Chapter 11. PPPoE

Table of Contents

The FB2500 can operate as a PPPoE client. This is typically used to connect to an Internet service provider, either via a suitable PPPoE modem, bridging router, or direct connection.

The typical usage is to use one or more ports on the FB2500 each connected directly to a suitable PPPoE device such as a bridging router.

The PPPoE device is usually very dumb and may not need any configuration at all. The FireBrick is responsible for the login to the ISP using the PPPoE link, and the configuration for this is part of the FB2500's configuration and not the router. This makes it very easy to make use of spare routers, etc, without the complication of configuring additional devices.

It is possible to connect more than one PPP device to a single FB2500 port using an Ethernet switch. If you do this then you ideally need a switch that handles VLANs (see Appendix E if you are not familiar with VLANs) so that each router can be logically connected to a different interface on the FireBrick. It is also a good idea to have a switch that supports jumbo frames where the endpoint supports them (FTTC, FTTP, and via suitable modems BT 21CN and TalkTalk).

Note

This section contains information relating to access network services (such as DSL and Fibre-To-The-Cabinet) available in the United Kingdom. Although this information will not be directly applicable to services available in other countries, the concepts are the same - with appropriate knowledge of your ISP service, and suitable equipment, the FB2500 should work equally well with services that are available in other countries.

11.1. Types of DSL line and router in the United Kingdom

In the UK there are various types of DSL line and router than can be used. Any device that supports PPPoE can work with the FireBrick, but some options are only available with some devices, as listed below :-

BT 20CN or 21CN lines can support PPPoE and PPPoA on the wire. This means you can use them with a PPPoE/A modem (such as a Vigor V-120) out of the box, or with a bridging router such as the Zyxel P660 configured in bridge mode. BT support baby jumbo frames too.
Other carrier PPPoA lines only support PPPoA, in theory. In practice they also support PPPoE. This means you can use a PPPoE/A modem, or a bridging modem.
TalkTalk lines support both PPPoA and PPPoE, and so can work with a bridging modem. They support baby jumbo frames too.
BT FTTC lines come with a VDSL modem which supports PPPoE directly so no extra equipment is needed to connect to the FireBrick.
BT FTTP lines terminate on an active NTE which supports PPPoE directly so no extra equipment is needed to connect to the FireBrick.

For other types of lines in the UK, or those in other countries, you need to know what they can do on the wire (PPPoA or PPPoE) and have a suitable modem/router to talk that protocol and convert to PPPoE on the LAN link to the FB2500. It seems most DSL routers will bridge PPPoE on the wire to PPPoE on the LAN, but few will act as a PPPoE access concentrator. The Vigor V-120 is one of the few that handle PPPoA on the wire and PPPoE link to the FB2500.

A significant benefit of the Vigor V-120 is that it works with no configuration on BT 20CN and 21CN lines as well as other carrier PPPoA lines and TalkTalk lines - you just plug it in to the line and the FB2500 and it just works. There are also modems that work in bridged mode, and support baby jumbo frames allowing PPPoE through to the carrier BRAS with full size MTU.

For fibre to the cabinet (FTTC) and fibre to the premises (FTTP) service you connect the FB2500 directly to the service (BT supplied modem) with no extra equipment.


10.3. Basic principles		11.2. Definining PPPoE links