1. Planning the Addressing Structure
Working at a Small-to-Medium Business or ISP – Chapter 4

2. Implementation of IP Addressing in the LAN
IP addresses are made up of 32 total bits
divided into 4 octets with a decimal separating them
AKA: dotted decimal notation

3. IP Address and Binary Review
In an 8 bit binary number, what is the total number of combinations of the eight bits?
256 combinations = 28
Convert 230 into binary.

4. IP Addressing IP addresses are HIERARCHIAL (like a family tree)
there are parents (networks)
there are children (hosts)

5. IP Address Classes Classes A – C Class D – reserved for multicasts
assigned to users
Class D – reserved for multicasts
Class E -- reserved for experimental use

6. IP Address Classes Classful IP Addresses
The number of bits used to identify the hosts is fixed by the class of the network
All subnets in a network are the same size.

7. Private & Public IP Addressing
Public Addressing - Public IP addresses must be unique across the entire Internet.
Private IP addresses assigned by IETF (Internet Engineering Task Force)
reduces the number of public IP addresses assigned to organizations

8. Implementation of IP Addressing in the LAN
SUBNETS

9. Lets Learn How To Subnet
Subnet – Take a network address and break it apart to better fit your network setup and structure.
Subnet Help Sheets Are Your Friend

11. IP Addressing Practice
Class C address with a default subnet mask.
Question 1 – What is the default subnet mask
Question 2 – How many usable hosts are available?
254
IPv4
Question 1 – Class which provides the largest number of network bits?

12. IP Addressing Practice
Class B address
Question 1 – What is the default subnet mask
Question 2 – The IP address is with a default subnet mask. What is the broadcast address for this network? – Change all Host bits to 255.
IPv4
Question 1 – The IP address is with a subnet mask of What is the maximum number of sub networks that could be created.
6 networks
Question 2 – The IP address is /27. What is the first usable host address in the first usable range?
Class C
Question 2 – Class which provides the largest number of hosts per network?
Class A

13. Subnet Question
Refer to the exhibit. Which range of IP addresses would allow hosts that are connected to the Router1 Fa0/0 interface to access outside networks?
through

14. Subnet Question
Refer to the exhibit. Host A is connected to the LAN, but it cannot get access to any resources on the Internet. The configuration of the host is shown in the exhibit. What could be the cause of the problem?
The default gateway is on a different subnet from the host.

15. IP Versions IPv4 IPv6 32 bits Separated by a period 133.15.6.4
Separated by colons
More address space
Better address mgmt

16. Using Network Address Translation in a Network (NAT)
Allows a large group of private users to access the Internet by sharing a small group of public IPs
comparable to a company with a few phone lines, but many extensions
Developed to help save registered IP addresses
Provides security to PCs, servers, devices, etc

17. Advantages & Disadvantages of NAT
Reuse of IP addresses
Sharing of a global IP address
Security
Scalability
Router CPU load
Poor network performance
Remote access may be denied if trying to access a server with a private IP

18. NAT Terminology Inside local network Outside global network
any network connected to a router interface that is part of the privately addressed LAN
Outside global network
any network attached to a router that is external to the LAN

19. More NAT Terminology Inside local address Outside global address
Private IP address of a host on the local network
Must be translated to a public IP before it can travel outside
Outside global address
Actual public IP address of an external host

20. More NAT Terminology Inside global address Outside local address
IP address of inside host as it APPEARS to the outside network
Outside local address
Destination address of packet while on the local network
Usually the same as outside global address

21. Question
What must happen for a privately addressed host on an inside local network to be able to communicate with an outside destination host on the Internet?
The host IP address must be translated to an inside global address.

22. Static NAT Provides access to a local host from the Internet
Allows hosts on public network to access selected hosts on a private network
Static NAT works by mapping a specific inside local IP address to what other specific address type?
inside global

23. Static NAT Example
The host with the IP address of will always translate to

24. Dynamic NAT
Maps an unregistered IP address to a registered IP address from a group of registered IP addresses.
The host with the IP address of will translate to the first available address in the range of to

25. PAT (NAT Overload)
Many internal addresses can be translated to a single IP address using different port assignments
Each computer on the private network is translated to the same IP address ( ), but with a different port number assignment.
Outside users are unable to initiate communication to a host if using PAT

26. PAT (Overloading)
Uses unique source port numbers in the inside global IP address
Uses first available port number
PAT uses port numbers must be above 1024

27. NAT Question
Refer to the exhibit. R1 is performing NAT for the /24 inside network. HostA has sent a request to the web server. What is the destination IP address of the return packet from the web server?

28. Summary
IP addressing can be tailored to the needs of the network design through the use of custom subnet masks.
Classless subnetting gives classful IP addressing schemes more flexibility through the use of variable length subnet masks.
Network Address Translation (NAT) is a way to shield private addresses from outside users.
Port Address Translation (PAT) translates multiple local addresses to a single global IP address, maximizing the use of both private and public IP addresses.