Transcript Repeaters and Hubs

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Chapter 6
Network Hardware, Switching, and Routing
 Identify
the functions of LAN connectivity hardware
 Install, configure, and differentiate between
network devices such as NICs, hubs, bridges,
switches, routers, and gateways
 Explain the advanced features of a switch and
understand popular switching techniques,
including VLAN management
 Explain the purposes and properties of routing
 Describe common IPv4 and IPv6 routing protocols
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 Connectivity
devices
o Enable device transmission
o Transceiver
• Transmits and receives data
 Physical
layer and Data Link layer functions
o Issue data signals
o Assemble and disassemble data frames
o Interpret physical addressing information
o Determine right to transmit data
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 Smart
hardware
o Prioritization
o Network management
o Buffering
o Traffic-filtering
 Do
not analyze information
o Added by Layers 3 through 7 OSI model protocols
 Importance
o Common to every networking device, network
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
Expansion slots
o Multiple electrical contacts on motherboard
o Allow bus expansion
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Expansion card (expansion board)
o Circuit board for additional devices
o Inserts into expansion slot, establishes electrical connection
o Device connects to computer’s main circuit or bus
o Computer centrally controls device
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 Multiple
bus types
o PCIe bus: most popular expansion board NIC
 PCIe
(Peripheral Component Interconnect Express)
o 32-bit bus
o Maximum data transfer rate: 1 Gbps
o Introduced in 2004
Figure 6-1 PCIe expansion board NIC
Courtesy of Intel Corporation
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On-Board NICs
o Connect device directly to motherboard
o On-board ports: mouse, keyboard
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New computers, laptops
o Use onboard NICs integrated into motherboard
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Advantages
o Saves space
o Frees expansion slots
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Figure 6-3 Motherboard with on-board NICs
Courtesy of EVGA USA
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 Installing
NIC hardware
o Read manufacturer’s documentation
 Install
expansion card NIC
o Gather needed tools
o Unplug computer, peripherals, and network cable
o Ground yourself
o Open computer case
• Select slot, insert NIC, attach bracket, verify cables
o Replace cover, turn on computer
• Configure NIC software
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Figure 6-4 A properly inserted expansion board NIC
Courtesy of Gary Herrington Photography
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 Repeaters
o Operate in Physical OSI model layer
o No means to interpret data
o Regenerate signal
 Hub
o Repeater with more than one output port
o Typically contains multiple data ports
• Patch cables connect printers, servers, and workstations
o Most contain uplink port
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 Connectivity
devices that subdivide a network
o Segments
 Traditional
switches
o Operate at Data Link OSI model layer
 Modern
switches
o Can operate at Layer 3 or Layer 4
 Switches
interpret MAC address information
 Common switch components
o Internal processor, operating system, memory, ports
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 Follow
manufacturer’s guidelines
 General steps (assume Cat 5 or better UTP)
o Verify switch placement
o Turn on switch
o Verify lights, self power tests
o Configure (if necessary)
o Connect NIC to a switch port (repeat for all nodes)
o After all nodes connected, turn on nodes
o Connect switch to larger network (optional)
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Figure 6-13 A switch on a small network
Courtesy Course Technology/Cengage Learning
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 Difference
in switches
o Incoming frames interpretation
o Frame forwarding decisions making
 Four
switching modes exist
o Two basic methods discussed
• Cut-through mode
• Store-and-forward mode
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 Cut-through
mode
o Switch reads frame’s header
o Forwarding decision made before receiving entire packet
• Uses frame header: first 14 bytes contains destination MAC
address
o Cannot verify data integrity using frame check sequence
o Can detect erroneously shortened packets (runts)
o Runt detected: wait for integrity check
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 Cut-through
mode (cont’d.)
o Cannot detect corrupt packets
o Advantage: speed
o Disadvantage
• Data buffering (switch flooded with traffic)
o Best use
• Small workgroups needing speed
• Low number of devices
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 Store-and-forward
mode
o Switch reads entire data frame into memory
o Checks for accuracy before transmitting information
o Transmit data more accurately than cut-through mode
o Slower than cut-through mode
o Best uses
• Larger LAN environments; mixed environments
o Can transfer data between segments running different
transmission speeds
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 VLANs
(virtual local area networks)
o Logically separate networks within networks
• Groups ports into broadcast domain
 Broadcast
domain
o Port combination making a Layer 2 segment
o Ports rely on Layer 2 device to forward broadcast frames
 Collision
domain
o Ports in same broadcast domain
• Do not share single channel
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 Advantage
of VLANs
o Flexible
• Ports from multiple switches or segments
• Use any end node type
o Reasons for using VLAN
• Separating user groups
• Isolating connections
• Identifying priority device groups
• Grouping legacy protocol devices
• Separating large network into smaller subnets
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
Switch typically preconfigured
o One default VLAN
o Cannot be deleted or renamed
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Create additional VLANs
o Indicate to which VLAN each port belongs
o Additional specifications
• Security parameters, filtering instructions, port performance
requirements, network addressing and management options
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Maintain VLAN using switch software
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
Potential problem
o Cutting off group from rest of network
• Correct by using router or Layer 3 switch
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Trunking
o Switch’s interface carries traffic of multiple VLANs
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Trunk
o Single physical connection between switches
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VLAN data separation
o Frame contains VLAN identifier in header
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IEEE standard 802.1D
Operates in Data Link layer
Prevents traffic loops
o Calculating paths avoiding potential loops
o Artificially blocking links completing loop
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Three steps
o Select root bridge based on Bridge ID
o Examine possible paths between network bridge and root bridge
o Disables links not part of shortest path
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Figure 6-17 Enterprise-wide switched network
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
Layer 3 switch (routing switch)
o Interprets Layer 3 data
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Layer 4 switch
o Interprets Layer 4 data
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Content switch (application switch)
o Interprets Layer 4 through Layer 7 data
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Advantages
o Advanced filtering
o Keeping statistics
o Security functions
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
Multiport connectivity device
o Directs data between network nodes
o Integrates LANs and WANs
• Different transmission speeds, protocols
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Operate at Network layer (Layer 3)
o Directs data from one segment or network to another
o Logical addressing
o Protocol dependent
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Slower than switches and bridges
o Need to interpret Layers 3 and higher information
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 Intelligence
o Tracks node location
o Determine shortest, fastest path between two nodes
o Connects dissimilar network types
 Large
LANs and WANs
o Routers indispensable
 Router
components
o Internal processor, operating system, memory, input and
output jacks, management control interface
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Figure 6-19 Routers
Courtesy Course Technology/Cengage Learning
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Router capabilities
o Connect dissimilar networks
o Interpret Layer 3 addressing
o Determine best data path
o Reroute traffic
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Optional router functions
o Filter broadcast transmissions
o Enable custom segregation, security
o Support simultaneous connectivity
o Provide fault tolerance
o Monitor network traffic
o Diagnose problems and trigger alarms
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
Interior router
o Directs data between nodes on a LAN
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Exterior router
o Directs data between nodes external to a LAN
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Border routers
o Connect autonomous LAN with a WAN
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Routing tables
o Identify which routers serve which hosts
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 Static
routing
o Router configured to use specific path between nodes
 Dynamic
routing
o Automatically calculates best path between nodes
 Installation
o Simple for small office or home office LANs
• Web-based configuration
o Challenging for sizable networks
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 Best
path
o Most efficient route from one node to another
o Dependent on:
• Hops between nodes
• Current network activity
• Unavailable link
• Network transmission speed
• Topology
o Determined by routing protocol
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 Routing
metric factors
o Number of hops
o Throughput on potential path
o Delay on a potential path
o Load (traffic)
o Maximum transmission unit (MTU)
o Cost
o Reliability of potential path
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
Distance-vector routing protocols
o Determine best route based on distance to destination
o Factors
• Hops, latency, network traffic conditions
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RIP (Routing Information Protocol)
o Only factors in number of hops between nodes
• Limits 15 hops
o Type of IGP (Interior Gateway Protocol)
• Can only route within internal network
o Slower and less secure than other routing protocols
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 RIPv2
(Routing Information Protocol Version 2)
o Generates less broadcast traffic, more secure
o Cannot exceed 15 hops
o Less commonly used
 BGP
(Border Gateway Protocol)
o Communicates using BGP-specific messages
o Many factors determine best paths
o Configurable to follow policies
o Type of EGP (Exterior Gateway Protocol)
o Most complex (choice for Internet traffic)
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 Link-state
routing protocol
o Routers share information
• Each router independently maps network, determines best path
 OSPF
(Open Shortest Path First)
o Interior or border router use
o No hop limit
o Complex algorithm for determining best paths
o Each OSPF router
• Maintains database containing other routers’ links
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 Hybrid
o Link-state and distance-vector characteristics
o EIGRP (Enhanced Interior Gateway Routing Protocol)
• Most popular
• Cisco network routers only
o EIGRP benefits
• Fast convergence time, low network overhead
• Easier to configure and less CPU-intensive than OSPF
• Supports multiple protocols
• Accommodates very large, heterogeneous networks
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Table 6-1 Summary of common routing protocols
Courtesy Course Technology/Cengage Learning
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
Network adapter types vary
o Access method, transmission speed, connector interfaces, number
of ports, manufacturer, device type

Repeaters
o Regenerate digital signal


Bridges can interpret the data they retransmit
Switches subdivide a network
o Generally secure
o Create VLANs

Various routing protocols exist
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