User`s guide

74
Entity
Instance
Parameter
Values
Equivalent Web Parameter
apvc 0 0-255 VPI
apvc 0 0-65535 VCI
Configuration – Network > Interfaces > DSL > DSL Network Settings
This DSL PVC is using PPP 1
The default interface for DSL is PPP 1
Description
Enter a description for the DSL if required
Username
Enter ADSL Username
Password
Enter the password for the DSL account
Confirm password
Enter the password for the DSL account
Enable NAT on this interface
This parameter is used to select whether IP Network Address Translation (NAT) or Network
Address and Port Translation (NAPT) are used at the Ethernet interface. When the
parameter is set to disabled, no NAT will take place. When this parameter is enabled, extra
options described below will be displayed.
NAT and NAPT can have many uses but they are generally used to allow a number of private
IP hosts (PCs for example) to connect to the Internet through a single shared public IP
address. This has two main advantages, it saves on IP address space (the ISP only need
assign you one IP address), and it isolates the private IP hosts from the Internet, effectively
providing a simple firewall because unsolicited traffic from the Internet cannot be routed
directly to the private IP hosts.
To use NAT or NAPT correctly in the example of connecting private hosts to the Internet,
NAT or NAPT should be enabled on the router’s WAN side interface and should be disabled
on the router’s LAN side interface.
IP address
Enable standard Network Address Translation (NAT).
When a private IP host sends a UDP or TCP packet to an Internet IP address, the router
will change the source address of the packet from the private host IP to the router’s
public IP address before forwarding the packet onto the Internet host. Additionally it will
create an entry in a “NAT table” containing the private IP source address, the private IP
port number, the public IP destination address and the destination port number.
Conversely, when the router receives a reply packet back from the public host, it checks
the source IP, source port number and destination port number in the NAT table to
determine which private host to forward the packet to. Before it forwards the packet back
to the private host, it changes the destination IP address of the packet from its public IP
address to the IP address of the private host.
IP address and Port
Enable Network Address and Port Translation (NAPT).