Skip to main content

1.1.2 Introducing NAT and PAT


1.1.2 Introducing NAT and PAT

 NAT is designed to conserve IP addresses and enable networks to use private IP addresses on internal networks. These private, internal addresses are translated to routable, public addresses. This is accomplished by internetwork devices running specialized NAT software which can increase network privacy by hiding internal IP addresses.
A NAT enabled device typically operates at the border of a stub network. A stub network is a network that has a single connection to its neighbor network. When a host inside the stub network wants to transmit to a host on the outside, it forwards the packet to the border gateway router. The border gateway router performs the NAT process, translating the internal private address of a host to a public, external routable address. In NAT terminology, the internal network is the set of networks that are subject to translation. The external network refers to all other addresses.
Cisco defines the following NAT terms:
  • Inside local address – The IP address assigned to a host on the inside network. The address is usually not an IP address assigned by the Internet Network Information Center (InterNIC) or service provider. This address is likely to be an RFC 1918 private address.
  • Inside global address – A legitimate IP address assigned by the InterNIC or service provider that represents one or more inside local IP addresses to the outside world.
  • Outside local address – The IP address of an outside host as it is known to the hosts on the inside network.
Outside global address – The IP address assigned to a host on the outside network. The owner of the host assigns this address.

Comments

Post a Comment

Popular posts from this blog

Windowing

Windowing 11.1.5 This page will explain how windows are used to transmit data. Data packets must be delivered to the recipient in the same order in which they were transmitted to have a reliable, connection-oriented data transfer. The protocol fails if any data packets are lost, damaged, duplicated, or received in a different order. An easy solution is to have a recipient acknowledge the receipt of each packet before the next packet is sent. If a sender had to wait for an ACK after each packet was sent, throughput would be low. Therefore, most connection-oriented, reliable protocols allow multiple packets to be sent before an ACK is received. The time interval after the sender transmits a data packet and before the sender processes any ACKs is used to transmit more data. The number of data packets the sender can transmit before it receives an ACK is known as the window size, or window. TCP uses expectational ACKs. This means that the ACK number refers to the next packet that is...
Post a Comment
Read more

OSI layers / Peer-to-peer communications / TCP/IP model

OSI layers 2.3.4 This page discusses the seven layers of the OSI model. The OSI reference model is a framework that is used to understand how information travels throughout a network. The OSI reference model explains how packets travel through the various layers to another device on a network, even if the sender and destination have different types of network media. In the OSI reference model, there are seven numbered layers, each of which illustrates a particular network function. - Dividing the network into seven layers provides the following advantages: • It breaks network communication into smaller, more manageable parts. • It standardizes network components to allow multiple vendor development and support. • It allows different types of network hardware and software to communicate with each other. • It prevents changes in one layer from affecting other layers. • It divides network communication into smaller parts to make learning it easier to understand. In the foll...
Post a Comment
Read more

1.2.2 RIP V2 Features

 1.2.2 RIP V2 Features This page will discuss RIP v2, which is an improved version of RIP v1. Both versions of RIP share the following features: It is a distance vector protocol that uses a hop count metric. It uses hold down timers to prevent routing loops – default is 180 seconds. It uses split horizon to prevent routing loops. It uses 16 hops as a metric for infinite distance. RIP v2 provides prefix routing, which allows it to send out subnet mask information with the route update. Therefore, RIP v2 supports the use of classless routing in which different subnets within the same network can use different subnet masks, as in VLSM. RIP v2 provides for authentication in its updates. A set of keys can be used on an interface as an authentication check. RIP v2 allows for a choice of the type of authentication to be used in RIP v2 packets. The choice can be either clear text or Message-Digest 5 (MD5) encryption. Clear text is the default. MD5 can be used t...
Post a Comment
Read more