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Logo

Uso de NAT y DHCPUso de NAT y DHCPProtocolos y Aplicaciones Parte 2Protocolos y Aplicaciones Parte 2

Fredy Campos [email protected]

Carrera Profesional de Ingeniera Electrnica y TelecomunicacionesUniversidad Nacional Tecnolgica del Cono Sur de Lima

http://www.untecs.edu.pe/portal/

ver 1.1

2012
mailto:[email protected]://www.untecs.edu.pe/portal/http://www.untecs.edu.pe/portal/http://www.untecs.edu.pe/portal/mailto:[email protected]

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AgendaAgenda

Overview

NAT Concepts

NAT Types

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ObjetivosObjetivos

Presentar el funcionamiento de NAT y aplicaciones

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AgendaAgenda

Overview

NAT Concepts

NAT Types

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Overview (1)Overview (1)Escalabilidad de InternetEscalabilidad de Internet

Limitacin de direcciones IP en IPv4 Busqueda de soluciones temporales

Network Address Translation (NAT) and Private Addressing

Allow organizations to use unregistered IP network numbers

internally and still communicate well with Internet

Classless Interdomain Routing (CIDR)

Allows ISPs to reduce the wasting of IP addresses by assigning a

company a subset of a network number rather than the entire

network.

CIDR also can allow ISPs to summarize routes such that multiple

Class A, B, or C networks match a single route, which helps

reduce the size of Internet routing tables.

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Problems with IPv4

- Shortage of IPv4 addresses

- Allocation of the last IPv4 addresses is forecasted for the year 2010

- Address classes were replaced by usage of CIDR, but this is not sufficient

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Short term solution

- NAT: Network Address Translation

Problems with IPv4




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Long term solution

- IPv6 = IPng (IP next generation)

- Provides an extended address range

Problems with IPv4




Short term solution

- NAT: Network Address Translation

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Overview (5)Overview (5)CIDRCIDR

CIDR is a global address assignment convention,defining how the Internet Assigned Numbers Authority

(IANA)

Its member agencies, and ISPs should assign the globally

unique IPv4 address space to individual organizations.

CIDR is defined in RFC 4632

Main goals (in accord to RFC 4632)

Define address assignment for aggregating (summarizing)

multiple network numbers into a single routing entity (reducing

the Internet routers routing tables) Allow ISP's to assign address ranges to their customers of sizes

other than an entire Class A, B, or C network

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Overview (6)Overview (6)CIDRCIDR

Route Aggregation for Shorter Routing Tables Ex. ISP 1 only use 198.0.0.0/8 to be reached by others

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Overview (7)Overview (7)Private AddressingPrivate Addressing

When building a private network that will have noInternet connectivity, you can use IP network numbers

called private internets

They are defined in RFC 1918, Address Allocation for

Private Internets (http://www.ietf.org/rfc/rfc1918.txt). This RFC defines a set of networks that will never be assignedto any organization as a registered network number.

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AgendaAgenda

Overview

NAT Concepts

NAT Types

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NAT Concepts (1)NAT Concepts (1)FuncionamientoFuncionamiento

Private Network

- Uses private address range (local addresses)

- Local addresses may not be used externally

Public Network

- Uses public addresses

- Public addresses are globally unique

?

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Private Network

- Uses private address range (local addresses)

- Local addresses may not be used externally

Public Network

- Uses public addresses

- Public addresses are globally unique

NAT

- Translates between local addresses and public ones

- Many private hosts share few global addresses

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Change IP Address Router change source IP Address when packet leaves the

private organization

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Ventajas Public IP Address Sharing

Hosts can share a small number of public IP addresses.

Easier Expansion

Network devices are privately addressed and a public IP address

isn't needed for each one,

Greater Local Control

Greater Flexibility In ISP Service

Increased Security

The NAT translation represents a level of indirection. Thus, itautomatically creates a type of firewall between the organization's

network and the public Internet.

(Mostly) Transparent

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Desventajas Complexity

Problems Due to Lack of Public Addresses

Compatibility Problems With Certain Applications

Problems With Security Protocols

IPSec are designed to detect modifications to headers and

commonly balk at the changes that NAT makes, since they cannot

differentiate those changes from malicious datagram hacking.

Poor Support for Client Access

Performance Reduction

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NAT Concepts (6)NAT Concepts (6)TerminologaTerminologa

NAT Address Terms Based on Device Location(Inside/Outside)

Inside Address

Any device on the organization's private network that is using NAT

is said to be on the inside network. Thus, any address that refers

to a device on the local network in any form is called an insideaddress.

Outside Address

The public internetthat is, everything outside the local network

is considered the outside network. Any address that refers to a

public Internet device is an outside address.Key Concept: In NAT, the terms inside and outside are used to identify the location of

devices. Inside addresses refer to devices on the organizations private network; outside

addresses refer to devices on the public Internet

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NAT Address Terms Based on Datagram Location(Local/Global)

Local Address

This term describes an address that appears in a datagram on the

inside network, whether it refers to an inside or outside address.

Global Address This term describes an address that appears in a datagram on the

outside network, again whether it refers to an inside or outside

address.

Key Concept: In NAT, the terms local and global are used to indicate in what network aparticular address appears. Local addresses are used on the organizations private

network (whether to refer to an inside device or an outside device); global addresses are

used on the public Internet (again, whether referring to an inside or outside device).

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Combinando los trminos Inside local address The IPv4 address that is assigned to a host on the inside network

(inside an enterprise). An inside local is the actual IP address

assigned to a host in the private enterprise network. A more

descriptive term might be inside private.

Inside global address

A legitimate IPv4 address that is assigned by ISP that represents

one or more inside local IPv4 addresses to the outside world. NAT

uses an inside global address to represent the inside host as the

packet is sent through the outside network (Internet).

A more descriptive term: inside public, so the inside global address

represents the inside host with a public IP address that can be

used for routing in the public Internet.

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Combinando los trminos (cont.) Outside global address The IPv4 address that is assigned to a host on the outside network

by the host owner. The outside global address is allocated from a

globally routable address or network space.

Outside local address

The IPv4 address of an outside host as it appears to the inside

network. Not necessarily legitimate, the outside local address is

allocated from a routable address space on the inside.

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AgendaAgenda

Overview

NAT Concepts

NAT Types

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NAT Types (1)NAT Types (1)ClasificacinClasificacin

Segn Cisco los siguientes tipos comunes pueden serusados

Static NAT

Dynamic NAT

Overloading NAT with PAT

Segn los acadmicos los tipos generales son:

Unidirectional NAT (also called outbound or traditional NAT)

Bidirectional (inbound or two-way) NAT

Port-Based or Overloaded NAT (also called NAPT or PAT)

Overlapping NAT (also called Twice NAT).

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NAT Types (2)NAT Types (2)Clasificacin comnClasificacin comn

Static NAT Maps an unregistered IPv4 address to a registered IPv4

address (one to one). Static NAT is particularly useful when a

device must be accessible from outside the network.

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Dynamic NAT Maps an unregistered IPv4 address to a registered IPv4

address from a group of registered IPv4 addresses.

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NAT Overloading Maps multiple unregistered IPv4 addresses to a single

registered IPv4 address (many to one) by using different ports.

Overloading is also known as PAT, and is a form of dynamic

NAT.

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NAT Types (5)NAT Types (5)Clasificacin acadmicaClasificacin acadmica

Unidirectional NAT (also called outbound or traditional

NAT)

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Bidirectional (inbound or two-way) NAT

NAT T ( )

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Port-Based or Overloaded NAT (also called NAPT or

PAT)

NAT T (8)NAT T (8)

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Overlapping NAT (also called Twice NAT)

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2012 | Fredy Campos | [email protected] Uso de NAT y DHCP @ F. Campos 34

Fredy Campos [email protected]

Carrera Profesional de Ingeniera Electrnica y TelecomunicacionesUniversidad Nacional Tecnolgica del Cono Sur de Lima

http://www.untecs.edu.pe/portal/
mailto:[email protected]:[email protected]://www.untecs.edu.pe/portal/http://www.untecs.edu.pe/portal/http://www.untecs.edu.pe/portal/mailto:[email protected]:[email protected]

arp_l3-2_nat-dhcp_v1.0_20120620

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