Network Administration

Table of Contents

1. Network Administration Fundamentals

Introducing the TCP/IP Model

The Physical Layer

The MAC Layer

The Network Layer

The Transport Layer

The Application Layer

The OSI Model

Relating the TCP and OSI Models

Overview of how the TCP/IP Model Works

A deeper look at the TCP protocol layers

Network Layer and Understanding IP addressing

Choosing the Class of network that you will use

Why use sub-netting

Summary - TCP/IP Stack

Transferring information across the Internet

Test the network with Ping

Creating and using the ARP table

Explaining routers

Briefly on LAN 's and WAN's

How to put an IP address onto your network card

Exercise:

Lets look at ping from the TCP/IP Stack point of view

Packets, frames, bytes, octets and datagrams

The network interfaces that you'll see if you run ifconfig -a

Setting up multiple cards in one machine

Logical and physical networks

Plumbing a device

Routing and using the "netstat" command

Wrap-up

CIDR

Further Troubleshooting with ping and arp

2. Client/Server Technology

Client / Server enhancing Performance

Client / Server enhancing Scalability

Client / Server enhancing Flexibility

Client / Server offers Interoperability

First Example:

Second example:

Central Control

Third example:

Fourth example:

Fifth example:

Client / Server implemented with RPC

3. Network Architecture

Logical versus physical network layout

Physical Network

Logical Network

The difference?

How do we connect the machines Physically

Token Ring

Ethernet

Understanding CSMA/CD

Maximum transmission unit (MTU)

Process that can only talk MAC address to MAC address.

Broadcasts, Unicasts and Multicasts

What is a BROADCAST?

What is a UNICAST?

What is a MULTICAST?

Why is there a distinction?

Services that are UNICAST (ssh/telnet/ftp) and broadcast (DHCP/BOOTP/ARP)

ARP and the ARP table

What is ARP?

arping

LAN versus WAN

To define a LAN

To define a WAN

What technology must we look at when using a WAN

Hubs, switches and bridges

Routers and gateways

Broadcast versus collision domains

The concept of broadcast and collision domain

How to restrict the broadcast domain.

4. IP Address Allocation

Static IP addressing

Changing IP addresses on the fly

Plumbing a network card

Explain on-the-fly vs permanent changes (i.e. Changing Configuration files)

Dynamic Host Configuration Protocol

What is it?

Boot Protocol

How does DHCP work?

Why DHCP is restricted to a broadcast domain

Explain "dhclient"

How to obtain the address of the DHCP server

In Conclusion:

5. Basic Network Configuration

The ifconfig command

The loopback interface

Understanding the Dynamic Host Configuration Protocol (DHCP)

DHCP offers the following benefits:

6. Electronic Mail

Email follows the client/server model

MTA and MUA

Exchanging email's

SMTP

Open Relays and SPAM

Retrieving email

Category 1: We are a user on the host that is also the SMTP server.

Category 2: We are a user on another host on the same Intranet as the SMTP server

Category 3: Your email resides at an ISP.

Troubleshooting email problems

Security Issues

Introduction

GNU Privacy Guard (GPG)

Preamble to signing, encryption and verification

Digital signatures

Sharing your public key.

Verifying keys

The web of trust

7. Domain Naming System

What is DNS?

What do we use DNS for?

Describe the name resolution process

The host file

DNS Name Server

NIS

So where to look up the host name?

Types of records in a DNS

Forward versus reverse name resolution

Describe round robin DNS servers

Troubleshooting your DNS client configuration

Is it a DNS problem?

Ensure names resolved from the correct place

Using NSLOOKUP

Using DIG, Why use DIG? How to use DIG? Examples

8. SAMBA

What you will need.

Using smbclient

Smbmount/smbumount

Nmblookup

Smbtar

9. Basic network troubleshooting

PING

Reaching other devices (hosts)

Understanding PING, (responses and statistics)

Regulating the number of packets sent with PING

Response or error message

IP Address and Name resolution problems

Verifying Your Routing Table

Summary

10. Basics of network security

Terminology

Firewall / Trusted and Untrusted Networks

Basic explanation - relating NAT to problems with IPv4

Checking on listening ports.

Service level security

TCP Wrappers

11. Network, System and Service Security

User security

Service level security

Inetd:

Xinetd:

Configuration of tcp-wrappers

Troubleshooting TCP-wrappers

12. Network File System (NFS)

What is NFS?

How can we use NFS?

Configuring NFS

Network Information Service (NIS)

Master/Slave NIS and redundancy

Configuration of NIS clients

Where is NIS used?

To summarize NFS and NIS

Downside of NFS and NIS

13. Remote access

Inherent problems with telnet

SSH

Public and Private Key Infrastructure

Sample Session for Generating a key

Sample Session for Accepting a fingerprint

Sample Session for Verifying a fingerprint

Sample Session Using ssh agent

Sample Session to destroy your public/private key pair

FTP

Exercises:

14. Connecting remotely to the X Window System

Introduction

Widgets

So here we are:

Some practice

15. Connecting to an ISP

Introduction

Before we begin:

Checklist

A. Practical lab

Index