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Head First Networking

Cover of Head First Networking by Al Anderson... Published by O'Reilly Media, Inc.
  1. Dedication
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  3. Advance Praise for <span xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:pls="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:ssml="http://www.w3.org/2001/10/synthesis" xmlns:svg="http://www.w3.org/2000/svg" class="emphasis"><em>Head First Networking</em></span>
  4. Praise for other <span xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:pls="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:ssml="http://www.w3.org/2001/10/synthesis" xmlns:svg="http://www.w3.org/2000/svg" class="emphasis"><em>Head First</em></span> books books
  5. Authors of Head First Networking
  6. How to Use this Book: Intro
    1. Who is this book for?
      1. Who should probably back away from this book?
    2. We know what you’re thinking
    3. We know what your brain is thinking
    4. Metacognition: thinking about thinking
    5. Here’s what WE did:
    6. Here’s what YOU can do to bend your brain into submission
    7. Read Me
    8. The technical review team
    9. Acknowledgments
    10. Safari<sup xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:pls="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:ssml="http://www.w3.org/2001/10/synthesis" xmlns:svg="http://www.w3.org/2000/svg">&#174;</sup> Books Online Books Online
  7. 1. Fixing Physical Networks: Walking on Wires
    1. Coconut Airways has a network problem
      1. The booking system network cable is busted
    2. How do we fix the cable?
      1. But how do we do this?
    3. Introducing the CAT-5 cable
    4. The CAT-5 cable dissected
      1. So why are the pairs twisted?
    5. So what’s with all the colors?
    6. Let’s fix the broken CAT-5 cable
    7. A closer look at the RJ-45 connector
      1. So which wire goes where?
    8. So what are the physical steps?
    9. You fixed the CAT-5 cable
    10. Coconut Airways has more than one network
    11. Introducing the coaxial cable
    12. Coaxial networks are bus networks
    13. So can we fix the cable?
    14. The network’s still not working
    15. So what goes on inside a coaxial cable?
      1. But what if there’s a break in the conductor?
    16. What about connectors and terminators?
    17. Use toner-tracer sets to listen to electrons
    18. No sound means no electrons
      1. So how do we find the continuity break?
    19. You’ve fixed the coaxial cable
    20. Introducing fiber-optic cables
      1. Fiber-optics have connectors too
    21. The Coconut Airways cable’s over-bent
      1. So what’s a fusion splicer?
    22. How to fix fiber-optics with a fusion splicer
    23. A fiber-optic connector needs fitting too
    24. We’re nearly ready to fix the connector
    25. There are two types of fiber
      1. Single mode fiber
      2. Multimode fiber
    26. Which mode fiber should you use?
    27. Let’s fit the connector on the fiber-optic
      1. So which technique should we use?
    28. Coconut Airways is sky high
  8. 2. Planning Network Layouts: Networking in the Dark
    1. Ghost Watch needs your help!
    2. Every good network needs a good plan
    3. So how does the device list help us plan a network?
    4. How to plan a network layout
    5. Let’s plan the cabling with a floorplan
    6. Ready to plot some network cables?
    7. So where have we got to?
    8. We need to decide on the cable management hardware
    9. Uh oh! The cabling is a mess
    10. Ghost Watch needs cable management hardware
    11. Things that go bump...
    12. You’ve really cleaned up that noise and straightened out <span xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:pls="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:ssml="http://www.w3.org/2001/10/synthesis" xmlns:svg="http://www.w3.org/2000/svg" class="underline">MOST</span> of the cables! of the cables!
      1. What’s in the closet?
    13. Let’s start by labeling the cables
    14. But there are still lots of cables
      1. But what else can we do?
    15. So what’s a patch panel?
    16. Behind the scenes of a patch panel
    17. The wires go into a punch down block
    18. Roll the cameras!
  9. 3. Tools and Troubleshooting: Into the Wire
    1. Mighty Gumball won the Super Bowl contract
    2. A toner and tracer can check for a signal...
    3. ... but can’t check for signal quality
    4. Introducing the multimeter
      1. Use a multimeter to measure resistance
    5. So what’s resistance?
      1. When resistance is low
      2. When resistance is high
    6. So how well did the multimeter do?
    7. An oscilloscope shows voltage changes
    8. Voltage is really electrical pressure
      1. So how does this help us troubleshoot problems?
    9. Where does noise on network cables come from?
    10. So how well did the oscilloscope perform for Mighty Gumball?
    11. A logical analyzer uses voltage too
    12. When is a logical analyzer useful?
    13. So which tool is best?
    14. The Mighty Gumball bonus went to Jill
    15. A LAN analyzer combines the functions of all the other tools
    16. A LAN analyzer understands the network traffic in the signal
    17. So which tool is best?
    18. The Mighty Gumball problems are fixed!
  10. 4. Packet Analysis: You’ve Been Framed
    1. What’s the secret message?
      1. So how do we extract a message from a signal?
    2. Network cards handle encoding
      1. So how does the NIC encode the data?
    3. To get the message, reverse the encoding
      1. So how do we decode the signal?
    4. The Ethernet standard tells hardware how to encode the data
    5. A quick guide to binary
      1. So how do we convert a binary to decimal?
    6. Computers read numbers, humans read letters
      1. But isn’t there an easier way?
    7. Hexadecimal to the rescue
      1. So how do we convert a hexadecimal to decimal?
    8. We can convert to ASCII using hex
    9. Back at the spy agency...
    10. Protocols define the structure of a message
    11. Network frames have lots of layers
    12. Your friendly packet field guide
      1. UDP Packet - Protocol Type 17
      2. ICMP Packet - Protocol Type 1
      3. TCP Packet - Protocol Type 6
    13. So can we decode the secret message?
    14. We’ve got all the right packets... but not necessarily in the right order
    15. The packet tells you the correct order
  11. 5. Network Devices and Traffic: How Smart is Your Network?
    1. You’ve decoded the secret message...
      1. ...but how do we know who sent it?
    2. The packet information tells us where the packet came from
    3. So who’s the mole?
    4. There’s more to networks than computers
    5. Hubs don’t change the MAC address
      1. So which device sent the packet to the hub?
    6. A hub sends signals, and sends them <span xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:pls="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:ssml="http://www.w3.org/2001/10/synthesis" xmlns:svg="http://www.w3.org/2000/svg" class="underline">everywhere</span>
      1. Hubs think in terms of electricity
    7. So what passed the signal to the hub?
    8. A switch sends frames, and only sends them where they need to go
      1. Switches think in terms of frames
    9. Switches store MAC addresses in a lookup table to keep the frames flowing smoothly
    10. The switch has the information...
    11. We can use software to monitor packets
    12. Let’s hook Wireshark up to the switch
    13. Wireshark gives us traffic information
    14. Routers have MAC addresses too
    15. We’re closing in!
    16. You’ve found the mole!
  12. 6. Connecting Networks with Routers: Bringing Things Together
    1. Networking <span xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:pls="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:ssml="http://www.w3.org/2001/10/synthesis" xmlns:svg="http://www.w3.org/2000/svg" class="strikethrough">Walking</span> on the moon on the moon
    2. We need to connect two networks together
    3. The light’s on, but nobody’s home
      1. What do you think the flashing LEDs have to do with traffic on the network?
    4. Let’s see what traffic is on our network!
    5. MAC address versus IP address
    6. IP addresses give our networks a sense of location, and network nodes a sense of belonging to that location
    7. We retrieve IP addresses using the MAC address and the Address Resolution Protocol (ARP)
    8. So what’s the problem with the Moonbase?
    9. How do we get network traffic to move between networks?
    10. How the router moves data across networks
    11. Back to the Moonbase problem
    12. The secret of IP numbers is...
    13. Routers connect networks by doing the math...
    14. Back at the Moonbase...
    15. Are you ready to program the router?
    16. You just created this router config file!
    17. Let the router tell us what’s wrong...
  13. 7. Routing Protocols: It’s a Matter of Protocol
    1. Houston, we have a problem...
    2. Routing tables tell routers where to send packets
      1. We can see routes in the table using the show command
    3. Each line represents a different route
    4. So how do we enter routes?
    5. Routes help routers figure out where to send network traffic
    6. So are the moonbases now connected?
    7. Back on the moon...
      1. Moonbase 1 still has problems
    8. So how do we troubleshoot bad routes?
      1. We can start with the ping command
      2. So how does the ping command work?
    9. The traceroute command is useful too
    10. So what’s the problem with the network connection?
    11. The network address changes keep on coming...
    12. Use RIP to get routes to update themselves
      1. So what does this mean for Moonbase 1?
    13. So how do we set up RIP?
    14. But there’s still a problem...
    15. There are too many hops
    16. The routing protocol zoo
    17. So how do we setup EIGRP?
    18. We have lift off!
  14. 8. The Domain Name System: Names to Numbers
    1. The Head First Health Club needs a website
    2. Hello, my domain name is...
      1. So how do we get a domain name?
    3. Let’s go buy a domain name
    4. Uh-oh! We’re in trouble
      1. And she’s not the only one
    5. Introducing the DNS
    6. The DNS relies on name servers
    7. How the DNS sees your domain
    8. So how does this affect the Health Club?
    9. First install a DNS name server...
    10. ...then configure the name server
    11. The anatomy of a DNS zone file
    12. Here’s what the DNS zone file tells us about the Health Club servers
    13. The Health Club can’t send emails
    14. So what’s the problem?
    15. Email servers use RDNS to fight SPAM
    16. Check your sources with reverse DNS
    17. The dig command can do a reverse DNS lookup
    18. Your name server has another important zone file...
    19. The emails are working!
  15. 9. Monitoring and Troubleshooting: Listen to Your Network’s Troubles
    1. Pajama Death are back on tour
      1. So here’s your challenge...
    2. So where would you start troubleshooting a misfiring network?
    3. Start troubleshooting your network problems by checking in with your network devices
    4. Troubleshoot network connectivity with the ping command
      1. If you can ping, you get timings
      2. But what if you can’t ping?
    5. If the ping fails, check the cables
    6. Get started with the show interface command
      1. The interface’s network statistics are a gold mine of troubleshooting information
    7. The ticket network’s still not fixed
    8. SNMP to the rescue!
    9. SNMP is a network admininistrator’s communication tool
    10. How to configure SNMP on a Cisco device
    11. One hour to go...
    12. Get devices to send you their problems
    13. How to configure syslogd on a Cisco device
    14. How do you tell what’s in the logs?
      1. syslogd lets you fix problems before they’re problems
    15. Too much information can be just as bad as not enough
      1. What you need is <span xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:pls="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:ssml="http://www.w3.org/2001/10/synthesis" xmlns:svg="http://www.w3.org/2000/svg" class="underline">relevant</span> information information
    16. How do you know which events are important?
    17. Pajama Death’s a sell-out!
  16. 10. Wireless Networking: Working Without Wires
    1. Your new gig at Starbuzz Coffee
      1. Starbuzz Coffee needs a wireless hotspot
    2. Wireless access points create networks using radio waves
    3. Let’s fit the wireless access point
    4. What about the network configuration?
    5. So what’s DHCP?
      1. DHCP allocates IP addresses
    6. First make sure the client has DHCP turned on...
    7. Second, make the wireless access point a DHCP server...
    8. ...and then specify an acceptable range of IP addresses
    9. So has setting up DHCP solved the problem?
    10. This time it’s personal
    11. We’ve run out of IP addresses
    12. NAT works by reallocating IP addresses
    13. So how do we configure NAT?
    14. So has this fixed the problem?
    15. There’s more than one wireless protocol
      1. Most newer access point support multiple protocols
      2. So is the Starbuzz wireless access point sorted?
    16. The central Starbuzz server needs to access the cash register
    17. Port mapping to the rescue!
      1. So port mapping is a bit like NAT in reverse
    18. Let’s set up port mapping on the Starbuzz access point
    19. The wireless access point is a success!
  17. 11. Network Security: Get Defensive
    1. The bad guys are everywhere
      1. The evil impersonator
      2. The evil attacker
    2. And it’s not just the NETWORK that gets hurt...
      1. The evil eavesdropper
    3. The big four in network security
    4. Defend your network against MAC address spoofing
    5. So how do we defend against MAC address spoofing?
    6. Defend your network against ARP poisoning attacks
    7. So what can we do about ARP poisoning attacks?
    8. It’s all about the access, baby!
      1. If an attacker can get past your router, then he’s on your network!
    9. Set up your router’s Access Control Lists to keep attackers out
    10. So how do we configure the Access Control List?
    11. Firewalls filter packets between networks
    12. Packet-filtering rules!
    13. Master the static packet filter
    14. Get smart with stateful packet-filters
    15. Humans are the weakest link in your security chain
    16. So how do social engineers operate?
    17. Smash social engineering with a clear and concise security policy
    18. You’ve hardened your network
  18. 12. Designing Networks: You Gotta Have a Plan!
    1. Now you have to plan a network from scratch!
    2. You have to know what the needs are before you can plan
    3. So you’ve developed your questions, now what?
    4. Look at your action plan
    5. So you have a physical layout, what’s next?
    6. Blueprints show everything in a building’s design
    7. You may have to modify your network design based on what you see in the blueprints!
    8. So you’ve got your physical network layout, what’s next?
      1. You have got several options to segment this into two networks
    9. Finally, you need an implementation plan
    10. Leaving town...
    11. It’s been great having you here in Networkville!
  19. A. Leftovers: The Top Ten Things (we didn’t cover)
    1. #1 Network topologies
      1. Star topology
      2. Bus topology
      3. Token Ring topology
    2. #2 Installing Wireshark
      1. Windows Install
      2. Mac OS X Install
      3. Linux Install (Ubuntu)
    3. #3 How to get to the console or terminal
      1. Windows
      2. Linux
      3. Mac OS X
    4. #4 The TCP Stack
    5. #5 VLANS
    6. #6 Cisco IOS Simulators
    7. #7 BGP
    8. #8 VPN
    9. #9 Intrusion Detection Systems
    10. #10 Cisco Certification
  20. B. Ascii Tables: Looking Things Up
    1. ASCII tables 0-31
    2. ASCII code tables 32-63
    3. ASCII code tables 64-95
    4. ASCII code tables 96-127
  21. C. Installing Bind: Getting a Server to talk DNS
    1. #1 Installing BIND on Windows (XP, 2000, Vista)
    2. #2 Installing BIND Mac OS X Server
    3. #3 Installing BIND Mac OS X Client & Linux
  22. Index
  23. About the Authors
  24. Special Upgrade Offer
  25. Copyright
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Chapter 7. Routing Protocols: It’s a Matter of Protocol

image with no caption

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.

image with no caption

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

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