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IGMP (Internet Group Multicast Protocol) is a network-layer protocol used to establish
membership in a Multicast group - it is not used to carry user data. IGMP version 2 (RFC 2236)
is an improvement over version 1 (RFC 1112) but IGMP version 1 is still in wide use. If you
would like to read more detailed information about interoperability between IGMP version 2
and version 1, please see sections 4 and 5 of RFC 2236. The class D IP address is used to
identify host groups and can be in the range 224.0.0.0 to 239.255.255.255. The address
224.0.0.0 is not assigned to any group and is used by IP multicast computers. The address
224.0.0.1 is used for query messages and is assigned to the permanent group of all IP hosts
(including gateways). All hosts must join the 224.0.0.1 group in order to participate in IGMP.
The address 224.0.0.2 is assigned to the multicast routers group.
The BIPAC-5100/5100W supports both IGMP version 1 (IGMP-v1) and IGMP version 2
(IGMP-v2). At start up, the BIPAC-5100/5100W queries all directly connected networks to
gather group membership. After that, the BIPAC-5100/5100W periodically updates this
information. IP multicasting can be enabled/disabled on the BIPAC-5100/5100W LAN and/or
WAN interfaces in the web configurator (LAN; WAN). Select None to disable IP multicasting on
these interfaces.
4.5 Configuring LAN
Click LAN to open the following screen.
The following table describes the labels in this screen.
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LABEL
DESCRIPTION
DHCP
If set to
Server
, your BIPAC-5100/5100W can assign IP addresses, an IP default
gateway and DNS servers to Windows 95, Windows NT and other systems that
support the DHCP client.
If set to
None
, the DHCP server will be disabled.
If set to
Relay
, the BIPAC-5100/5100W acts as a surrogate DHCP server and relays
DHCP requests and responses between the remote server and the clients. Enter the
IP address of the actual, remote DHCP server in the Remote DHCP Server field in
this case.
When DHCP is used, the following items need to be set:
LAN Subnet Mask
Enter a subnet mask in dotted decimal notation.
Client IP Pool
Starting Address
This field specifies the first of the contiguous addresses in the IP address pool.
Size of Client IP
Pool
This field specifies the size or count of the IP address pool.
Primary DNS
Server
Enter the IP addresses of the DNS servers. The DNS servers are passed to the
DHCP clients along with the IP address and the subnet mask.
Secondary DNS
Server
As above.
Remote DHCP
Server
If
Relay
is selected in the
DHCP
field above then enter the IP address of the actual
remote DHCP server here.
TCP/IP
IP Address
Enter the IP address of your BIPAC-5100/5100W in dotted decimal notation, for
example, 192.168.1.254 (factory default).
IP Subnet Mask
Type the subnet mask assigned to you by your ISP (if given).
RIP Direction
Select the RIP direction from
None
,
Both
,
In Only
and
Out Only
.
RIP Version
Select the RIP version from
RIP-1
,
RIP-2B
and
RIP-2M
.
Multicast
IGMP (Internet Group Multicast Protocol) is a session-layer protocol used to establish
membership in a multicast group. The BIPAC-5100/5100W supports both IGMP
version 1 (
IGMP-v1
) and
IGMP-v2
. Select
None
to disable it.
Apply
Click this button to save these settings back to the BIPAC-5100/5100W.
Cancel
Click this button to reset the fields in this screen.
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Chapter 5
Wireless LAN Setup
802.11b is only supported for the BIPAC-5100W
This chapter discusses how to configure Wireless LAN on the BIPAC-5100/5100W.
5.1 Wireless LAN Overview
This section introduces the wireless LAN and some basic configurations. Wireless LANs can
be as simple as two computers with wireless LAN cards communicating in a peer-to-peer
network or as complex as a number of computers with wireless LAN cards communicating
through access points which bridge network traffic to the wired LAN.
5.1.2 Channel
The range of radio frequencies used by IEEE 802.11b wireless devices is called a “channel”.
Channels available depend on your geographical area. You may have a choice of channels
(for your region) so you should use a different channel than an adjacent AP (access point) to
reduce interference. Interference occurs when radio signals from different access points
overlap causing interference and degrading performance.
Adjacent channels partially overlap however. To avoid interference due to overlap, your AP
should be on a channel at least five channels away from a channel that an adjacent AP is
using. For example, if your region has 11 channels and an adjacent AP is using channel 1,
then you need to select a channel between 6 or 11.
5.1.3 ESS ID
An Extended Service Set (ESS) is a group of access points or wireless gateways connected to
a wired LAN on the same subnet. An ESS ID uniquely identifies each set. All access points or
wireless gateways and their associated wireless stations in the same set must have the same
ESSID.
5.1.4 RTS/CTS
A hidden node occurs when two stations are within range of the same access point, but are not
within range of each other. The following figure illustrates a hidden node. Both stations (STA)
are within range of the access point (AP) or wireless gateway, but out-of-range of each other,
so they cannot “hear” each other, that is they do not know if the channel is currently being used.
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Therefore, they are considered hidden from each other.
When station A sends data to the BIPAC-5100/5100W, it might not know that the station B is
already using the channel. If these two stations send data at the same time, collisions may
occur when both sets of data arrive at the AP at the same time, resulting in a loss of messages
for both stations.
RTS/CTS is designed to prevent collisions due to hidden nodes. An RTS/CTS defines the
biggest size data frame you can send before an RTS (Request To Send)/CTS (Clear to Send)
handshake is invoked.
When a data frame exceeds the RTS/CTS value you set (between 0 to 2432 bytes), the station
that wants to transmit this frame must first send an RTS (Request To Send) message to the AP
for permission to send it. The AP then responds with a CTS (Clear to Send) message to all
other stations within its range to notify them to defer their transmission. It also reserves and
confirms with the requesting station the time frame for the requested transmission.
Stations can send frames smaller than the specified RTS/CTS directly to the AP without the
RTS (Request To Send)/CTS (Clear to Send) handshake.
You should only configure RTS/CTS if the possibility of hidden nodes exists on your network
and the “cost” of resending large frames is more than the extra network overhead involved in
the RTS (Request To Send)/CTS (Clear to Send) handshake.
If the RTS/CTS value is greater than the Fragmentation Threshold value (see next), then the
RTS (Request To Send)/CTS (Clear to Send) handshake will never occur as data frames will
be fragmented before they reach RTS/CTS size.
5.1.5 Fragmentation Threshold
A Fragmentation Threshold is the maximum data fragment size (between 256 and 2432 bytes)
that can be sent in the wireless network before the BIPAC-5100/5100W will fragment the
packet into smaller data frames.
A large Fragmentation Threshold is recommended for networks not prone to interference while
you should set a smaller threshold for busy networks or networks that are prone to
interference.
If the Fragmentation Threshold value is smaller than the RTS/CTS value (see previously) you
set then the RTS (Request To Send)/CTS (Clear to Send) handshake will never occur as data
frames will be fragmented before they reach RTS/CTS size.
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5.2 Levels of Security
Wireless security is vital to your network to protect wireless communication between wireless
stations, access points and the wired network.
The figure below shows the possible wireless security levels on your BIPAC-5100/5100W. The
highest security level relies on EAP (Extensible Authentication Protocol) for authentication and
utilizes dynamic WEP key exchange. It requires interaction with a RADIUS (Remote
Authentication Dial-In User Service) server either on the WAN or your LAN to provide
authentication service for wireless stations.
If you do not enable any wireless security on your BIPAC-5100/5100W, your network is
accessible to any wireless networking device that is within range.
Use the BIPAC-5100/5100W web configurator to configurator to set up your wireless LAN
security settings. Refer to the chapter on using the BIPAC-5100/5100W web configurator to
see how to access the web configurator.
5.3 Data Encryption with WEP
WEP encryption scrambles the data transmitted between the wireless stations and the access
points to keep network communications private. It encrypts unicast and multicast
communications in a network. Both the wireless stations and the access points must use the
same WEP key for data encryption and decryption.
Your BIPAC-5100/5100W allows you to configure up to four 64-bit or 128-bit WEP keys but
only one key can be enabled at any one time.
5.4 Configuring Wireless LAN
Click Wireless LAN, Wireless to open the Wireless screen.

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