DHCP DNS

1
DHCP / DNS

• 3IMP
• Session 6

2
DHCP

• DHCP (Dynamic Host Configuration Protocol) is
  designed to make a network administrators job
  easier.
• It is a protocol that is designed to have
  workstations ask a server for an IP address when
  they boot up.
• The saves the administrator from having to
  manually assign an address to each individual
  machine.

3
DHCP

• The network administrator needs to setup the
  server of course, but at least you can have
  centralised administration of the addresses.
• How Does It Work?
• When a workstation uses DHCP it sends out a
  broadcast Discover packet.
• The server responds with an Offer packet. This
  packet has the configuration information in it.
• The client then uses a Request packet to the
  best (normally quickest, if there is more than 1
  DHCP server) server.
• The server will acknowledge (Ack) the client to
  confirm all is working.

4
DHCP
5
DHCP Information

• DHCP allows you send a huge variety of
  configuration information to clients. The most
  common types of information are
• IP Address
• Subnet Mask
• Gateway Address (IP address of a network point
  that acts as an entrance to another network. E.g.
  a proxy server acts as a gateway between a
  private network and the internet)
• DNS Server Address
• WINS Server Address
• Domain Name Suffix
• Lease Duration

6
DHCP
7
DHCP Types of Leases

• The two major types are
• Automatic These addresses are given to clients
  automatically, a client may receive a different
  IP address every time it boots.
• Manual (Reserved) These addresses are always
  given to the same host. The administrator needs
  to enter the MAC address into the DHCP server
  config as well the address to assign it and that
  host will always receive the same address, this
  is often used for servers.

8
APIPA - (Automatic Private IP Addressing)

• What if the DHCP server is unreachable? Even if
  everything else on the network is functioning
  properly, a client cannot communicate without a
  valid IP address.
• To address the possibility that computer might be
  configured to use DHCP but be unable to find a
  DHCP server, Microsoft offers Automatic Private
  IP Addressing for its Windows 98, Me, 2000, XP
  client and Windows 2003 server operating systems.
  
• As its name implies, APIPA (Automatic Private IP
  Addressing) provides a computer with an IP
  address automatically. Specifically, it assigns
  the computers network adapter an IP address from
  a pre-defined pool of addresses, 169.254.0.0
  through 169.254.255.255, that IANA (Internet
  Assigned Numbers Authority) has reserved for this
  purpose.

9
DNS - Domain Name System

• The Domain Name System, or DNS, is a service that
  translates computer names into IP addresses. A
  name-to-address system is necessary because we
  humans do not easily remember numbers like,
  "207.68.156.61", but we can easily remember names
  like, "www.microsoft.com".
• The DNS is a hierarchical system, with the top of
  the system called the "root", and represented by
  a single period ".". There are twelve (very, very
  busy) "root" servers on the Internet at the time
  of this writing. Root servers know where the
  servers are for the "top-level domains" like
  .com, .net, .edu, .org, .uk, .de, .nz, .us, and
  so on.

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How Does DNS Works

• To determine which primary name server contains
  your Domain Name Records, a local name server
  contacts the root domain name server maintained
  by the InterNIC.
• The root domain name server then returns the IP
  address of the primary name server responsible
  for the domain being requested.
• The primary name server becomes the next machine
  contacted by the local name server.
• The primary name server holds the IP address for
  the domain name and satisfies the the local name
  server's request.
• Then the local name server can finally return to
  the web browser with the IP address.
• Using the IP address, the web browser can then
  contact the company's web server and retrieve
  your web pages.

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How Does DNS Work
12
How Does DNS Work

• If that was the first lookup for that name, your
  local name server would temporarily record
  (cache) the details, and if asked again it would
  reply instantly.
• If you have a longer domain name, there may be
  more lookups required. The lookups basically go
  right to left in the domain name, eg.
  adel.tafe.sa.edu.au.

13
Dynamic DNS

• Most machines you contact are servers that have
  static IP addresses. Static DNS works well for
  these computers. That is someone has typed the
  configuration into a file.
• If a host receives its IP Address from a DHCP
  server Static DNS is no good. Dynamic DNS is the
  solution.
• There are two major ways this can work
• The DHCP server can inform the server of IP
  address assignment. This is normally done in
  campus networks.
• The host has client Dynamic DNS software that
  updates a DNS server. This is often done for home
  machines connected to broadband.

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Whats Next

• Next week we talk about transfer protocols,
  mainly FTP and HTTP.
• Today there are two DHCP labs see the next slide
  for some important setup instructions.

15
Setup the Virtual Machines

• Delete Existing VMs
• Run Virtual PC 2007 (start menu), remove all VMs
  and close Virtual PC
• Open Windows Explorer and delete all VMs from
  the E\
• To get new VMs
• Start gt Run gt \\HQ
• U/N E207 P/W Password1
• Browse to Virtual Machines gt Virtual PC
  2007gt3NWS Folder and copy the following to the
  E\ drive on your computer
• 1 Windows Server 2003 DC
• 2 XP Professional

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Setup the Virtual Server

• Go to the folder E\Windows Server 2003 DC and
  then double click the file Windows Server 2003 DC
• If an error message appears, click ok, then click
  the settings button on Virtual PC. Change the
  option for Hard disk 1 to E\Windows Server 2003
  DC (browse to the location).
• While in the virtual PC settings change the value
  for Networking to Local Only
• Click start to start your virtual PC (password is
  password)
• Give your virtual server the static IP address of
  192.168.0.102
• To do this go to Network Connection -gt Local Area
  Connection-gtProperties-gtTCP/IP-gtProperties-gt Use
  the following IP Address-gt192.168.0.102

17
Setup the Virtual Client

• Go to the folder E\XP Professional and then
  double click the file XP Professional
• Go to the virtual PC settings for the client
  machine and change the value for Networking to
  Local Only