book

Head First Networking

by Al Anderson, Ryan Benedetti

May 2009

Beginner

538 pages

10h 4m

English

O'Reilly Media, Inc.

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Head First Networking
Dedication
Advance Praise for Head First Networking
Praise for other Head First books
Authors of Head First Networking
How to Use this Book: Intro
Who is this book for?Who should probably back away from this book?We know what you’re thinkingWe know what your brain is thinkingMetacognition: thinking about thinkingHere’s what WE did:Here’s what YOU can do to bend your brain into submissionRead MeThe technical review teamAcknowledgmentsSafari® Books Online
1. Fixing Physical Networks: Walking on Wires
Coconut Airways has a network problemThe booking system network cable is bustedHow do we fix the cable?But how do we do this?Introducing the CAT-5 cableThe CAT-5 cable dissectedSo why are the pairs twisted?So what’s with all the colors?Let’s fix the broken CAT-5 cableA closer look at the RJ-45 connectorSo which wire goes where?So what are the physical steps?You fixed the CAT-5 cableCoconut Airways has more than one networkIntroducing the coaxial cableCoaxial networks are bus networksSo can we fix the cable?The network’s still not workingSo what goes on inside a coaxial cable?But what if there’s a break in the conductor?What about connectors and terminators?Use toner-tracer sets to listen to electronsNo sound means no electronsSo how do we find the continuity break?You’ve fixed the coaxial cableIntroducing fiber-optic cablesFiber-optics have connectors tooThe Coconut Airways cable’s over-bentSo what’s a fusion splicer?How to fix fiber-optics with a fusion splicerA fiber-optic connector needs fitting tooWe’re nearly ready to fix the connectorThere are two types of fiberSingle mode fiberMultimode fiberWhich mode fiber should you use?Let’s fit the connector on the fiber-opticSo which technique should we use?Coconut Airways is sky high
2. Planning Network Layouts: Networking in the Dark
Ghost Watch needs your help!Every good network needs a good planSo how does the device list help us plan a network?How to plan a network layoutLet’s plan the cabling with a floorplanReady to plot some network cables?So where have we got to?We need to decide on the cable management hardwareUh oh! The cabling is a messGhost Watch needs cable management hardwareThings that go bump...You’ve really cleaned up that noise and straightened out MOST of the cables!What’s in the closet?Let’s start by labeling the cablesBut there are still lots of cablesBut what else can we do?So what’s a patch panel?Behind the scenes of a patch panelThe wires go into a punch down blockRoll the cameras!
3. Tools and Troubleshooting: Into the Wire
Mighty Gumball won the Super Bowl contractA toner and tracer can check for a signal...... but can’t check for signal qualityIntroducing the multimeterUse a multimeter to measure resistanceSo what’s resistance?When resistance is lowWhen resistance is highSo how well did the multimeter do?An oscilloscope shows voltage changesVoltage is really electrical pressureSo how does this help us troubleshoot problems?Where does noise on network cables come from?So how well did the oscilloscope perform for Mighty Gumball?A logical analyzer uses voltage tooWhen is a logical analyzer useful?So which tool is best?The Mighty Gumball bonus went to JillA LAN analyzer combines the functions of all the other toolsA LAN analyzer understands the network traffic in the signalSo which tool is best?The Mighty Gumball problems are fixed!
4. Packet Analysis: You’ve Been Framed
What’s the secret message?So how do we extract a message from a signal?Network cards handle encodingSo how does the NIC encode the data?To get the message, reverse the encodingSo how do we decode the signal?The Ethernet standard tells hardware how to encode the dataA quick guide to binarySo how do we convert a binary to decimal?Computers read numbers, humans read lettersBut isn’t there an easier way?Hexadecimal to the rescueSo how do we convert a hexadecimal to decimal?We can convert to ASCII using hexBack at the spy agency...Protocols define the structure of a messageNetwork frames have lots of layersYour friendly packet field guideUDP Packet - Protocol Type 17ICMP Packet - Protocol Type 1TCP Packet - Protocol Type 6So can we decode the secret message?We’ve got all the right packets... but not necessarily in the right orderThe packet tells you the correct order

5. Network Devices and Traffic: How Smart is Your Network?
You’ve decoded the secret message......but how do we know who sent it?The packet information tells us where the packet came fromSo who’s the mole?There’s more to networks than computersHubs don’t change the MAC addressSo which device sent the packet to the hub?A hub sends signals, and sends them everywhereHubs think in terms of electricitySo what passed the signal to the hub?A switch sends frames, and only sends them where they need to goSwitches think in terms of framesSwitches store MAC addresses in a lookup table to keep the frames flowing smoothlyThe switch has the information...We can use software to monitor packetsLet’s hook Wireshark up to the switchWireshark gives us traffic informationRouters have MAC addresses tooWe’re closing in!You’ve found the mole!
6. Connecting Networks with Routers: Bringing Things Together
Networking Walking on the moonWe need to connect two networks togetherThe light’s on, but nobody’s homeWhat do you think the flashing LEDs have to do with traffic on the network?Let’s see what traffic is on our network!MAC address versus IP addressIP addresses give our networks a sense of location, and network nodes a sense of belonging to that locationWe retrieve IP addresses using the MAC address and the Address Resolution Protocol (ARP)So what’s the problem with the Moonbase?How do we get network traffic to move between networks?How the router moves data across networksBack to the Moonbase problemThe secret of IP numbers is...Routers connect networks by doing the math...Back at the Moonbase...Are you ready to program the router?You just created this router config file!Let the router tell us what’s wrong...
7. Routing Protocols: It’s a Matter of Protocol
Houston, we have a problem...Routing tables tell routers where to send packetsWe can see routes in the table using the show commandEach line represents a different routeSo how do we enter routes?Routes help routers figure out where to send network trafficSo are the moonbases now connected?Back on the moon...Moonbase 1 still has problemsSo how do we troubleshoot bad routes?We can start with the ping commandSo how does the ping command work?The traceroute command is useful tooSo what’s the problem with the network connection?The network address changes keep on coming...Use RIP to get routes to update themselvesSo what does this mean for Moonbase 1?So how do we set up RIP?But there’s still a problem...There are too many hopsThe routing protocol zooSo how do we setup EIGRP?We have lift off!
8. The Domain Name System: Names to Numbers
The Head First Health Club needs a websiteHello, my domain name is...So how do we get a domain name?Let’s go buy a domain nameUh-oh! We’re in troubleAnd she’s not the only oneIntroducing the DNSThe DNS relies on name serversHow the DNS sees your domainSo how does this affect the Health Club?First install a DNS name server......then configure the name serverThe anatomy of a DNS zone fileHere’s what the DNS zone file tells us about the Health Club serversThe Health Club can’t send emailsSo what’s the problem?Email servers use RDNS to fight SPAMCheck your sources with reverse DNSThe dig command can do a reverse DNS lookupYour name server has another important zone file...The emails are working!
9. Monitoring and Troubleshooting: Listen to Your Network’s Troubles
Pajama Death are back on tourSo here’s your challenge...So where would you start troubleshooting a misfiring network?Start troubleshooting your network problems by checking in with your network devicesTroubleshoot network connectivity with the ping commandIf you can ping, you get timingsBut what if you can’t ping?If the ping fails, check the cablesGet started with the show interface commandThe interface’s network statistics are a gold mine of troubleshooting informationThe ticket network’s still not fixedSNMP to the rescue!SNMP is a network admininistrator’s communication toolHow to configure SNMP on a Cisco deviceOne hour to go...Get devices to send you their problemsHow to configure syslogd on a Cisco deviceHow do you tell what’s in the logs?syslogd lets you fix problems before they’re problemsToo much information can be just as bad as not enoughWhat you need is relevant informationHow do you know which events are important?Pajama Death’s a sell-out!
10. Wireless Networking: Working Without Wires
Your new gig at Starbuzz CoffeeStarbuzz Coffee needs a wireless hotspotWireless access points create networks using radio wavesLet’s fit the wireless access pointWhat about the network configuration?So what’s DHCP?DHCP allocates IP addressesFirst make sure the client has DHCP turned on...Second, make the wireless access point a DHCP server......and then specify an acceptable range of IP addressesSo has setting up DHCP solved the problem?This time it’s personalWe’ve run out of IP addressesNAT works by reallocating IP addressesSo how do we configure NAT?So has this fixed the problem?There’s more than one wireless protocolMost newer access point support multiple protocolsSo is the Starbuzz wireless access point sorted?The central Starbuzz server needs to access the cash registerPort mapping to the rescue!So port mapping is a bit like NAT in reverseLet’s set up port mapping on the Starbuzz access pointThe wireless access point is a success!
11. Network Security: Get Defensive
The bad guys are everywhereThe evil impersonatorThe evil attackerAnd it’s not just the NETWORK that gets hurt...The evil eavesdropperThe big four in network securityDefend your network against MAC address spoofingSo how do we defend against MAC address spoofing?Defend your network against ARP poisoning attacksSo what can we do about ARP poisoning attacks?It’s all about the access, baby!If an attacker can get past your router, then he’s on your network!Set up your router’s Access Control Lists to keep attackers outSo how do we configure the Access Control List?Firewalls filter packets between networksPacket-filtering rules!Master the static packet filterGet smart with stateful packet-filtersHumans are the weakest link in your security chainSo how do social engineers operate?Smash social engineering with a clear and concise security policyYou’ve hardened your network
12. Designing Networks: You Gotta Have a Plan!
Now you have to plan a network from scratch!You have to know what the needs are before you can planSo you’ve developed your questions, now what?Look at your action planSo you have a physical layout, what’s next?Blueprints show everything in a building’s designYou may have to modify your network design based on what you see in the blueprints!So you’ve got your physical network layout, what’s next?You have got several options to segment this into two networksFinally, you need an implementation planLeaving town...It’s been great having you here in Networkville!
A. Leftovers: The Top Ten Things (we didn’t cover)
#1 Network topologiesStar topologyBus topologyToken Ring topology#2 Installing WiresharkWindows InstallMac OS X InstallLinux Install (Ubuntu)#3 How to get to the console or terminalWindowsLinuxMac OS X#4 The TCP Stack#5 VLANS#6 Cisco IOS Simulators#7 BGP#8 VPN#9 Intrusion Detection Systems#10 Cisco Certification
B. Ascii Tables: Looking Things Up
ASCII tables 0-31ASCII code tables 32-63ASCII code tables 64-95ASCII code tables 96-127
C. Installing Bind: Getting a Server to talk DNS
#1 Installing BIND on Windows (XP, 2000, Vista)#2 Installing BIND Mac OS X Server#3 Installing BIND Mac OS X Client & Linux
Index
About the Authors
Copyright

Content preview from Head First Networking

Chapter 7. Routing Protocols: It’s a Matter of Protocol

To build big networks, you need to use routers and they have to talk to each other.

Routers need to exchange routes with each other. They use various routing protocols to exchange routes. In the chapter, you will first see how to manually enter a route, then you will learn how to implement the simple RIP routing protocol. Finally you will learn how to setup EIGRP, an advanced routing protocol.

Houston, we have a problem...

So far, you’ve successfully hooked up the Moonbase network so that it can communicate with the ISS. There’s just one problem: there are actually 20 bases on the moon, and all the different moonbases need to keep in contact with each other through their network links in case they get into trouble. So is this possible?

When the international community started building the moonbases, they wisely decided to run fiber optic cables to all of the different moonbases. Each moonbase is directly connected to at least one other moonbase, and indirectly connected to all the others through the web of fiber optic cables. As an example, Moonbase 1 is directly connected to three other moonbases, and indirectly connected to all 20 others.

The Moonbase 1 router is able to send packets to the moonbases it’s directly connected to, but ...

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Head First Networking

by Al Anderson, Ryan Benedetti

Chapter 7. Routing Protocols: It’s a Matter of Protocol

Houston, we have a problem...

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.