Chapter 22 Planning for PPP

Before configuring the PPP software, you need to prepare the hardware and software involved and gather some information that is needed during the configuration process. This chapter explains many of the tasks you need to perform prior to configuration, such as:

• "Determining Requirements for Your Configuration Type"

• "Determining IP Addressing for Your PPP Link"

• "Routing Considerations"

• "PPP Hardware Requirements"

• "Checklist for Configuring PPP"

The chapter concludes with a checklist to help you organize required information before you configure your PPP link (see Table 22-1).

Determining Requirements for Your Configuration Type

Solaris PPP supports many configuration options, including:

• Remote computer-to-network over a point-to-point link

• Remote computer-to-remote computer over a point-to-point link

• Network-to-network over a point-to-point link

• Dial-in server-to-multiple remote computers through one or more dynamic point-to-point links

• Dial-in server-to-multiple remote computers through a multipoint link

• Multiple remote computers comprising a virtual network, all communicating through multipoint links

These configurations are introduced in "Extending Your Network With PPP".

This section describes the information you need to gather and tasks you have to perform for each configuration type before beginning the configuration process. Read the section that describes the configuration you want to set up.

Areas you need to consider are:

• Network interface

• Addressing method

• Name service used, if any

• Dial-in as well as dial-out support

• Routing requirements

Remote Computer-to-Network Configuration

The remote computer-to-network is the most common asynchronous PPP configuration. Use it to configure machines in remote offices or users' homes that dial out over a point-to-point PPP link to a dial-in server on a network.

• Network interface - This point-to-point link uses the ipdptpn virtual network interface. You need to specify it in the configuration files of all remote machines that dial out to a network.

• Addressing method - The configuration file must include the host names or IP addresses of the machines that communicate over the link. For remote hosts, you should use existing host names and IP addresses. Refer to "Determining IP Addressing for Your PPP Link" for complete details.

• Name service - NIS and NIS+ name services are not recommended for remote hosts. These services generate a great deal of network traffic, often at unexpected times. The DNS name service is more efficient for this type of configuration. You might want to set up DNS, as described in Solaris Naming Administration Guide, on each remote host. If you don't use DNS, PPP accesses the /etc/inet/hosts file on the remote machine.

• Dial-in and dial-out support - Remote hosts usually implement dial-out communications only. They do not allow other machines to dial in to them directly. Therefore, you must update the UUCP files on each to support dial-out communications, as explained in "Editing UUCP Databases".

• Routing requirements - Because RIP is part of the Solaris TCP/IP protocol stack, it runs by default on remote hosts. Turn off RIP to improve performance, if necessary, and instead use static routing. See "Routing Protocols" and "Turning Off RIP" for details.

Remote Host-to-Remote Host Configuration

Use the host-to-host configuration to establish point-to-point communications between two remote hosts in different physical locations. This configuration is useful for two standalone machines in remote offices that need to exchange information. No physical network is involved.

• Network interface - This basic point-to-point link uses the ipdptpn virtual network interface. You must specify the interface in the configuration files of both endpoints.

• Addressing method - The configuration file must include the host names or IP addresses of the machines that can communicate over the link. Use the existing host names and the IP addresses assigned to the primary network interface, if they already exist. Otherwise, create IP addresses for the endpoints. Refer to "Determining IP Addressing for Your PPP Link" for complete details.

• Name service - Because only two peer hosts are involved, you don't need a true name service. The /etc/inet/hosts files on both peer hosts are used for address resolution.

• Dial-in and Dial-out support - Both machines need to perform dial-in and dial-out operations. You must modify the UUCP databases and /etc/passwd on both endpoints.

• Routing requirements - Because RIP is part of the Solaris TCP/IP protocol stack, it runs by default on remote hosts. Turn off RIP to improve performance, if necessary, and instead use static routing. See "Routing Protocols" and "Turning Off RIP" for details.

Network-to-Network Configuration

Use the network-to-network PPP configuration to create an internetwork joining two networks in physically separate locations. In this case, modems and PPP software function as the router connecting the networks.

• Network interface - The point-to-point link uses the ipdptpn virtual network interface. You must specify ipdptpn in the configuration files for both endpoint machines joining the two networks.

• Addressing method - The configuration file must include the host names or IP addresses of the machines that communicate over the link. Two possible addressing scenarios exist for this type of configuration; they are explained in "Determining IP Addressing for Your PPP Link".

• Name service - NIS and NIS+ name services can function over this type of PPP link; however, each network should be a separate domain. If you use DNS, both networks can be part of a single domain. Refer to Solaris Naming Administration Guide for details. If you use local files for name service, the /etc/inet/hosts files on both endpoint machines are used for address resolution. They must contain the host names and IP addresses of every host on each network that can communicate over the link.

• Dial-in and Dial-out support - Both network endpoint machines need to perform dial-in and dial-out operations, so you should update their UUCP and /etc/passwd files.

• Routing requirements - The endpoints in a network-to-network link usually run RIP in order to exchange routing information. Do not disable RIP for this configuration.

Dial-in Server With Dynamic Point-to-Point Links

A dynamic point-to-point link is one of two types of configurations that you can use for a dial-in server functioning as the network endpoint that remote hosts access. In this configuration scheme, the server connects to its remote hosts over a dynamically allocated point-to-point link. The dial-in server uses its dynamic links on an as-needed basis to establish communications with the remote hosts it serves.

• Network interface - The dynamic point-to-point link uses the ipdptp* virtual network interface with an asterisk wildcard character. The asterisk enables the link to be allocated dynamically. You must specify this interface in the configuration file.

• Addressing method - The configuration file must include the host names or IP addresses of the machines that communicate over the link. Refer to "Determining IP Addressing for Your PPP Link" for complete details.

• Name service - Although NIS and NIS+ are not recommended for remote hosts, the dial-in server in a remote host-to-network configuration can be a NIS client on the network to which it is physically connected. If NIS is on the server's physical network, make sure that the NIS maps are updated with the host names and IP addresses of the remote hosts. You can use DNS on the dial-in server and its remote hosts. For more information regarding DNS and name services in general, refer to Solaris Naming Administration Guide. If you use local files for name service, PPP access the /etc/inet/hosts file on the dial-in server for address resolution.

• Dial-in support - You must update the /etc/passwd file on the dynamic point-to-point dial-in server. The dynamic link server does not directly dial out to the remote hosts.

• Routing requirements - Because RIP is part of the Solaris TCP/IP protocol stack, it runs by default on remote hosts. Turn off RIP to improve performance, if necessary, and instead use static routing. See "Routing Protocols" and "Turning Off RIP" for details.

Multipoint Dial-in Server

A multipoint link is one of two types of configurations that you can use for a dial-in server functioning as the network endpoint that remote machines can access. In this configuration scheme, the dial-in server connects to multiple remote hosts over the same multipoint link. The remote hosts always connect to the dial-in server over a point-to-point link, as explained in "Remote Computer-to-Network Configuration".

Use this configuration when you want to define a separate network of remote hosts and their dial-in server.

• Network interface - The multipoint link uses the ipdn virtual network interface. You must specify this interface in the configuration file for the dial-in server.

• Addressing method - The configuration file must include the host names or IP addresses of the machines that communicate over the link. Refer to "Determining IP Addressing for Your PPP Link" for complete details. You must create a separate network for the machines on the multipoint link. See "Assigning a Network Number to the PPP Link" for more information.

• Name service - Although NIS and NIS+ are not recommended for remote hosts, the dial-in server in a remote host-to-network configuration can be a NIS client on the physical network to which it is connected. If NIS is on the server's physical network, make sure that the NIS maps are updated with the host names and IP addresses of the remote hosts. You can use DNS on the dial-in server and its remote hosts. For more information regarding DNS and name services in general, refer to Solaris Naming Administration Guide. If you use local files for name service, PPP uses the /etc/inet/hosts file on the dial-in server for address resolution.

• Dial-in and dial-out support - The multipoint dial-in server functions as a network router between its PPP virtual network and the physical network to which it is connected. It dials out to its remote hosts whenever it receives IP traffic from the physical network destined for its PPP network. Therefore, you must configure the multipoint dial-in server for both dial-in and dial-out support, and update its UUCP and /etc/passwd files.

• Routing requirements - The ipdn interface does not support RIP; you do not need to disable it.

Hosts on a Virtual Network

Use a virtual network configuration to connect three or more physically separated computers into a virtual network of phone lines, modems, and PPP software.

• Network interface - This type of configuration requires a multipoint link, which uses the ipdn virtual network interface. This interface connects each endpoint system with the other endpoints on the virtual network.

• Addressing method - The configuration file must include the host names or IP addresses of the machines that communicate over the link. Refer to "Determining IP Addressing for Your PPP Link" for more information. You must assign a network number to the virtual network. Refer to "Creating a Unique IP Address and Host Name" for complete details.

• Name Service - You can run NIS and NIS+ for the virtual network; however, this can affect the performance of the link. DNS is a better alternative. Refer to Solaris Naming Administration Guide for instructions on setting up these name services. If you use files for the name service, be sure to update /etc/inet/hosts on each machine with the host names and IP addresses of all machines on the virtual network.

• Dial-in and dial-out support - All machines in the virtual network must be configured for both dial-in and dial-out operations, so you should update their UUCP and /etc/passwd files.

• Routing requirements - The ipdn interface does not support RIP; you do not need to disable it.

Determining IP Addressing for Your PPP Link

To enable communications over the PPP link, the machine at one end of the link must know the host name and IP address of the peer host on the other end of the link. The PPP configurations often require a particular addressing scheme. This section explains the addressing schemes and where each should be used.

Specifying IP Addresses

On each endpoint machine, you specify addressing information in these places:

• /etc/asppp.cf configuration file

• /etc/inet/hosts file

• NIS+, NIS, or DNS databases, if applicable

When you edit the local machine's asppp.cf file, you must provide the host names and, in certain cases, the IP addresses for each endpoint machine to be on the link. For example, you must type either the IP addresses or host names for each endpoint as arguments in the ifconfig section in the configuration file:

ifconfig ipdptp0 plumb 192.99.44.01 192.99.44.02 up

See "Editing the Configuration File" for information regarding the format of /etc/asppp.cf.

Additionally, to enable communications, you must add the IP address and host name of the remote endpoints to the hosts database on the local endpoint by editing /etc/inet/hosts. This process is explained in "Configuring Network Clients".

Types of Addressing Schemes

You have a choice of several addressing schemes for PPP, depending on your configuration type. Before you edit the asppp.cf file and hosts database, you must decide on the appropriate addressing scheme for your configuration. These schemes include:

• Using the same IP addresses for the PPP endpoints as is assigned to their primary network interface in their local /etc/inet/hosts files

• Assigning a unique IP address for each PPP endpoint

• Assigning a new network number for the network created by the PPP link

Using the Same IP Address as the Primary Network Interface

This addressing scheme is appropriate for point-to-point links only. In this scheme, you specify the addresses of the primary network interface for each endpoint. (See Chapter 2, Network Services Overview for more information about the primary network interface.) These endpoints might be:

• Two standalone machines communicating over the PPP link (if they have existing IP addresses)

• Two network endpoints communicating over the PPP link

• Remote host connecting to a network dial-in server through a point-to-point link

• Dial-in server connecting to remote hosts through a dynamically allocated point-to-point link

When you edit the /etc/inet/hosts file on a local endpoint, supply the IP address of its primary network interface and host name and the IP address of the peer host on the other end of the link.

Creating a Unique IP Address and Host Name

In this method, you assign a unique host name and IP address to the PPP network interface. (You might want to call the interface hostname-ppp.) Use this addressing scheme for:

• Endpoint machines on a network used as a multipoint dial-in server.

• Machines on a virtual network.

• Remote host that uses a dedicated IP address for communicating with a dial-in server over a dynamically allocated PPP link. (Note that this is not a requirement for the dynamic link configuration.)

• Machine that is also configured as a router for a physical network, such as Ethernet or Token Ring.

• Machine in a standalone-to-standalone configuration that does not have an existing IP address. (The PPP interface becomes the primary network interface.)

You must specify the unique address and host name for the PPP network interface in the asppp.cf configuration file.

To create the new host name and IP address, add it to the /etc/inet/hosts file on the endpoint machines, as described in "hosts Database".

Assigning a Network Number to the PPP Link

You create a new network number for the PPP configuration when it involves:

• Virtual networks of computers communicating through PPP multipoint links (required)

• A multipoint dial-in server and its remote hosts (required)

• The PPP link between two networks, particularly when one or both of the network endpoint machines are also routers for a physical network (optional)

(See Chapter 5, Planning Your TCP/IP Network for information on network numbers.)

The PPP link becomes a virtual network, since it does not involve any physical network media. You need to type its network number in the networks database on all endpoint machines, along with the network numbers of the networks being linked.

The following sample shows an /etc/inet/networks file for an internetwork with PPP.

Example 22-1 /etc/inet/networks File for an Internetwork With PPP

kalahari      192.9.253
negev         192.9.201
nubian-ppp    192.29.15

In the sample file, kalahari and negev are two local area networks, and nubian-ppp is the name of the PPP link.

Routing Considerations

The RIP routing protocol runs on Solaris TCP/IP networks by default. In most cases, you should leave RIP running on point-to-point links. However, if you are having performance problems with the link, you might want to disable RIP on the point-to-point link.

RIP is not started on multipoint links. Therefore, you must set up static routing for the multipoint link. Refer to "Routing Protocols" for instructions.

For instructions on how to disable RIP, see "How to Turn Off RIP" .

PPP Hardware Requirements

The basic PPP configuration involves a computer, a modem, and RS-232 telephone lines. However, before you configure, you need to verify whether the hardware you selected can support PPP. This section describes the hardware requirements for PPP.

• Modem requirements - To run PPP, each endpoint machine must have a modem that supports at least 9600 bps or faster bidirectional connections. Such a modem implements the V.32 or V.32bis specification.

• Serial port selection (for dial-in servers only) - You can configure either serial port A or serial port B on most CPUs for PPP usage. Use the Solaris Serial Port Manager to initialize the ports on the dial-in server. System Administration Guide, Volume 1 contains instructions for selecting the appropriate port. If you have additional serial cards installed, you can also use their serial ports for PPP connections.

• Disk space - You must have 300 Kbytes of free space in /usr to install PPP.

  ---

  Note -

  You need an additional 300 Kbytes of free space in /usr to install 64-bit PPP.

  ---

Checklist for Configuring PPP

Use this checklist to prepare for configuring PPP. It lists the information you need to gather and the tasks you need to do before starting the configuration process.