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NAT (4. IPS)

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NAT & IPsec

NAT traversal. How Does NAT-T work with IPSec? Introduction: This document describes details on how NAT-T works.

How Does NAT-T work with IPSec?

Background: ESP encrypts all critical information, encapsulating the entire inner TCP/UDP datagram within an ESP header. ESP is an IP protocol in the same sense that TCP and UDP are IP protocols (OSI Network Layer 3), but it does not have any port information like TCP/UDP (OSI Transport Layer 4). Routing (Networking - engineering) Carrier-grade NAT. Carrier-grade NAT (CGN), also known as large-scale NAT (LSN), is an approach to IPv4 network design in which end sites, in particular residential networks, are configured with private network addresses that are translated to public IPv4 addresses by middlebox network address translator devices embedded in the network operator's network, permitting the sharing of small pools of public addresses among many end sites.

Carrier-grade NAT

This shifts the NAT function and configuration thereof from the customer premises to the Internet service provider network. Carrier-grade NAT has been proposed as an approach for mitigating IPv4 address exhaustion.[1] Critics of carrier-grade NAT argue the following aspects: One use scenario of CGN can be described as NAT444,[3] because some customer's connections to public servers would pass through three different IPv4 addressing domains: the customer's own private network, the carrier's private network and the public Internet.

Traversal Using Relays around NAT. TURN is specified by RFC 5766.

Traversal Using Relays around NAT

An update to TURN for IPv6 is specified in RFC 6156. The TURN URI scheme is documented in RFC 7065. Introduction[edit] NATs, while providing many benefits, also come with many drawbacks. The most troublesome of those drawbacks is the fact that they break many existing IP applications, and make it difficult to deploy new ones. Session Traversal Utilities for NAT (STUN) provides one means for an application to traverse a NAT. A complete solution requires a means by which a client can obtain a transport address from which it can receive media from any peer which can send packets to the public Internet. Although TURN will almost always provide connectivity to a client, it comes at high cost to the provider of the TURN server. Protocol[edit] The process begins when a Client Computer ("Client") wants to contact a Peer Computer ("Peer") for a data transaction, but cannot do so due to both, Client and Peer, being behind respective NATs.

See also[edit] [ScreenOS] NAT Traversal overview. This article provides an overview of NAT Transversal.

[ScreenOS] NAT Traversal overview

An overview of NAT Transversal. Note: This article is applicable to Screen OS 5.0 or later; however, NAT-T draft 2 is not supported, until Screen OS 5.1. Traditionally, IPSec does not work when traversing across a device doing NAT. [ScreenOS] NAT Traversal overview. IP NAT Address Terminology. IP NAT Address Terminology(Page 2 of 3) Combining Inside/Outside and Local/Global Address Designations This is a bit confusing, so I will try to explain further.

IP NAT Address Terminology

The NAT translating router has the job of interfacing the inside network to the outside network (the Internet). Inside devices need to be able to talk to outside devices and vice-versa, but inside devices can only use addressing consistent with the local network addressing scheme. Similarly, outside devices cannot use local addressing. Inside Local Address: An address of a device on the local network, expressed using its normal local device representation. Let's say that device wants to send an HTTP request to an Internet server located at address Outside Global Address: An address of an external (public Internet) device as it is referred to on the global Internet. Phew, it's still confusing, isn't it? Home - Table Of Contents - Contact Us. Network Address Translation.

Network Address Translation, defined by RFC 1631, is becoming very popular in today's networks as it's supported by almost every operating system, firewall appliance and application.

Network Address Translation

NAT was born thanks to the fast depletion of public IP Addresses, in other words real IP Addresses that can only exist on the Internet. As IP Addresses are 32 Bit, in theory we could have upto 4,294,967,296 IP Addresses (that's 2^32) ! In practice though the number is a lot smaller, somewhere around 3.2 billion, because of the way the IP Addresses are separated into Classes (Class A, B , C e.t.c) and the need to set aside special addresses for multicasting (also known as Class D), broadcasting and other functions.

This exciting section will show, and explain in detail, what NAT is, its different modes and how they work. Network Address Translation (NAT) FAQ. NAT: Local and Global Definitions. Introduction This document defines and clarifies the Network Address Translation (NAT) terms of inside local, inside global, outside local, and outside global.

NAT: Local and Global Definitions

Prerequisites Requirements There are no specific requirements for this document. Components Used This document is not restricted to specific software and hardware versions. Network Address Translation (NAT) FAQ. Configuring NAT Overload On A Cisco Router. NAT w/ IPTABLES. 4. IPS Transport Layer.