CCNA Exploration
Network Fundamentals
Chapter 10
Planning and Cabling Networks
Copyright © 2008
Version 4.0
Ch 10 - 1
Routers
• Primary devices used to interconnect networks
– each port on a router connects to a different network and routes packets
between networks
• Have the ability to
break up broadcast
domains (BD) and
collision domains
(CD)
• Used to interconnect
networks that use
different
technologies
hub
switch
switch
router
router
– LAN and WAN
interfaces
Copyright © 2008
Version 4.0
Ch 10 - 2
Hubs
• A hub receives a signal, regenerates it, and sends the signal over all
ports
– ports use a shared bandwidth approach
– reduces the LAN performance due to collisions and recovery
– maintains a single collision domain
• Used in a small LAN that requires low
throughput requirements or when
finances are limited
• Less expensive than a switch
Copyright © 2008
Version 4.0
Ch 10 - 3
Switches
• A switch receives a frame and regenerates each bit of the frame on
to the appropriate destination port
• Used to segment a network into multiple collision domains
• Each port on the switch creates a
separate collision domain
– creates a point-to-point logical topology
to the device on each port
– provides dedicated bandwidth on each
port
• Can be used to interconnect network
segments of different speeds
Copyright © 2008
Version 4.0
Ch 10 - 4
Device Selection Factors
•
•
•
•
•
Cost
Speed and types of ports/interfaces
Expandability
Manageability
Additional features and services
Copyright © 2008
Version 4.0
Ch 10 - 5
Factors to Consider in Choosing a Switch
• Cost
– its capacity and features
– network management capabilities, embedded security technologies and
optional advanced switching technologies
• Simple “cost per port” calculation
– deploy one large switch at a central location
– cost savings may be offset
by the expense from the
longer cables
• Compare the cost of
deploying a number of
smaller switches connected
by a few long cables to a
central switch
Copyright © 2008
Version 4.0
Ch 10 - 6
Factors to Consider in Choosing a Switch
(cont’d)
• Investing in redundancy
– a secondary switch to operate concurrently with the primary central
switch
– additional cabling to allow the physical network to continue its operation
even if one device fails
Copyright © 2008
Version 4.0
Ch 10 - 7
Speed and Type of Ports (Interfaces)
• Purchasing decisions
– just enough ports for today’s needs
– mixture of UTP speeds
– both UTP and fiber ports
Copyright © 2008
Version 4.0
Ch 10 - 8
Factors to Consider in Choosing a Router
• Expandability
– modular devices have expansion slots that provide the flexibility to add
new modules as requirement evolve
– basic number of fixed ports as well as expansion slots
• Media
– additional modules for fiber optics can increase the cost
• Operating system features
– different versions of the operating system support certain features and
services
– security, quality of service, voice over IP, routing multiple Layer 3
protocols, NAT and DHCP
Copyright © 2008
Version 4.0
Ch 10 - 9
LAN Cabling Areas
•
•
•
•
Work area
Telecommunication room, also known as distribution facility
Backbone cabling, also known as vertical cabling
Distribution cabling, also known as horizontal cabling
Copyright © 2008
Version 4.0
Ch 10 - 10
LAN Cabling Areas (cont’d)
• Cable length
–
–
–
–
ANSI/TIA/EIA-568-B standard for UTP installations
maximum distance of 100 meters per channel
up to 5 meters of patch cable for interconnecting patch panels
up to 5 meters of patch cable from the cable termination point on the
wall to the computer and telephone
• Work area
– end user devices are located
– minimum of two jacks
– patch cables, which are straight-through UTP cables, are used to
connect end user devices to the wall jacks
– EIA/TIA standard specifies the UTP patch cords to connect devices to
the wall jacks have a maximum length of 10 meters
– a crossover cable is used to connect a switch or hub to the wall jack
Copyright © 2008
Version 4.0
Ch 10 - 11
LAN Cabling Areas (cont’d)
• Telecommunications room
– contains the intermediary devices – hubs, switches, routers and data
service units (DSUs)
– where connections to intermediary devices take place
– these devices provide the transitions between the vertical (or backbone)
cabling and the horizontal cabling
– patch cords are used to connect patch panels and intermediary devices
– servers are also housed in the telecommunication room
• Horizontal cabling
– refers to cables connecting the telecommunication rooms with the work
areas
– maximum cable length from a termination point in the
telecommunication room to the termination at the work area outlet must
not exceed 90 meters
Copyright © 2008
Version 4.0
Ch 10 - 12
LAN Cabling Areas (cont’d)
• Vertical cabling
– refers to the cabling used to connect the telecommunication rooms to
the equipment rooms
– also interconnects multiple telecommunication rooms throughout the
facility
– used for aggregated traffic, such as traffic to and from the Internet
access to corporate resources at a remote location
– typically require high bandwidth media such as fiber-optic cabling
Copyright © 2008
Version 4.0
Ch 10 - 13
Types of Media
• UTP (Category 5, 5e, 6 and 7)
• Fiber optics
• Wireless
Copyright © 2008
Version 4.0
Ch 10 - 14
Choosing a Media
• Cable length
– does the cable need to span across a room or from a building to a
building?
• Cost
– does the budget allow for using a more expensive media type?
• Bandwidth
– does the technology used with the media provide adequate bandwidth?
• Ease of installation
– does the implementation team have the ability to install the cable or is
vendor required?
• Susceptible to EMI/RFI
– is the local environment going to interfere with the signal?
Copyright © 2008
Version 4.0
Ch 10 - 15
Cable Length
• Total length of cable
– all cables from the end devices in the work area to the intermediary
device, usually a switch, in the telecommunication room
– cable from the devices to the wall plug, through the building from the
wall plug to the cross-connect (or patch panel) and from the patch panel
to the switch
• Signal attenuation and
exposure to possible
interference increase with
cable length
– the horizontal cabling length
for UTP needs to stay within
the recommended
maximum distance of 90
meters
Copyright © 2008
Version 4.0
Ch 10 - 16
Ethernet Cabling Standards
Ethernet Type
Bandwidth
Cable Type
Maximum Distance
10Base-T
10Mbps
Cat 3/Cat 5 UTP
100m
100Base-TX
100Mbps
Cat 5 UTP
100m
100Base-TX
200Mbps
Cat 5 UTP
100m
100Base-FX
100Mbps
Multi-mode fiber
400m
100Base-FX
200Mbps
Multi-mode fiber
2Km
1000Base-T
1Gbps
Cat 5e UTP
100m
1000Base-TX
1Gbps
Cat 6 UTP
100m
1000Base-SX
1Gbps
Multi-mode fiber
550m
1000Base-LX
1Gbps
Single-mode fiber
2Km
10GBase-T
10Gbps
Cat 6a/Cat 7 UTP
100m
10GBase-LX
10Gbps
Multi-mode fiber
100m
10GBase-LX
10Gbp
Single-mode fiber
10Km
Copyright © 2008
Version 4.0
Ch 10 - 17
Cable Cost and Bandwidth
• Cost
–
–
–
–
depend on media type such as copper or fiber optic
budget for fiber-optic cabling
installation costs for fiber are significantly higher
match the performance needs of the users with the cost of the
equipment and cabling to achieve the best cost/performance ratio
• Bandwidth
– devices in a network have different bandwidth requirements
– select a media that will provide high bandwidth, and can grow to meet
increased bandwidth requirements and newer technologies
Copyright © 2008
Version 4.0
Ch 10 - 18
Cable Installation
• Ease of cable installation varies according to
cable types and building architecture
– access to floor or roof spaces
– physical size and properties of the cable
• Cables are usually installed in raceways
– a raceway is an enclosure or tube that
encloses and protects the cable
• UTP cable is relatively lightweight and
flexible and has a small diameter
– can fit into small spaces
• Fiber-optic cables contain a thin glass fiber
– crimps or sharp bends can break the fiber
• Wireless networks require less cabling
Copyright © 2008
Version 4.0
Ch 10 - 19
Types of Interference
• Electromagnetic interference (EMI)
– undesirable disturbance that affects an electric circuit due to
electromagnetic radiation emitted from an external source such as
electrical machines and lighting
• Radio frequency interference (RFI)
– radio frequency signals transmitted from nearby radio stations
that interfere with the operating frequency of the equipment
• Wireless is the medium most susceptible to RFI
– potential sources of interference must be identified
Copyright © 2008
Version 4.0
Ch 10 - 20
UTP Cabling Connections
• Specified by the Electronics Industry Alliance/Telecommunications
Industry Association (EIA/TIA)
Copyright © 2008
Version 4.0
Ch 10 - 21
Types of Interfaces
• Media-dependent interface (MDI)
– pins 1 and 2 are used for transmitting
– pins 3 and 6 are used for receiving
– devices such as computers, servers or routers have MDI connections
• Media-dependent interface, crossover (MDIX)
– devices that provide LAN connectivity such as hubs or switches use
MDIX connections
– MDIX connections swap the transmit-receive pairs internally
– end devices connect to hubs or switches using straight-through cables
Copyright © 2008
Version 4.0
Ch 10 - 22
Straight-Through UTP Cables
• A straight-through cable has the
same termination at each
connector end
– in accordance with either the
T568A or T568B standards
• Use the same color codes
throughout the LAN for
consistency in documentation
• Used for connecting different
types of devices
– switch to router Ethernet port
– computer to switch
– computer to hub
Copyright © 2008
Version 4.0
Ch 10 - 23
Cross-over UTP Cables
• A cross-over cable has T568A
termination at one end and a
T568B termination at the other
end
– transmit pins at each end connect
to the receive pins at the other
end
• Used for connecting same types
of devices
–
–
–
–
–
switch to switch
switch to hub
computer to router Ethernet port
router to router Ethernet port
computer to computer
Copyright © 2008
Version 4.0
Ch 10 - 24
LAN Connections
• Straight-through UTP cables are used for connecting different types
of devices, such as a router LAN interface to a switch
• Cross-over UTP cables provide connections between same type of
devices, such as a switch to another switch
Copyright © 2008
Version 4.0
Ch 10 - 25
MDI/MDIX Selection
• On some devices, ports may have a mechanism that electrically
swaps the transmit and receive pairs
– engage the mechanism to change the port setting
• Some devices allow for selecting whether a port functions as MDI or
MDIX during configuration
• Many newer devices have an automatic crossover feature
– device detects the required cable type and configures the interface
– auto-detection can be enabled by default or via configuration command
Copyright © 2008
Version 4.0
Ch 10 - 26
WAN Connections
• WAN links span extremely long distances
– over wide geographic areas
• The chart shows some examples of WAN connections
– telephone line RJ-11 connectors for dial-up or DSL connection
– coaxial cable F connector for cable connection
– serial connections
Copyright © 2008
Version 4.0
Ch 10 - 27
Serial Cables
• One end of the serial cable is either a smart serial connector or a
DB-60 connector
• The other end is a large Winchester 15-pin connector
– V.35 connection to a Physical layer device such as a CSU/DSU
Smart serial
DB-60
Smart serial
Winchester block
Copyright © 2008
Version 4.0
Ch 10 - 28
Types of Devices
• Data terminal equipment (DTE)
– a device that receives clocking services from another device
– device is usually at the customer or the user end of the link
• Data communications equipment (DCE)
– a device that supplies the clocking service to another device
– device is typically at the WAN access provider end of the link
Copyright © 2008
Version 4.0
Ch 10 - 29
Serial WAN Connections in the Lab
• Routers are DTE devices by default, but they can be configured to
act as DCE devices
• Two routers can be connected together using a serial V.35 cable
– V.35 cables are available in DTE and DCE versions
Copyright © 2008
Version 4.0
Ch 10 - 30
Determining the Number of Hosts
• Every device needs an IP address
– consider present and future needs
• Segment the network based on host requirements
– number of hosts in a network or subnetwork is 2h – 2
Copyright © 2008
Version 4.0
Ch 10 - 31
Segmenting a Network
• Manage broadcast traffic
– divide one large broadcast domain into a number of smaller domains
– not every host need to receive every broadcast
• Different network requirements
– group users that share similar network or computing facilities together in
one subnet
• Security
– implement different levels of network security based on network
addresses
Copyright © 2008
Version 4.0
Ch 10 - 32
Creating Subnets
• Each subnet, is a physical segment, requires a router interface as
the gateway for that subnet
• Number of subnets on one networks is determined using 2n
– n is the number of bits
“borrowed” from the host bits to
create subnets
subnet 0
subnet 1
• Fixed length subnet mask
subnet 2
– one subnet mask for the entire
network
– each physical segment is
assigned an unique subnet
– each subnet has a same
number of usable (or valid) host
addresses
Copyright © 2008
Version 4.0
subnet 3
subnet 4
Ch 10 - 33
Designing an Address Standard
• Use addresses that fit a common pattern across all subnets can
assist troubleshooting and expedite adding new hosts
• Hosts can be categorized as general users, special users, network
resources, router LAN interfaces, router WAN links and
management access
• Document the IP addressing
scheme
Copyright © 2008
Version 4.0
Ch 10 - 34
Case Study 1
Calculating Addresses
Copyright © 2008
Version 4.0
Ch 10 - 35
Network Topology
Copyright © 2008
Version 4.0
Ch 10 - 36
Network Requirements
Computers
& servers
Router
(LAN gateway)
Student
460
1
20
481
Instructor
64
1
4
69
20 + 1
1
1
23
LAN
Administrator
Switches
(management)
Total
• WAN link
– router-to-router connection requires 2 host addresses
• There are 4 subnetworks in this topology
– student, instructor, administrator and WAN
Copyright © 2008
Version 4.0
Ch 10 - 37
Fixed Length Subnet Mask
• Require 9 host bits to support the largest number of host addresses
– 29 – 2 = 510 usable host addresses
– subnet mask is 255.255.254.0 (or /23 prefix)
• 2 bits are assigned for subnets  22 = 4 subnets
Copyright © 2008
Version 4.0
Ch 10 - 38
Variable Length Subnet Mask
• 172.16.0.0/22 is assigned to this network
• Refer to chapter 6, p51 on Using VLSM
Copyright © 2008
Version 4.0
Ch 10 - 39
Variable Length Subnet Mask (cont’d)
• Require 9 host bits to support the largest number of hosts
– mask is /23 prefix
• 1 bit is used for subnet to create 2 subnets
– 172.16.0.0/23 (subnet 0)
– 172.16.2.0/23 (subnet 1)
• Assign 172.16.0.0/23 (subnet 0) to Student LAN
• Instructor LAN has the next fewer hosts, i.e. 69 hosts
– require 7 host bits to accommodate 69 hosts
• Use 172.16.2.0/23 to create 4 more subnets
–
–
–
–
172.16.2.0/25 (subnet 0)
172.16.2.128/25 (subnet 1)
172.16.3.0 /25 (subnet 2)
172.16.3.128/25 (subnet 3)
Copyright © 2008
Version 4.0
Ch 10 - 40
Case Study 2
Calculating Addresses
Copyright © 2008
Version 4.0
Ch 10 - 41
Network Topology
Copyright © 2008
Version 4.0
Ch 10 - 42
VLSM
• Keep 5 host bits to accommodate the largest number of hosts
– 25 – 2 = 30 usable host addresses
– 3 bits are used to create 8 subnets (23 – 2)
• Network B will use 192.168.1.0/27 (subnet 0)
– valid range of host addresses is 192.168.1.1 to 192.168.1.30
• Network E will use 192.168.1.32/27 (subnet 1)
– valid range of host addresses is 192.168.1.33 to 192.168.1.62
• Network A will use 192.168.1.64/28 (subnet 0 in subnet 2)
– valid range of host addresses is 192.168.1.65 to 192.168.1.78
• Network D will use 192.168.1.80/28 (subnet 1 in subnet 2)
– valid range of host addresses is 192.168.1.81 to 192.168.1.94
• Network C will use 192.168.1.96/30 (subnet 0 in subnet 3)
– valid range of host addresses is 192.168.1.97 to 192.168.1.98
Copyright © 2008
Version 4.0
Ch 10 - 43
Creating Subnets
128
64
32
16
8
4
2
1
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
0
0
0
2
0
1
0
0
0
0
0
0
0
1
0
1
0
0
0
0
0
1
1
0
0
0
0
0
3
Copyright © 2008
Version 4.0
Ch 10 - 44
Device Interfaces
• LAN interfaces
– used for connecting UTP cables that terminate LAN devices such as
computers, switches and routers
– AUI, Ethernet and FastEthernet
• WAN interfaces
– used for connecting WAN devices to CSU/DSU
– serial and BRI
• Console interface
– provide configuration to the
device
• Auxiliary (AUX) interface
– a modem is connected to the
interface for remote
management
Copyright © 2008
Version 4.0
Ch 10 - 45
Device Management Connection
• A RJ-45 to DB-9 or RJ-45 to DB-25 adaptor is connected to the
EIA/TIA-232 serial port of the PC
– a rollover cable is used to connect the adapter to the device console
• The PC runs a program called a terminal emulator
– terminal emulator program, such as HyperTerminal, is used to access
the functions of a networking device
– COM port settings are 9600 bps, 8 data bits, no parity, 1 stop bit and no
flow control
• This provides out-of-band console access
• AUX port may be used for a modem-connected console
Copyright © 2008
Version 4.0
Ch 10 - 46
Accessing the Device Console
• Connect the RJ-45 to DB-9 adapter
to the console port using a rollover
cable
– newer computers that do not have
an EIA/TIA-232 serial interface will
need a USB-to-serial adapter
• The HyperTerminal program can be
accessed via Start  All Programs
 Accessories  Communications
– select the serial COM port and
configure the port settings as shown
• Power on the device and the bootup sequence will be displayed in the
HyperTerminal window
Copyright © 2008
Version 4.0
Ch 10 - 47