Used ful level hy

1. DNS & DHCP

2. DNS
 DNS is an acronym of Domain Name System. As the name
suggests, DNS is a naming system that gives a name to any
computer or service connected to a network. DNS is utterly
important and everyone should use it. Without it, we’d
have to visit websites through their IP addresses, rather
than their domain. So, for example, if you wanted to visit
our website through it’s IP address, you’d have to go to
209.135.140.30. But with DNS, you can go to
rosehosting.com . It’s easier to remember and it’s more
user-friendly. That’s why people consider DNS “the phone
book of the Internet”. Nobody wants to remember an IP,
but everyone can and does remember a domain name.

3. Domain Name System (DNS)
DNS can be used to:
 Resolve host names to IP addresses
 Resolve IP addresses to host names
 Locate mail servers during email delivery

4. How Internet DNS Names Are
Resolved .root DNS
Microsoft.com DNS
.com DNS
What is the IP address of
www.microsoft.com?
1
2
3
4
Workstation
Local DNS Server
5
The IP address is
207.46.230.219

5. What Are DNS Queries?
DNS client
mail1.contoso.com
172.16.64.11
A recursive query is sent to a DNS server and
requires a complete answer
Local DNS server

6. What Are DNS Queries?
Client
Local
DNS server
Recursive query
mail1.contoso.com
172.16.64.11
Root hint (.)
.com
contoso.com
Iterative query
Ask .com
Iterative query
Authoritative response
Iterative query
Ask contoso.com

7. Task 1 DNS Zones Types
 Forward Lookup Zone
 Reverse Lookup Zone

8. DHCP
Dynamic Host Configuration Protocol

9. DHCP
 In IP environment, before a computer can
communicate to another one, they need to have
their own IP addresses.
 There are two ways of configuring an IP address on a
device:
 Static: Statically assign an IP address. This means we
manually type an IP address for this computer
 Dynamic Use a protocol so that the computer can obtain
its IP address automatically.

10. How does DHCP work?
 Lease Generation Process
 DORA Process
 Discover
 Offer
 Request
 Acknowledgement
 Four step Process

11. Benefits of Using DHCP
DHCP reduces the complexity and amount of administrative
work by using automatic IP configuration
Automatic IP Configuration Manual IP Configuration
IP addresses are supplied
automatically
IP addresses are entered manually
Correct configuration information
is ensured
IP address could be entered
incorrectly
Client configuration is updated
automatically
Communication and network
issues can result
A common source of network
problems is eliminated
Frequent computer moves
increase administrative effort

12. How DHCP Lease Generation Works
DHCP Server2
DHCP Server1 DHCP Client
1. DHCP client broadcasts a DHCPDISCOVER packet
2. DHCP servers broadcast a DHCPOFFER packet
3. DHCP client broadcasts a DHCPREQUEST packet
4. DHCP Server1 broadcasts a DHCPACK packet

13. DHCP Lease Renewal Process
 By default, lease period is limited to 8 days.
 Clients attempt to renew its lease as 50% of the lease
duration has expired.

14. DHCP
Lease

15. Missing DHCP Server
 If the client cannot find a DHCP server then It
may auto assign an IP address from a reserved
range 169.254.0.0 to 169.254.255.255 or simply
have an IP address of 0.0.0.0.

16. DHCP Commands
 ipconfig ./all -This command will show IP and DNS
settings
 ipconfig ./release -This command will release the IP
address from DHCP
 ipconfig ./renew -This command will renew the IP
address using DHCP