AUTHOR DETAILS: CHANDRASEKHAR NAIDU MUTTINENI Mail: Blog:

Agenda for Today Types of IP Addresses – 3 minutes Introduction to NAT - 5 minutes Introduction to PAT - 5 minutes Types of Address Translations – 2 minutes Q&A – 3 minutes 2

Types of IP Addresses 3 -History of Internet Protocol addresses -4 bytes IP address in IPv4 -Max available addresses is 2^32 = 4,294,967,296 -In practice, the real limit is smaller for several reasons -IP has a network number and a host number -First Byte of IP describes the class it belongs to First byte between 1 and 126 are class A First byte between 128 and 191 are class B First byte between 192 and 223 are class C Other networks are class D and class E which is reserved - Public and Private IP addresses

Types of IP Addresses (contd.) 4 Public and Private Addresses

Introduction to NAT - Internet is growing at such a pace that IPs will soon be exhausted - Next generation IP (IPv6) will take years before the existing network infrastructure migrates to the new protocol - NAT is a method of connecting multiple computers to the Internet (or any other IP network) using one IP address - Allows to connect client networks to the Internet cheaply and efficiently 5

Introduction to PAT - NAT requires an available/free IP address every time - To overcome this, use Port Address Translation (PAT) - NAT supplemented by PAT is the most common environment - NAT gateway uses a Port Mapping Table to remember how it renumbered the ports for each client's outgoing packets 6

Types of Address Translations Nomenclature - Static NAT: Translates an Unregistered IP to a static registered IP - Dynamic NAT: Translates an unregistered IP address to a registered IP address from a group of available registered IP addresses - Overloading: unregistered IP addresses to a single registered IP address by using different ports 7

Security Considerations - Internet is not a one-way-street - Anybody can potentially access resources on your computers - NAT allows connections that are originated on the inside network - Some Internal servers can make available via Inbound Mapping - Some well known TCP Ports can be mapped to certain internal addresses (‘Static NAT’) - This is the controlled way of allowing connections 8

Notes on NAT - NAT works at Network Layer of ISO OSI reference model - Analogy: A Receptionist at an office with one public telephone number and multiple extensions. - NAT translates the IP address, Port, Checksum etc., in packet - Internet architectural documents observe that NAT is a violation of the End-to-End Principle - Port Mapping Table entry for a client times out after a defined time 9

10 Thank You. For any queries, please find contact details below: CHANDRASEKHAR NAIDU MUTTINENI Mail: Blog: