Network+ : Network Models

  1. Network+ Certification (N10-007): Syllabus
  2. Network+ : Introductions and Resources
  3. Network+ : Network Models
  4. Network+: Cabling
  5. Network+ : Topologies
  6. Network+ : Ethernet Basics
  7. Network+ : Contemporary Ethernet
  8. Network+ : Installing a Physical Network
  9. Network+ : Booting and Getting On the Network
  10. Network+ : TCP/IP Basics
  11. Network+ : Subnetting
  12. Network+: Routing Protocols
  13. Network+ : Routing and Firewalls
  14. Network+ : TCP/IP Ports and Applications
  15. Network+ : Network Naming and Sharing Resources
  16. Network+ : Secure Networking
  17. Network+ : Advanced Networking Devices
  18. Network+ : IPv6
  19. Network+ : Remote Connectivity
  20. Network+ : WiFi
  21. Network+ : Virtualization
  22. Network+ : Mobile Networking
  23. Network+ : Building a Real-World Network
  24. Network+ : Managing Risk
  25. Network+ : Protecting Your Network
  26. Network+ : Network Monitoring
  27. Network+ : Network Troubleshooting
  28. Network+: Network Monitoring

Unit 3

Chapter 1

Network Commands

arp   #  (Linux and Windows)

ping   # (Linux and Windows)

ipconfig # (Windows)

ifconfig # (old Linux command; deprecated)

ip # (new Linux command)

iwconfig # (Linux wifi)

nslookup  # (Linux and Windows)

dig # (Linux native, Windows installable)

traceroute # (Linux)

tracert # (Windows)

net  #  (Windows)

netstat # (Windows and Linux)

nbtstat # (Windows)

netsh  #  (Windows)


Client / Server Model


Clients: Either a physical machine like your PC or workstation, or more accurately, a “receiving end” application like your web browser. The client will connect to the server’s IP address and the service’s port number, eg.

Servers: either physical machines or service daemons, like web servers, mail servers, streaming servers, etc.). The server will accept connections from clients at the server’s IP address and port number.

There’s more to this, so don’t forget this model.

Local Area Networks (LANs)

The TCP/IP Model and the OSI Model


Layer 1 of the OSI Model: the Physical Layer

Physical media: What carries the signal (think of telegraph wire)

            • Wire
            • Fiber optic cable
            • Radio waves
            • Infrared

Layer 2: The Data Link Layer

Layer 2 of the OSI is … a mistake. ISO ignores the fact that there are two protocols at work there: a Logical Link Control layer that sets up sessions and handles multiplexing, and a Media Access Control layer that handles addressing using MAC addresses.

Logical Link Control (LLC)

Media Access Control (MAC)

MAC Addresses

NICs have “permanent” hardware addresses (Physical Addresses in Windows): MAC Addresses.

All local network traffic is sent to and from MAC Addresses. Think of them as the room numbers in a hotel, used for things like Room Service.


Mac Addresses are written in hexadecimal:

Base 16 notation, using 0-9 and A-F to express numbers from 0-15:

0 1 2 3 4 5 6 7 8 9 a b c d e f

Grouped in six pairs of hex numbers with a separator in between:

Generic hex numbers in the wild look like this:

0f38  – just the number

0x0f38 – “0x” means “hex”

0f38h – “h” means “hex”

So actual MAC addresses look like this:




The formal specification for MAC addresses calls for them to be lower-case letters, BUT: Microsoft will and CompTIA may show them as upper-case letters.
And the delimiter can be a colon ( : ), a dash ( – ), or anything else. The delimiters aren’t really there; they are put in for our feeble human minds.

Signal Protocols: How the message gets passed (think of Morse Code)

Ethernet, Token Ring, DECnet, X.25, IPXSPX, Banyan Vines, etc.

Today, mostly Ethernet

Ethernet passes frames. (You could call them packets, but the other kids on the playground will make fun of you.)

Ethernet cards are NICs (network interface cards, also called “host adapters”).

Full vs. Half-duplex

It wasn’t until we got switches that we could use full duplex communication. In other words, both hosts can talk non-stop, and listen non-stop, full-time, with no collisions!

This was a huge step. Every session between hosts is on its own private collision domain: there ARE no collisions. Ethernet became hugely faster with this innovation.

LAN Models and Network Operating Systems

The oldest network model:




Network Operating Systems


        • Client/Server
        • Peer-to-Peer
        • Resource-Based (Workgroup)
        • Server-Based (Domain)
        • Organization-Based (Directory)
LAN Manager (LM) – 3Com and MS:



LAN only, using MAC addresses for addressing and NetBios for naming.

NetBIOS name: 15 chars. max

NetBIOS NW Model:


NetBIOS (naming)

NetBEUI (addressing)




LAN only


A cheat to resolve NetBIOS names across IP subnets. Normally NetBIOS stuff is confined to the local network.