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WIRELESS ROUTER ADSL
Virtual Circuit (VC): The Virtual Circuit (VC) properties of the ATM VC interface identify a unique path that your ADSL/
Ethernet router uses to communicate via the ATM-based network with the telephone company central offi ce equipment.
NAT Status: This fi led shows the current status of the NAT function for the current VC. Number of IPs: This fi eld is to
specify how many IPs are provided by your ISP for current VC. It can be single IP or multiple IPs. Note: For VCs with
single IP, they share the same DMZ & Virtual servers; for VCs with multiple IPs, each VC cab set DMZ and Virtual serv-
ers. Furthermore, for VCs with multiple IPs, they can defi ne the Address Mapping rules; for VCs with single IP, since
they have only one IP, there is no need to individually defi ne the Address Mapping rule.
6.3.1 What NAT Does
NAT changes the source IP address in a packet received from a subscriber (the inside local address) to another (the
inside global address) before forwarding the packet to the WAN side. When the response comes back, NAT trans-
lates the destination address (the inside global address) back to the inside local address before forwarding it to the
original inside host. Note that the IP address (either local or global) of an outside host is never changed. The global
IP addresses for the inside hosts can be either static or dynamically assigned by the ISP. You may also designate
servers, such as a Web server and a telnet server, on your local network and make them accessible to the out-
side world. With no servers defi ned, your ROUTER fi lters out all incoming inquiries, thus preventing intruders from
probing your network. For more information on IP address translation, refer to RFC 1631, The IP Network Address
Translator (NAT).
Inside/outside indicates where a host is located relative to the ROUTER. The computers hosts of your LAN are inside,
while the Web servers on the Internet are outside. Global/local indicates the IP address of a host in a packet as the
packet traverses a router. The local address refers to the IP address of a host when the packet is in the local network,
while the global address refers to the IP address of the host when the same packet is traveling in the WAN side.
Note that inside/outside refers to the location of a host, while global/local refers to the IP address of a host used in a
packet. Thus, an inside local address (ILA) is the IP address of an inside host of a packet when the packet is still in the
local network, while an inside global address (IGA) is the IP address of the same inside host when the packet is on the
WAN side. The following table summarizes this information.
ITEM DESCRIPTION
Inside
This refers to the host on the LAN.
Outside
This refers to the host on the WAN.
Local
This refers to the packet address (source or destination) as the packet travels on the LAN.
Global
This refers to the packet address (source or destination) as the packet travels on the WAN.
