RuggedCom RX1100, RX1000 manual Configuring PPPoE/Bridged Mode On, Adsl Fundamentals

Chapter 9 – Configuring PPPoE/Bridged Mode On ADSL

Chapter 9 – Configuring PPPoE/Bridged Mode On

ADSL

Introduction

This chapter familiarizes the user with:

∙Configuring PPPoE and Bridged Mode Links

∙Viewing status

ADSL Fundamentals

An ADSL (Asymmetric Digital Subscriber Line) line is a communications link running over regular POTS telephone service. The link is asymmetric, supporting data transfer at up to 8 Mbps from the network and up to 1 Mbps to the network. The actual bandwidth depends upon the distance between the router and telco central office, the maximum distance of which may be up to 5480 m. An ADSL card must connect to a central ADSL DSLAM for its connection.

ADSL shares ordinary telephone lines by using frequencies above the voice band. ADSL and voice frequencies will interfere with each other. If the line will be used for both data and voice, a “splitter” should be installed to divide the line for DSL and telephone.

ADSL is almost always used to make a connection to the Internet via an ISP. There are two methods for establishing the connection, PPPoe and Bridged mode.

ADSL uses the ATM protocol to communicate with the central office DSLAM. ATM uses virtual channels to route traffic and the DSL connection needs to know which virtual channels to use. Most providers use VPI=0 and VCI=35. There are exceptions to this. Some providers that use different settings are listed in the following table.

Provider	VPI	VCI
Typical Provider	0	35
Bell South	8	35
New Edge	0	38
Sprint	8	35
US West/Qwest	0	32

PPPoE/Bridged Mode Fundamentals

In PPPoE (Point-to-Point Protocol Over Ethernet) the PPP dial-up protocol is used with Ethernet over ADSL as the transport. PPPoE supports the protocol layers and authentication widely used in PPP and enables a point-to-point connection to be established in the normally multipoint architecture of Ethernet.

As your PPPoE connection is established a PPP interface will be created. The name will be “pppX” where X is the same as the interface number. Use this interface name in firewall rules.

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