BELGACOM Forum 500 Specifications download pdf (Page 75)

Useful Information on Internet Access 73

Configuration Examples

NAT

Network address translation (NAT) is activated on accessing the

Internet (ISP). You require this feature in order to translate inter-

nal IP addresses to valid external IP addresses. This has three

important consequences for Internet access:

z Several workstations can share a single Internet access. You do

not require a LAN access, only a single account with the Inter-

net service provider.

z The IP addresses used in the LAN are translated into IP

addresses valid worldwide. So you require no such addresses

for your LAN.

z Only TCP/IP connections triggered from a workstation can be

established. Consequently, while you can call up Web pages

from a workstation, you cannot install a Web server visible in

the Internet on a workstation.

Certain protocols cannot be used when NAT is being used. This

affects protocols with the following properties:

z TCP/IP addresses are transported in the useful load,

e.g. Net-BIOS over TCP/IP.

z The protocol requires an active, inward-directed connection

establishment, e.g. ICQ.

z The protocol will function without TCP/UDP port numbers,

e.g. ICMP or IGMP.

The Forum 500 NAT has suitable processes for ensuring the func-

tions of many important protocols affected by these rules. These

are the protocols FTP (in “active” mode), CuSeeMe (“videoconfer-

encing”), IRC (“chat”), ICMP errors (“traceroute”) and ICMP echo

(“ping”).

Protocols which require inward-directed connection establishment

can be configured in the Net Configuration: Port Access menu.

For further information, refer to the online help of this menu.

1 2 ... 70 71 72 73 74 75 76 77 78 79 80 ... 143 144

No comments

BELGACOM Forum 500 Specifications Page 75