Chapter 10 Planning and Cabling Networks

Copyright © 2008 Version 4.0 Ch 10 - 1

Chapter 10

Planning and Cabling Networks

CCNA ExplorationNetwork Fundamentals


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– LAN and WAN

interfaces

hub

switch

router

router

switch


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


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


Device Selection Factors

• Cost • Speed and types of ports/interfaces • Expandability • Manageability • Additional features and services


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


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


Speed and Type of Ports (Interfaces)

• Purchasing decisions– just enough ports for today’s needs

– mixture of UTP speeds

– both UTP and fiber ports


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


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


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



• 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



• 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


Types of Media

• UTP (Category 5, 5e, 6 and 7)

• Fiber optics

• Wireless


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?


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


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


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


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


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


UTP Cabling Connections

• Specified by the Electronics Industry Alliance/Telecommunications Industry Association (EIA/TIA)


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


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


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


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


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


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


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

Winchester block

Smart serial


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


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


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


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


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

subnet 0

subnet 1

subnet 2

subnet 3

subnet 4

– n is the number of bits “borrowed” from the host bits to create subnets

• Fixed length subnet mask– 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


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


Case Study 1

Calculating Addresses


Network Topology


Network Requirements

• WAN link

– router-to-router connection requires 2 host addresses

• There are 4 subnetworks in this topology– student, instructor, administrator and WAN

LANComputers & servers

Router

(LAN gateway)

Switches

(management) Total

Student 460 1 20 481

Instructor 64 1 4 69

Administrator 20 + 1 1 1 23


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


Variable Length Subnet Mask

• 172.16.0.0/22 is assigned to this network • Refer to chapter 6, p51 on Using VLSM


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)


Case Study 2

Calculating Addresses


Network Topology


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


Creating Subnets

128 64 32 16 8 4 2 1

0 0 0 0 0 0 0 0

0 0 1 0 0 0 0 0

0 1 0 0 0 0 0 0

0 1 0 1 0 0 0 0

0 1 1 0 0 0 0 0

0

1

2

3


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


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


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 boot-up sequence will be displayed in the HyperTerminal window

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Chapter 10 Planning and Cabling Networks