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

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

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

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

Private IP Addressing Private IP addresses assigned by IETF (Internet Engineering Task Force) reduces the number of public IP addresses assigned to organizations

Implementation of IP Addressing in the LAN SUBNETS

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

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

IP Versions IPv4 IPv6 32 bits Separated by a period 133.15.6.4 RFC 791 Separated by colons RFC 2460 More address space Better address mgmt

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

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

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

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

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

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 Example The host with the IP address of 192.168.32.10 will always translate to 213.18.123.110.

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

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

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

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.