1. © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Planning the Addressing Structure Working at a Small-to-Medium Business or ISP – Chapter 4

2. ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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. ITE PC v4.0 Chapter 1 3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public IP Addressing  IP addresses are HIERARCHIAL (like a family tree) – there are parents (networks) – there are children (hosts)

4. ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public IP Address Classes  Classes A – C – assigned to users  Class D – reserved for multicasts  Class E -- reserved for experimental use

5. ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public IP Address Classes

6. ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Private IP Addressing  Private IP addresses assigned by IETF (Internet Engineering Task Force) – reduces the number of public IP addresses assigned to organizations

7. ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Implementation of IP Addressing in the LAN SUBNETS

8. ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public IP Addressing Practice  Class C address with a default subnet mask. – Question 1 – What is the default subnet mask 255.255.255.0 – Question 2 – How many usable hosts are available? 254  IPv4 –Question 1 – Class which provides the largest number of network bits? Class C –Question 2 – Class which provides the largest number of hosts per network? Class A

9. ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public IP Addressing Practice  Class B address – Question 1 – What is the default subnet mask 255.255.0.0 – Question 2 – The IP address is 155.14.0.0 with a default subnet mask. What is the broadcast address for this network? 155.14.255.255  IPv4 –Question 1 – The IP address is 192.168.4.0 with a subnet mask of 255.255.255.224. What is the maximum number of sub networks that could be created. 6 networks –Question 2 – The IP address is 192.133.219.0/27. What is the first usable host address in the first usable range? 192.133.219.33

10. ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public IP Versions IPv4IPv6 32 bits Separated by a period 133.15.6.4 RFC 791 128 bits Separated by colons RFC 2460 More address space Better address mgmt

11. ITE PC v4.0 Chapter 1 11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

12. ITE PC v4.0 Chapter 1 12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Advantages & Disadvantages of NAT AdvantagesDisadvantages  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

13. ITE PC v4.0 Chapter 1 13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public NAT Terminology  Inside local 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

14. ITE PC v4.0 Chapter 1 14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public More NAT Terminology  Inside local 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

15. ITE PC v4.0 Chapter 1 15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public More NAT Terminology  Inside global 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

16. ITE PC v4.0 Chapter 1 16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static NAT  Provides access to a local host from the Internet  Allows hosts on public network to access selected hosts on a private network

17. ITE PC v4.0 Chapter 1 17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static NAT Example  The host with the IP address of 192.168.32.10 will always translate to 213.18.123.110.

18. ITE PC v4.0 Chapter 1 18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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 192.168.32.10 will translate to the first available address in the range of 213.18.123.10 to 213.18.123.150

19. ITE PC v4.0 Chapter 1 19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public PAT (NAT Overload)  A form of dynamic NAT that maps multiple private IP addresses to a single registered IP address by using different ports. This is known also as PAT (Port Address Translation), single address NAT or port-level multiplexed NAT.  Each computer on the private network is translated to the same IP address (213.18.123.100), but with a different port number assignment.  Outside users are unable to initiate communication to a host if using PAT

20. ITE PC v4.0 Chapter 1 20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public PAT (Overloading)  Uses unique source port numbers in the inside global IP address  Uses first available port number  These port numbers must be above 1024

21. ITE PC v4.0 Chapter 1 21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

22. ITE PC v4.0 Chapter 1 22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public