data at the byte level.
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SSH - encrypted
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Telnet - plaintext
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SSH and Telnet - used to connect devices over the network, both are used in-band.
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PuTTY and Terra Term - can be used to make both SSH AND Telnet connections.
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VLANs - a logical overlay network that groups together a subset of devices that share a
physical LAN, isolating the traffic for each group.
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Show ip interface brief - command used to display a brief synopsis of the condition of the
device interfaces.
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Ipconfig command - used to verify TCP/IP properties on a host.
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Ping - command used to verify layer 3 connectivity
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Traceroute command - is used to trace the network path of packets from source to
destination
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Flow control - allows for this by ensuring that data is not sent too fast.
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EIA - organization standard related to electrical wiring, connectors, and the 19 inch racks
used to mount networking equipment.
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IPv4 address - uniquely identifies an end device on the network
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Subnet mask - determines the network address portion and host portion for an IPv4
address
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Default gateway - the ip address of the router interface used for communicating with
hosts in another network.
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DNS server - the IP address of the Domain Name System server.
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DHCP server - not configured manually on end devices. It will be provided by a DHCP
server when an end device requests an IP address.
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Response timeout - if a computer makes a request and does not hear a response within
an amount of time, the computer assumes that no answer is coming and reacts
accordingly.
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HTTP - governs the way that a web server and client interact
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TCP - manages individual conversations between web servers and clients
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IP - is responsible for delivery across the best path to the destination
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Ethernet - takes the packet from IP and formats it for transmission
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MAC address - physical address in the data link layer
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IP address - logical address
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Network protocols - are implemented in hardware, or software, or both. They interact
with each other within different layers of a protocol network.
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Protocol Types
○ Network Communications Protocols - enables one or more devices to
communicate over one or more networks. Examples of protocols include: IP,
Transmission Control Protocol (TCP), HyperText Transfer Protocol (HTTP), and
many more.
○ Network Security Protocols - provides authentication, data integrity, and
encryption. Examples include Secure Shell (SSH), Secure Sockets Layer (SSL),
and Transport Layer Security (TLS).
○ Routing Protocols - enables routers to exchange routing and path information.
Examples include Open Shortest Path First (OSPF) and Border Gateway
Protocol (BGP).
○ Service Discovery Protocols - used for the automatic detection of devices or
services. Examples of service discovery protocols include Dynamic Host
Configuration Protocol (DHCP) which discovers services for IP address
allocation, and Domain Name System (DNS) which is used to perform name-toIP address translation.
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Protocol Functions
○ Addressing - This identifies the sender and the receiver of the message.
Addressing protocols include Ethernet, IPv4, IPv6.
○ Reliability - Provides guaranteed delivery mechanisms in case messages are lost
or corrupted. TCP provides this function.
○ Flow control - maintains an efficient rate of flow of data between two
communicating devices. TCP provides flow control services.
○ Sequencing - Uniquely labels each segment of data. This is useful if the data
segments are lost, delayed or received out-of-order. TCP provides sequencing
services.
○ Error detection - used to detect if data became corrupted during transmission.
○ Application interface - This function contains information used for process-toprocess communications between network applications. For example, when
accessing a web page, HTTP or HTTPS protocols are used to communicate
between the client and server web processes.
Internet Standards
Electronic and Communications Standards
OSI Model Layer
TCP/IP Model Layer
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An IP packet contains:
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○ Source IP address
○ Destination IP address
Bandwidth - capacity of a medium to carry data.
Bandwidth quality is determined by:
● Latency - amount of time for data to travel from one given point to another.
● Throughput - the measure of transfer of bits across the media over a period of
time.
○ Influenced by: amount of traffic, type of traffic, latency caused by
intermediary network devices.
● Goodput - measure of usable data transferred over a period of time.
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Copper cabling:
○ Most common type of cabling
○ Easy to install
○ Inexpensive
○ Limited by distance and signal interference
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Types of copper cabling:
○ Unshielded Twisted-Pair (UTP)
■ Most common
■ Terminated with RJ-45 connectors
■ Consists of 4 pairs of color coded wires
■ Twisted pairs protect from signal interference (EMI, RFI, Crosstalk)
○ Shielded Twisted-Pair (STP)
■ More expensive than UTP
■ Better protection against signal interference using shielding techniques
and special connectors
■ Braided or foil shield
○ Coaxial Cable
■ Copper conductor to transmit signals
■ Plastic insulation
■ Copper braid/Metallic foil shield
■ Attaches antennas to wireless devices
■ Can be bundles with fiber-optic wiring for two-way transmission
■ Terminates with BNC, N type and F type connectors
T568A and T568B Standards
Cable Types and Standards
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IEEE - oversees wireless lan standards
MODULE 4 (canvas)
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An Ethernet mac address consists of 48-bit binary value expressed using 12
hexadecimal values
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Ethernet mac address is 6 bytes in length
All MAC addresses are unique to the ethernet device/interface.
All vendors that sell ethernet devices must register with the IEEE to obtain a unique 6
code identifier called the OUI.
Address Resolution Protocol (ARP) - determines the destination mac address
associated with an IPv6 address known as Neighbor Discovery (ND)
Broadcast MAC address - FF-FF-FF-FF-FF-FF
Ethernet is defined by data link layer and physical layer protocols
Ethernet and the OSI Model
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MAC sublayer - responsible for data encapsulation and accessing media. Provides data
link layer addressing and is integrated with various physical layer technologies.
Examples of this sublayer are 802.3. 802.11, or 802.15
LLC sublayer - communicates between the networking software at the upper layers and
the device hardware at the lower layers. It places information in the frame that identifies
which network layer protocol is being used for the frame. This allows multiple Layer 3
protocols such as IPv4 and IPv6 to use the same network interface and media.
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IEEE 802.3 data encapsulation includes the following:
○ Ethernet frame - This is the internal structure of the Ethernet frame.
○ Ethernet Addressing - 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 Error detection - The Ethernet frame includes a frame check sequence
(FCS) trailer used for error detection.
Ethernet Frame
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Preamble and Start Frame Delimiter Fields
○ The Preamble (7 bytes) and Start Frame Delimiter or SFD (1 byte) fields are
used for synchronization between the sending and receiving devices.
○ These first eight bytes of the frame are used to get the attention of the receiving
nodes.
○ Essentially, the first few bytes tell the receivers to prepare to receive a new
frame.
Destination MAC Address Field
○ This 6-byte field is the identifier for the intended recipient.
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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 addresses in devices until
there is a match.
○ Can be a unicast, multicast, or broadcast address.
Source MAC Address Field
○ Identifies the originating NIC or interface of the frame.
Type / Length
○ Identifies the upper layer protocol encapsulated in the Ethernet frame.
○ Common values are in hexadecimal, 0x800 for IPv4, 0x86DD for IPv6 and 0x806
for ARP
○ You may also see this field referred to as EtherType.
Data Field
○ This field contains the encapsulated data from a higher layer, which is a generic
IPv4 packet.
○ All frames must be at least 64 bytes long.
○ If a small packet is encapsulated, additional bits called a pad are used to
increase the size of the frame to this minimum size.
Frame CHeck Sequence
○ The FCS field 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.
IPv4 addresses - represented in decimal and binary
IPv6 addresses - represented in hexadecimal
Ethernet MAC address
○ is a 48-bit address expressed using 12 hexadecimal digits.
○ All vendors that sell Ethernet devices must register with the IEEE to obtain a
unique 6 hexadecimal code called the Organizationally Unique Identifier (OUI)
○ A mac address must:
■ Use its assigned OUI as the first 6 hexadecimal digits
■ Assign a unique value in the last 6 hexadecimal digits
Ethernet MAC address
Types of switching
Variants of cut-through switching:
Memory buffering methods
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Two of the most basic settings on a switch
○ bandwidth/speed
○ Duplex
■ Duplex and bandwidth settings should match between devices
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Full duplex - both ends of the connection can send and receive simultaneously
Half duplex - only one end of the connection can send at a time
Example of duplex mismatch
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Auto-MDIX - a feature that detects ethernet cable type
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Minimum and Maximum size of an ethernet frame
○ 1518 bytes (Maximum)
○ 64 bytes (Minimum)
Network Layer Protocols
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Addressing end devices
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○ 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.
○ Adds IP header information
■ Source address
■ Destination address
○ Process performed by the source of the IP packet
Routing
○ Service to direct the packets to a destination host on another network.
○ To travel to other networks, the packet must be processed by a router.
○ A packet may cross many routers before reaching the destination
○ Each router crossed before reaching the destination is called a “hop”
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.
After the packet is de-encapsulated by the network layer, the resulting Layer 4
PDU is passed up to the appropriate service at the transport layer. The deencapsulation process is performed by the destination host of the IP packet.\
Basic characteristics of IP:
Fields in the IPv4 packet header
Limitations of IPv4
Improvements of IPv6
Fields that determine packet lifespan
● IPv4
○ Time To Live (TTL)
● IPv6
○ Hop Limit
● Both are the same, but use different names. The TTL/Hop Limit is reduced by one for
each time a packet traverses a layer 3 device (switch or router)
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IPv4 and IPv6 address space comparison
○ IPv4 - 4 billion addresses
○
IPv6 - 340 undecillion addresses
IPv6 packet header
A host can send packets to:
Whether a packet is destined for a local host or a remote host is determined by the source end
device. The source end device determines whether the destination IP address is on the same
network that the source device itself is on. The method of determination varies by IP version:
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Default gateway - is the network device (router or layer 3 switch) that can route traffic to
other networks. If a network is a room, the default gateway is a door.
A router can learn about remote networks in one of two ways:
● Manually (Static routing) - remote networks are manually entered into the route table
using static routes.
○ Route entries that are manually configured
○ The static route includes the remote network address and the IP address of the
next hop router.
○ If there is a change in the network topology, the static route is not automatically
updated and must be manually reconfigured.
○ Static routes are appropriate for small networks with few or no redundant links.
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Dynamically (Dynamic routing) - automatically learned using a dynamic routing protocol
○ Automatically share routing information with other routers
○ Compensates for any changes in the network topology.
○ Protocols include OSPF, and Enhanced Interior Gateway Routing Protocol
(EIGRP).
○ More
Routing table acronyms via Show IP route:
1.
2.
3.
4.
5.
6.
7.
8.
9.
LLC - Logical Link Control
MAC - Media Access Control
IP - Internet Protocol
OSI - Open Systems Interconnection
FCS - Frame Check Sequence
ARP - Address Resolution Protocol
PDU - Protocol Data Unit
TCP - Transmission Control Protocol
SLAAC - Stateless Address Auto-Configuration
10. AUTO-MDIX - Media Dependent Interface
11. MTU - Maximum Transmission Unit
12. CSMA/CD - Carrier Sense Multiple Access/Collision Detection
13. CRC - Cyclic Redundancy Check
14. OUI - Organizationally Unique Identifier
15. TTL - Time To Live
16. CAM - Content Addressable Memory