Concepts and Principles of Operation
packets are to be filtered or forwarded. If no access list is specified, all valid packets will be forwarded. You can specify in the IP access list the following criteria: source IP address, destination IP address, source port number, destination port number, and the protocol which when matched will be forwarded or filtered.
NAT
The ISP generally offers two type of accounts to SOHO users. The Single User account, and the LAN Access (Multiple Users) account. The Single User account is often referred as Terminal Adapter or Modem account where single user Internet access is assumed. The LAN Access account cost more than the Single User account because multiple IP addresses are assigned. Network Translation (NAT) is designed to allow multiple users on the LAN to access Internet simultaneously using the Single User account. In addition to cost saving, NAT is also useful in areas in which security or convenience are a concern. It is convenient in the sense that, the users don’t have to change the private legacy IP addressed already in use.
In order for the outside world to access the TCP/IP servers on the LAN, the Hypertec Router allows a list of internal IP addresses to be associated with FTP, Telnet, HTTP, and Email servers. Traffic destined for the list servers are forwarded to the specified IP addresses. The inbound traffic distribution works only for static IP address arrangement where you can register an IP address against the domain names. You will not have an IP address to register or publish when access to the Internet is via a
There are some limitation on the NAT application :
1.If the ISDN connection drops (e.g., because of an idle
2.Certain applications, like some
instead of the "correct" dynamically assigned address. The remote application while sending UDP packets toward the private IP address will not be able to deliver.
3.
NAT is available for Internet connections only. The Intranet connection is not affected by the Internet NAT setting.
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