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VCI
The valid range for the VCI is 32 to 65535. Enter the VCI
assigned to you. This field may already be configured.
ATM QoS
Select CBR (Continuous Bit Rate) to specify fixed (always-on)
bandwidth for voice or data traffic. Select UBR (Unspecified Bit
Rate) for applications that are non-time sensitive, such as e-mail.
Select VBR (Variable Bit Rate) for bursty traffic and bandwidth
sharing with other applications.
VBR is not available on all models.
Cell Rate
Cell rate configuration often helps eliminate traffic congestion
that slows transmission of real time data such as audio and video
connections.
Peak Cell Rate
(PCR)
Divide the DSL line rate (bps) by 424 (the size of an ATM cell) to
find the Peak Cell Rate (PCR). This is the maximum rate at which
the sender can send cells. Type the PCR here.
Sustain Cell
Rate (SCR)
The Sustain Cell Rate (SCR) sets the average cell rate (long-
term) that can be transmitted. Type the SCR, which must be less
than the PCR.
Maximum Burst
Size (MBS)
Maximum Burst Size (MBS) refers to the maximum number of
cells that can be sent at the peak rate. Type the MBS, which is
less than 65535.
ENCAPSULATION
Encapsulation
Select the method of encapsulation used by your ISP from the
drop-down list box.
PPPoA/PPPoE
Service Name
(PPPoE only) Type the name of your PPPoE service here.
User Name
Enter the user name exactly as your ISP assigned. If assigned a
name in the form user@domain where domain identifies a
service name, then enter both components exactly as given.
Password
A static IP address is a fixed IP that your ISP gives you. A
dynamic IP address is not fixed; the ISP assigns you a different
one each time you connect to the Internet. The Single User
Account feature can be used with either a dynamic or static IP
address.
Select Obtain an IP Address Automatically if you have a dynamic
IP address; otherwise select Static IP Address and type your ISP
assigned IP address in the IP Address field below.
Multiplex
Select the method of multiplexing used by your ISP from the
drop-down list. Choices are VC or LLC.
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Connection Settings
Always ON
Select Always ON Connection when you want your connection up
all the time. The ADSL Router will try to bring up the connection
automatically if it is disconnected.
Connect on
Demand
Connect on demand is dependent on the traffic. If there is no
traffic (or Idle) for a pre-specified period of time), the connenct
will tear down automatically. And once there is traffic send or
receive, the connection will be automatically on. Please insert the
Idle Time in minute.
IP Address
Get IP Address
The IP address can be either dynamically (via DHCP) or given IP
address provide by your ISP. For Static IP, you need to specify
the IP address, Subnet Mask and Gateway IP address.
IP Address
You must specify a Router IP address.
IP Subnet Mask
Enter a subnet mask in dotted decimal notation.
Refer to the Subnetting appendix in the to calculate a subnet
mask If you are implementing subnetting.
Gateway
You must specify a gateway IP address.
NAT
Select this option to Activate/Deactivated the NAT (Network
Address Translation) function for this VC. The NAT function can
be activated or deactivated per PVC basis.
Default Route
if enable this function, the current PVC will be the default
gateway to internet from this device.
TCP MTU
Option
RIP (Routing Information protocol) Select this option to specify
the RIP version, including RIP-1, RIP-2M and RIP-2B. RIP-2M
and RIP-2B are both sent in RIP-2 format; the difference is that
RIP-2M using Multicast and RIP-2 using Broadcast format.
Dynamic Route
RIP Direction Select this option to specify the RIP direction. None
is for disabling the RIP function. Both means the ADSL Router
will periodically send routing information and accetp routing
information then incorporate into routing table. IN only means
the ADLS router will only accept but will not send RIP packet.
OUT olny means the ADLS router will only send but will not
accept RIP packet.
Direction
IGMP (Internet Group Multicast Protocol) is a session-layer
protocol used to establish membership in a multicast group. The
ADSL ATU-R supports both IGMP version 1 (IGMP-v1) and IGMP-
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v2. Select None to disable it.
Multicast
Click Apply to save the changes.
Save
The IP address can be either dynamically (via DHCP) or given IP
address provide by your ISP. For Static IP, you need to specify
the IP address, Subnet Mask and Gateway IP address.
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6.
Network Address Translation (NAT)
This chapter discusses how to configure NAT on the WebShare Wireless N Router
ADSL2+.
6.1
NAT Overview
NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP
address of a host in a packet, for example, the source address of an outgoing
packet, used within one network to a different IP address known within another
network.
6.1.1
NAT Definitions
Inside/outside denotes where a host is located relative to the ADSL Router, for
example, the computers of your subscribers are the inside hosts, while the web
servers on the Internet are the outside hosts.
Global/local denotes the IP address of a host in a packet as the packet traverses a
router, for example, 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 in 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.
6.1.2
What NAT Does
In the simplest form, 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
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translates 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. In addition, you can designate servers, for example, a web
server and a telnet server, on your local network and make them accessible to the
outside world. With no servers defined, the ADSL Router filters 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).
6.1.3
How NAT Works
Each packet has two addresses
a source address and a destination address. For
outgoing packets, the ILA (Inside Local Address) is the source address on the LAN,
and the IGA (Inside Global Address) is the source address on the WAN. For
incoming packets, the ILA is the destination address on the LAN, and the IGA is the
destination address on the WAN. NAT maps private (local) IP addresses to globally
unique ones required for communication with hosts on other networks. It replaces
the original IP source address (and TCP or UDP source port numbers for Many-to-
One and Many-to-Many Overload NAT mapping) in each packet and then forwards it
to the Internet. The ADSL Router keeps track of the original addresses and port
numbers so incoming reply packets can have their original values restored. The
following figure illustrates this.

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