PPPoE Access Server Commands and Files

A service provider that offers DSL services or support to customers can use an access server that is running Solaris PPPoE. The PPPoE access server and client do function in the traditional client-server relationship. This relationship is similar to the relationship of the dial-out machine and dial-in server on a dial-up link. One PPPoE system initiates communications and one PPPoE system answers. By contrast, the PPP protocol has no notion of the client-server relationship. PPP considers both systems equal peers.

The commands and files that set up a PPPoE access server include the following:

• /usr/sbin/sppptun Command

• /usr/lib/inet/pppoed Daemon

• /etc/ppp/pppoe File

• /etc/ppp/pppoe.device File

• pppoe.so Shared Object

/usr/lib/inet/pppoed Daemon

The pppoed daemon accepts broadcasts for services from prospective PPPoE clients. Additionally, pppoed negotiates the server side of the PPPoE tunnel and runs pppd, the PPP daemon, over that tunnel.

You configure pppoed services in the /etc/ppp/pppoe and /etc/ppp/pppoe.device files. If /etc/ppp/pppoe exists when the system boots, pppoed runs automatically. You can also explicitly run the pppoed daemon on the command line by typing /usr/lib/inet/pppoed.

/etc/ppp/pppoe File

The /etc/ppp/pppoe file describes the services that are offered by an access server plus options that define how PPP runs over the PPPoE tunnel. You can define services for individual interfaces, or globally, that is, for all interfaces on the access server. The access server sends the information in the /etc/ppp/pppoe file in response to a broadcast from a potential PPPoE client.

The following is the basic syntax of /etc/ppp/pppoe:

global-options
service service-name
    service-specific-options
    device interface-name
  

The parameters have the following meanings.

global-options

Sets the default options for the /etc/ppp/pppoe file. These options can be any options that are available through pppoed or pppd. For complete lists of options, see the man pages pppoed(1M) and pppd(1M).

For example, you must list the Ethernet interfaces that are available for the PPPoE tunnel as part of global options. If you do not define devices in /etc/ppp/pppoe, the services are not offered on any interface.

To define devices as a global option, use the following form:

device interface <,interface>

interface specifies the interface where the service listens for potential PPPoE clients. If more than one interface is associated with the service, separate each name with a comma.

service service-name

Starts the definition of the service service-name. service-name is a string that can be any phrase that is appropriate to the services that are provided.

service-specific-options

Lists the PPPoE and PPP options specific to this service.

device interface-name

Specifies the interface where the previously listed service is available.

For additional options to /etc/ppp/pppoe, refer to the pppoed(1M) and pppd(1M) man pages.

A typical /etc/ppp/pppoe file might resemble the following.

Example 22–2 Basic /etc/ppp/pppoe File

device hme1,hme2,hme3
service internet
   pppd "name internet-server"
service intranet
   pppd "192.168.1.1:"
service debug
   device hme1
   pppd "debug name internet-server"

In this file, the following values apply.

hme1,hme2,hme3

Three interfaces on the access server to be used for PPPoE tunnels.

service internet

Advertises a service that is called internet to prospective clients. The provider that offers the service also determines how internet is defined. For example, a provider might interpret internet to mean various IP services, as well as access to the Internet.

pppd

Sets the command-line options that are used when the caller invokes pppd. The option "name internet-server" gives the name of the local machine, the access server, as internet-server.

service intranet

Advertises another service that is called intranet to prospective clients.

pppd "192.168.1.1:"

Sets the command-line options that are used when the caller invokes pppd. When the caller invokes pppd, 192.168.1.1 is set as the IP address for the local machine, the access server.

service debug

Advertises a third service, debugging, on the interfaces that are defined for PPPoE.

device hme1

Restricts debugging to PPPoE tunnels to hme1.

pppd "debug name internet-server"

Sets the command-line options that are used when the caller invokes pppd, in this instance, PPP debugging on internet-server, the local machine.

/etc/ppp/pppoe.device File

The /etc/ppp/pppoe.device file describes the services that are offered on one interface of a PPPoE access server. /etc/ppp/pppoe.device also includes options that define how PPP runs over the PPPoE tunnel. /etc/ppp/pppoe.device is an optional file, which operates exactly like the global /etc/ppp/pppoe. However, if /etc/ppp/pppoe.device is defined for an interface, its parameters have precedence for that interface over the global parameters that are defined in /etc/ppp/pppoe.

The basic syntax of /etc/ppp/pppoe.device is as follows:

service service-name
     service-specific-options
service another-service-name
      service-specific-options    

The only difference between this syntax and the syntax of /etc/ppp/pppoe is that you cannot use the device option that is shown in /etc/ppp/pppoe File.

pppoe.so Plugin

pppoe.so is the PPPoE shared object file that must be invoked by PPPoE access servers and clients. This file limits MTU and MRU to 1492, filters packets from the driver, and negotiates the PPPoE tunnel, along with pppoed. On the access server side, pppoe.so is automatically invoked by the pppd daemon.

Using PPPoE and PPP Files to Configure an Access Server

This section contains samples of all files that are used to configure an access server. The access server is multihomed. The server is attached to three subnets: green, orange, and purple. pppoed runs as root on the server, which is the default.

PPPoE clients can access the orange and purple networks through interfaces hme0 and hme1. Clients log in to the server by using the standard UNIX login. The server authenticates the clients by using PAP.

The green network is not advertised to clients. The only way clients can access green is by directly specifying “green-net” and supplying CHAP authentication credentials. Moreover, only clients joe and mary are allowed to access the green network by using static IP addresses.

Example 22–3 /etc/ppp/pppoe File for an Access Server

service orange-net
     device hme0,hme1
     pppd "require-pap login name orange-server orange-server:"
service purple-net
     device hme0,hme1 
     pppd "require-pap login name purple-server purple-server:"
service green-net
     device hme1 
     pppd "require-chap name green-server green-server:"
     nowildcard

This sample describes the services that are available from the access server. The first service section describes the services of the orange network.

service orange-net
     device hme0,hme1
     pppd "require-pap login name orange-server orange-server:"

Clients access the orange network over interfaces hme0 and hme1. The options that are given to the pppd command force the server to require PAP credentials from potential clients. The pppd options also set the server's name to orange-server, as used in the pap-secrets file.

The service section for the purple network is identical to the service section of the orange network except for the network and server names.

The next section describes the services of the green network:

service green-net
     device hme1 
     pppd "require-chap name green-server green-server:"
     nowildcard

This section restricts client access to interface hme1. Options that are given to the pppd command force the server to require CHAP credentials from prospective clients. The pppd options also set the server name to green-server, to be used in the chap-secrets file. The nowildcard option specifies that the existence of the green network is not advertised to clients.

For this access server scenario just discussed, you might set up the following /etc/ppp/options file.

Example 22–4 /etc/ppp/options File for an Access Server

 	auth
 	proxyarp
 	nodefaultroute
 	name no-service	# don't authenticate otherwise

The option name no-service overrides the server name that is normally searched for during PAP or CHAP authentication. The server's default name is the one found by the /usr/bin/hostname command. The name option in the previous example changes the server's name to no-service. The name no-service is not likely to be found in a pap or chap-secrets file. This action prevents a random user from running pppd and overriding the auth and name options that are set in /etc/ppp/options. pppd then fails because no secrets can be found for the client with a server name of no-service.

The access server scenario uses the following /etc/hosts file.

Example 22–5 /etc/hosts File for an Access Server

     172.16.0.1	orange-server
     172.17.0.1	purple-server
     172.18.0.1	green-server
     172.18.0.2	joes-pc
     172.18.0.3	marys-pc

Here is the /etc/ppp/pap-secrets file that is used for PAP authentication for clients that attempt to access the orange and purple networks.

Example 22–6 /etc/ppp/pap-secrets File for an Access Server

* orange-server "" 172.16.0.2/16+
* purple-server "" 172.17.0.2/16+

Here is the /etc/ppp/chap-secrets file that is used for CHAP authentication. Note that only clients joe and mary are listed in the file.

Example 22–7 /etc/ppp/chap-secrets File for an Access Server

 joe green-server "joe's secret" joes-pc
mary green-server "mary's secret" marys-pc