Crestron NAT Przewodnik Instalacji Pobierz pdf (Strona 6)

2-Series Feature Crestron NAT

In local area networks, a node is

any device connected to the LAN.

Transparent, in this context, signifies

that the external devices are unaware

of the address translation process.

An Internet Protocol (IP) address is a

unique 32-bit identifier for a specific

TCP/IP host computer on a network

Packets are groups of data, usually

in binary form, organized in a specific

way for transmission.

The IP NAT protocol is a router protocol that allows transparent communication

between nodes on an internal network and nodes on an external network. Since

nodes on an internal network are not assigned globally unique IP addresses,

transparent communication with an external network, without NAT, would be

impossible. This transparent communication is accomplished by modifying the IP

and protocol-specific headers of packets flowing to and from the internal network.

NAT only allows connections that are originated on the internal network, thus it

automatically provides firewall-style protection without any special set-up. It is

possible to make some internal servers available to the outside world via inbound

mapping, which maps certain well known TCP ports, such as 21 for FTP, to specific

internal addresses, making services like FTP available in a controlled way.

NOTE: Additional Ethernet and IP networking terms are defined in the Crestron

e-Control Reference Guide (D6052). The latest revision of this guide can be

obtained from the Downloads | Product Manuals | Software and Wiring Diagrams

section of the Crestron website (www. Crestron.com).

Crestron Implementation

Network Address Translation has many forms and can work in several ways. As

currently implemented for the Crestron 2-series control systems, NAT is a

combination of the Network Address Port Translator protocol (NAPT) and Bi-

Directional NAT, and solves three common problems generally experienced with

growing networks:

• shortage of globally unique IP addresses,

• firewall-like protection for the internal network, and

• flexibility of network administration.

NAT functionality is included in the firmware of Crestron 2-series control

processors, and enabled through a dual port Ethernet Z-bus expansion card.

Single IP Addressing

NAPT lets a single device, such as a router, act as an agent between the internal

network and the external network. This solves the problem of a shortage of globally

unique addresses by permitting a single, unique external IP address to represent an

entire group of computers in the internal network. Specifically, the IP address and

TCP/UDP port number of the internal node are replaced with an external IP address

and TCP/UDP port number in the IP and TCP/UDP header.

For example, suppose there was a need to remotely upload a project to five Crestron

IP enabled touchpanels residing on an internal LAN. Crestron provides a registered

port (41795) that can be accessed via the Viewport with the Remote | TCP/IP |

Connect command. From the “Crestron Viewport TCP/IP Connect” window, enter

the IP address, colon, and port number. Without NAT, five distinct IP addresses –

one for each touchpanel on the LAN – would be required, as shown below.

2 • Network Address Translator: NAT Reference Guide – DOC. 6001

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