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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.