Networking, Part Two Two

Fiber Optic Ethernet

• Uses light to transmit data therefore immune to noise and grounding issues

• Up to 2000 meters cable length• Used for “backbone” runs• Half-duplex, so need two cables• Tends to be delicate, expensive and difficult to

use – shows up in data centers and seldom on desktops

• What is Verizon doing with Fios?

Fiber Terminations

Round ST

Square SC

Fiber Modes

• LED-based light source uses Multimode cable – multiple light signals at the same time each using a different reflection angle

• Good for short distances• Laser light-based use single-mode; high

transfer rates over long distances but rare• Most fiber cable is multimode; delicate and

expensive

Coax/BNC

• Old form of networking – did not require hub/switch; still used in cable modems, TV and satellite connections

• Type F connectors used in cable modems, etc. screw together

• BNC connectors are quarter-turn• Can be RG-6 or RG-59 (thinner); 75-ohm

impedance

Typical connection

Hubs

• Input on one port (does not matter which port)

• Signal is amplified and sent out on all ports• Easy way for long cable runs run-hub-run• Initially very expensive, have gotten cheaper

over time and are now seldom used

Switches

• Successor to hub• Automatically creates point-to-point

connection between any two ports• Again, price has come way down

Bridges

• Started out as hubs that could connect different media (coax and UTP)

• Developed into switches• Now have intelligence that can do simple

routing

NAS

• Network Attached Storage• Just shares files (hard disk storage)• Can be headless – no keyboard, video or

mouse• Use some form of Web interface to configure• Also called Network Appliance

Routers

• Must have at least two connections – one into a network and one out to another network

• Hello, CISCO; when you go beyond the home

Structured Cabling

• The idea is to create a safe, reliable cabling infrastructure for all of the devices that need interconnection

• Start with switches, cabling and PCs• Components of a network, such as how the

cable runs through the walls and where it ends up

• Connections leading outside your network• Standards from TIA/EIA

Structured Components

• Telcom room – place where all wires lead to• Horizontal cabling – from telcom room to PCs• Work areas – where the PCs are

Horizontal Cabling

• Use solid core wire – better conductor but stiff• Away from the dreaded vacuum cleaners!

Telco Room

• Equipment racks – from railroad days – 19” wide

• Tall: 1.75” – called a U• Devices are 1U, 2U or 4U – mostly• Patch Panels allow wiring punchdown on back

side and patch cables on the front side• Patch panels have CAT rating, so check it out

RJ-45 Jack Crimping

• Take Network+ , or follow the book’s figures• EZ-RJ-45 jacks may be more expensive, but

they are worth every penny

Work Area

• Wall plate to terminate horizontal run• Plates have CAT ratings too• Mike suggests looking here first if the user has

lost connection to the network

TCP/IP review

• Dotted decimal notation• Subnet mask to identify network number and

node number• Class A: 1-126• Class B: 128-191• Class C: 192-223• TCP is connection-oriented; UDP is

connectionless (User Datagram Protocol)

TCP/IP Services

• HTTP – HyperText Transfer Protocol• Telnet – Allows remote access to a device• Ping – Can one host reach another?• Tracert – How to get from one point to

another• Most services are command-line based

DHCP

• Dynamic Host Configuration Protocol• Will assign IP address, DNS server(s) and other

configuration data• Your home router does this function

Automatic Private Addressing

• Automatic Private IP Addressing (APIPA)• When you can’t see (reach) a DHCP server• 169.254.X.X - X and X are random numbers

less than 255• Will broadcast the address to see if anyone

else is using it• Can only talk to other 169.254’s

IPv6

• Not just a superset of IPv4; uses 128 bits• Always has eight groups of four hexadecimal

characters• Leading zeros can be dropped from any group• Can drop group(s) of zeros and replace with :: -

but only once in an address• V6 loopback address ::1• Subnet mask uses Classless Inter-Domain Routing

(CIDR) where /x is the number of bits in mask

More IPv6

• Computer boots and assigns itself a link-local address (FE80:: ) – first 64 bits

IPv6

• Last part of address is, for Windows, a random value for the last 64 bits.

• Another way to do it is to use MAC address called Extended Unique Identifier, 64 bit or EUI-64

• The last 64 bits are node so subnet is never longer than /64

• IANA passes out /32 subnets to big ISPs and end users; ISPs had out /48 and /64 subnets

• Subnet Masks are mostly between /48 and /64

Global Addresses

• Need a GA to get to Internet• Easiest way is to request it from default

gateway router with Router Solicitation message (FF02::2)

• Router responds with Router Advertisement which is its network ID and subnet (and DNS)

• Computer generates the rest of address as before (random or MAC)

Wired Network

• NIC – The physical hardware that connects the computer system to the network media

• Protocol – The language that the computer systems use to communicate

• Network Client – The interface that allows the computer system to speak to the protocol

NIC

• Expansion card or built-into the motherboard• Windows will recognize, configure and provide

driver(s) for most current NICs• If not, Add Hardware Wizard will automatically

run and ask for driver media• If you have to run the Add Hardware Wizard, you

did something really, really wrong• Duplex – both talk and listen• Half-duplex – talk or listen

Link Lights

• Can have one to four, any color(s)• Give status – something will light up when

cable is connected at both ends• If no lights, you have network problems to fix

(first place to look)• Switches also have link lights so you can check

both ends of connection• Solid green means connectivity; flashing green

means intermittent connectivity

Wake on LAN

• Send either a special pattern or “magic packet”

• Have to configure both Windows (network) and CMOS to have this work

Sharing Drives and Folders

• Set both the Network and NTFS permissions; set Network to everyone full control then tune with NTFS permissions

• Can map a network location to a drive letter• Make sure File and Printer Sharing is turned

on

UNC

• Universal Naming Convention : universal to Microsoft anyway

• \\server\resource

NET command

• Type NET at command prompt

NBTSTAT

• NetBIOS over TCP/IP Statistics• NetBIOS long gone but command remains• Useful to see what is connected to network

Troubleshooting

• For exams: it is getting a computer back on the network

• Need to take a giant leap up in quality of skills• Is it the computer, the network, or both?

Losing Physical Connectivity

• Pretty obvious in Windows with red Xs and dialog boxes

• Can also find link lights out on network connection

• Is cable unplugged at either end?• Is NIC disabled in Device Manager?• If you only see yourself in Network Discovery• Check if any other stations are down• Failed NIC can lose connectivity

Cable Testing

• Many disconnect problems are in the patch cable to the wall

• Midrange Time-Domain Reflectometer (TDR) can be handy to pinpoint break in cable

• Replace the whole cable, don’t try to patch it (pun intended!)

• Use a tone-tester to find other end of a cable

Fail to connect to New Resource

• Often a configuration issue – make sure it is shared correctly

• Make sure you have valid user and password • Do you have permission(s)?• Correct homegroup/domain/workgroup?

Fail to connect to used resource

• Try nbtstat –s• Try net view• Check that serving system is on and connected

to network