PPP(8)

NAME
ppp - Point to Point Protocol (aka iijppp)

SYNOPSIS
ppp [-auto | -background | -ddial | -direct | -dedicated] [-alias] [system]

DESCRIPTION
This is a user process PPP software package. Normally, PPP is implemented as a part of the kernel (e.g. as managed by pppd) and it's thus somewhat hard to debug and/or modify its behavior. However, in this implementation PPP is done as a user process with the help of the tunnel device driver (tun).

Major Features

Provides interactive user interface. Using its command mode, the user can easily enter commands to establish the connection with the remote end, check the status of connection and close the connection. All functions can also be optionally password protected for security.

Supports both manual and automatic dialing. Interactive mode has a “term” command which enables you to talk to your modem directly. When your modem is connected to the remote peer and it starts to talk PPP , the PPP software detects it and switches to packet mode automatically. Once you have determined the proper sequence for connecting with the remote host, you can write a chat script to define the necessary dialing and login procedure for later convenience.

Supports on-demand dialup capability. By using auto mode, ppp will act as a daemon and wait for a packet to be sent over the PPP link. When this happens, the daemon automatically dials and establishes the connection. In almost the same manner ddial mode (dedicated or daemon dialing) also automatically dials and establishes the connection. However, it differs in that it will dial the remote site any time it detects the link is down, even if there are no packets to be sent. This mode is useful for full-time connections who worry less about line charges and more about being connected full time.

Supports packet aliasing. Packet aliasing, more commonly known as masquerading, allows computers on a private, unregistered network to access the internet. The PPP host acts as a masquerading gateway. IP addresses as well as TCP and UDP port numbers are aliased for outgoing packets and de-aliased for returning packets.

Supports background PPP connections. In background mode, if ppp successfully establishes the connection, it will become a daemon. Otherwise, it will exit with an error.

Supports server-side PPP connections. In direct mode, acts as server which accepts incoming PPP connections on stdin/stdout.

Supports PAP and CHAP authentication.

Supports Proxy Arp. When PPP is set up as server, you can also configure it to do proxy arp for your connection.

Supports packet filtering. User can define four kinds of filters: ifilter for incoming packets, ofilter for outgoing packets, dfilter to define a dialing trigger packet and afilter for keeping a connection alive with the trigger packet.

Tunnel driver supports bpf. The user can use tcpdump(1) to check the packet flow over the PPP link.

Supports PPP over TCP capability.

Supports IETF draft Predictor-1 compression. ppp supports not only VJ-compression but also Predictor-1 compression. Normally, a modem has built-in compression (e.g. v42.bis) and the system may receive higher data rates from it as a result of such compression. While this is generally a good thing in most other situations, this higher speed data imposes a penalty on the system by increasing the number of serial interrupts the system has to process in talking to the modem and also increases latency. Unlike VJ-compression, Predictor-1 compression pre-compresses all data flowing through the link, thus reducing overhead to a minimum.

Supports Microsofts IPCP extentions. Name Server Addresses and NetBIOS Name Server Addresses can be negotiated with clients using the Microsoft PPP stack (ie. Win95, WinNT)

GETTING STARTED
When you first run ppp you may need to deal with some initial configuration details. First, your kernel should include a tunnel device (the default in FreeBSD 2.0.5 and later). If it doesn't, or if you require more than one tun interface, you'll need to rebuild your kernel with the following line in your kernel configuration file:
    pseudo-device tun N
where N is the maximum number of PPP connections you wish to support. Second, check your /dev directory for the tunnel device entries /dev/tunN, where N represents the number of the tun device, starting at zero. If they don't exist, you can create them by running "sh ./MAKEDEV tunN". This will create tun devices 0 through N. Last of all, create a log file. Ppp uses syslog(3) to log information. A common log file name is /var/log/ppp.log. To make output go to this file, put the following lines in the /etc/syslog.conf file:
    !ppp
    *.* /var/log/ppp.log
It is possible to have more than one ppp log file by creating a link to the ppp executable:
    # cd /usr/sbin
    # ln ppp ppp0
and using
    !ppp0
    *.* /var/log/ppp0.log
in /etc/syslog.conf. Don't forget to send a HUP signal to syslogd after altering /etc/syslog.conf.

MANUAL DIALING
In the following examples, we assume that your machine name is awfulhak. If you set your hostname and password in /etc/ppp/ppp.secret, you can't do anything except run the help, passwd and quit commands.

    ppp on "your hostname"> help
     help    : Display this message
     passwd  : Password for security
     quit    : Quit the PPP program
    ppp on awfulhak> pass <password>

The "on" part of your prompt will change to "ON" if you specify the correct password.

    ppp ON awfulhak>

You can now specify the device name, speed and parity for your modem, and whether CTS/RTS signalling should be used (CTS/RTS is used by default). If your hardware does not provide CTS/RTS lines (as may happen when you are connected directly to certain ppp-capable terminal servers), ppp will never send any output through the port; it waits for a signal which never comes. Thus, if you have a direct line and can't seem to make a connection, try turning ctsrts off:

    ppp ON awfulhak> set line /dev/cuaa0
    ppp ON awfulhak> set speed 38400
    ppp ON awfulhak> set parity even
    ppp ON awfulhak> set ctsrts on
    ppp ON awfulhak> show modem
    * Modem related information is shown here *
    ppp ON awfulhak>

The term command can now be used to talk directly with your modem:

    ppp ON awfulhak> term
    at
    OK
    atdt123456
    CONNECT
    login: ppp
    Password:
    Protocol: ppp

When the peer starts to talk in PPP, ppp detects this automatically and returns to command mode.

    ppp ON awfulhak>
    PPP ON awfulhak>

You are now connected! Note that ‘PPP’ in the prompt has changed to capital letters to indicate that you have a peer connection. The show command can be used to see how things are going:

    PPP ON awfulhak> show lcp
    * LCP related information is shown here *
    PPP ON awfulhak> show ipcp
    * IPCP related information is shown here *

At this point, your machine has a host route to the peer. This means that you can only make a connection with the host on the other side of the link. If you want to add a default route entry (telling your machine to send all packets without another routing entry to the other side of the ppp link), enter the following command:

    PPP ON awfulhak> add 0 0 HISADDR

The string ‘HISADDR’ represents the IP address of the connected peer. This variable is only available once a connection has been established. A common error is to specify the above command in your ppp.conf file. This won't work as the remote IP address hasn't been established when this file is read. You can now use your network applications (ping, telnet, ftp etc.) in other windows on your machine. Refer to the PPP COMMAND LIST section for details on all available commands.

AUTOMATIC DIALING
To use automatic dialing, you must prepare some Dial and Login chat scripts. See the example definitions in /etc/ppp/ppp.conf.sample (the format of ppp.conf is pretty simple).
•   Each line contains one command, label or comment.
•   A line starting with a ‘#’ character is treated as a comment line.
•   A label name starts in the first column and is followed by a colon (:).
•   A command line must contain a space or tab in the first column.
The ppp.conf file should consist of at least a “default” section. This section is always executed. It should also contain one or more sections, named according to their purpose, for example, “MyISP” would represent your ISP, and “ppp-in” would represent an incoming ppp configuration. You can now specify the destination label name when you invoke ppp. Commands associated with the “default” label are executed, followed by those associated with the destination label provided. When ppp is started with no arguments, the “default” section is still executed. The load command can be used to manually load a section from the ppp.conf file:

    PPP ON awfulhak> load MyISP

Once the connection is made, the ppp portion of the prompt will change to PPP:

    # ppp MyISP
    ppp ON awfulhak> dial
    dial OK!
    login OK!
    PPP ON awfulhak>

If the /etc/ppp/ppp.linkup file is available, its contents are executed when the PPP connection is established. See the provided “pmdemand” example in /etc/ppp/ppp.conf.sample which adds a default route. The string HISADDR is available as the IP address of the remote peer. Similarly, when a connection is closed, the contents of the /etc/ppp/ppp.linkdown file are executed.

BACKGROUND DIALING
If you want to establish a connection using ppp non-interactively (such as from a crontab(5) entry or an at(1) job) you should use the -background option. You must also specify the destination label in /etc/ppp/ppp.conf to use. This label must contain the “set ifaddr” command to define the remote peer's IP address. (refer to /etc/ppp/ppp.conf.sample) When -background is specified, ppp attempts to establish the connection immediately. If multiple phone numbers are specified, each phone number will be tried once. If the attempt fails, ppp exits immediately with a non-zero exit code. If it succeeds, then ppp becomes a daemon, and returns an exit status of zero to its caller. The daemon exits automatically if the connection is dropped by the remote system, or it receives a TERM signal.

DIAL ON DEMAND
Demand dialing is enabled with the -auto or -ddial options. You must also specify the destination label in /etc/ppp/ppp.conf to use. It must contain the “set ifaddr” command to define the remote peer's IP address. (refer to /etc/ppp/ppp.conf.sample)

    # ppp -auto pmdemand
    #

When -auto or -ddial is specified, ppp runs as a daemon but you can still configure or examine its configuration by using the diagnostic port as follows (this can be done in -background and -direct mode too):

    # telnet localhost 3000
    Trying 127.0.0.1...
    Connected to awfulhak.
    Escape character is '^]'.
    PPP on awfulhak> pass xxxx
    PPP ON awfulhak> show ipcp
    IPCP [OPEND]
      his side: xxxx
      ....

Each ppp daemon has an associated port number which is computed as "3000 + tunnel_device_number". In -auto mode, when an outgoing packet is detected, ppp will perform the dialing action (chat script) and try to connect with the peer. In -ddial mode, the dialing action is performed any time the line is found to be down. If the connect fails, the default behavior is to wait 30 seconds and then attempt to connect when another outgoing packet is detected. This behavior can be changed with

    set redial seconds|random[.nseconds|random] [dial_attempts]

‘Seconds’ is the number of seconds to wait before attempting to connect again. If the argument is ‘random’, the delay period is a random value between 0 and 30 seconds. ‘Nseconds’ is the number of seconds to wait before attempting to dial the next number in a list of numbers (see the “set phone” command). The default is 3 seconds. Again, if the argument is ‘random’, the delay period is a random value between 0 and 30 seconds. ‘dial_attempts’ is the number of times to try to connect for each outgoing packet that is received. The previous value is unchanged if this parameter is omitted. If a value of zero is specified for ‘dial_attempts’, ppp will keep trying until a connection is made.

    set redial 10.3 4

will attempt to connect 4 times for each outgoing packet that is detected with a 3 second delay between each number and a 10 second delay after all numbers have been tried. If multiple phone numbers are specified, the total number of attempts is still 4 (it does not attempt each number 4 times). Modifying the dial delay is very useful when running ppp in demand dial mode on both ends of the link. If each end has the same timeout, both ends wind up calling each other at the same time if the link drops and both ends have packets queued. At some locations, the serial link may not be reliable, and carrier may be lost at inappropriate times. It is possible to have ppp redial should carrier be unexpectedly lost during a session.

    set reconnect timeout ntries

This command tells ppp to re-establish the connection ntries times on loss of carrier with a pause of timeout seconds before each try. For example,

    set reconnect 3 5

tells ppp that on an unexpected loss of carrier, it should wait 3 seconds before attempting to reconnect. This may happen up to 5 times before ppp gives up. The default value of ntries is zero (no reconnect). Care should be taken with this option. If the local timeout is slightly longer than the remote timeout, the reconnect feature will always be triggered (up to the given number of times) after the remote side times out and hangs up. NOTE: In this context, losing too many LQRs constitutes a loss of carrier and will trigger a reconnect. If the -background flag is specified, all phone numbers are dialed at most once until a connection is made. The next number redial period specified with the “set redial” command is honoured, as is the reconnect tries value. If your redial value is less than the number of phone numbers specified, not all the specified numbers will be tried. To terminate the program, type PPP ON awfulhak> close ppp ON awfulhak> quit all

A simple “quit” command will terminate the telnet connection but not the program itself. You must use “quit all” to terminate the program as well.

RECEIVING INCOMING PPP CONNECTIONS (Method 1)
To handle an incoming PPP connection request, follow these steps:

1.  Make sure the modem and (optionally) /etc/rc.serial is configured correctly.
    •   Use Hardware Handshake (CTS/RTS) for flow control.
    •   Modem should be set to NO echo back (ATE0) and NO results string (ATQ1).

2.  Edit /etc/ttys to enable a getty on the port where the modem is attached. For example:
        ttyd1 /usr/libexec/getty std.38400 dialup on secure
    Don't forget to send a HUP signal to the init process to start the getty.
        # kill -HUP 1

3.  Prepare an account for the incoming user.

        ppp:xxxx:66:66:PPP Login User:/home/ppp:/usr/local/bin/ppplogin

4.  Create a /usr/local/bin/ppplogin file with the following contents:

        #!/bin/sh -p
        exec /usr/sbin/ppp -direct

    (You can specify a label name for further control.)

    Direct mode ( -direct ) lets ppp work with stdin and stdout. You can also telnet to port 3000 plus the current tunnel device number to get command mode control in the same manner as client-side

5.  Optional support for Microsoft's IPCP Name Server and NetBIOS Name Server negotiation can be enabled use “enable msext” and “set ns pri-addr [sec-addr]” along with “set nbns pri-addr [sec-addr]” in your ppp.conf file

RECEIVING INCOMING PPP CONNECTIONS (Method 2)
This method differs in that it recommends the use of mgetty+sendfax to handle the modem connections. The latest version 0.99 can be compiled with the “AUTO_PPP” option to allow detection of clients speaking PPP to the login prompt. Follow these steps:

1.  Get, configure, and install mgetty+sendfax v0.99 or later making sure you have used the AUTO_PPP option.

2.  Edit /etc/ttys to enable a mgetty on the port where the modem is attached. For example:
        cuaa1 /usr/local/sbin/mgetty -s 57600 dialup on

3.  Prepare an account for the incoming user.

        Pfred:xxxx:66:66:Fred's PPP:/home/ppp:/etc/ppp/ppp-dialup

4.  Examine the files /etc/ppp/sample.ppp-dialup /etc/ppp/sample.ppp-pap-dialup and /etc/ppp/ppp.conf.sample for ideas. ppp-pap-dialup is supposed to be called from /usr/local/etc/mgetty+sendfax/login.conf from a line like
        /AutoPPP/ - - /etc/ppp/ppp-pap-dialup

PPP OVER TCP (a.k.a Tunneling)
Instead of running ppp over a serial link, it is possible to use a tcp connection instead by specifying a host and port as the device:
    set device ui-gate:6669
Instead of opening a serial device, ppp will open a tcp connection to the given machine on the given socket. It should be noted however that ppp doesn't use the telnet protocol and will be unable to negotiate with a telnet server. You should set up a port for receiving this ppp connection on the receiving machine (ui-gate). This is done by first updating /etc/services to name the service:
    ppp-in 6669/tcp # Incoming ppp connections over tcp
and updating /etc/inetd.conf to tell inetd how to deal with incoming connections on that port:
    ppp-in stream tcp nowait root /usr/sbin/ppp ppp -direct ppp-in
Don't forget to send a HUP signal to inetd after you've updated /etc/inetd.conf. Here, we use a label named “ppp-in”. The entry in /etc/ppp/ppp.conf on ui-gate (the receiver) should contain the following:

    ppp-in:
     set timeout 0
     set ifaddr 10.0.4.1 10.0.4.2
     add 10.0.4.1 255.255.255.255 127.0.0.1
     add 10.0.1.0 255.255.255.0 10.0.4.1

You may also want to enable PAP or CHAP for security. The entry in /etc/ppp/ppp.conf on awfulhak (the initiator) should contain the following:

    ui-gate:
     set escape 0xff
     set device ui-gate:ppp-in
     set dial
     set timeout 30 5 4
     set log Phase Chat Connect Carrier hdlc LCP tun
     set ifaddr 10.0.4.2 10.0.4.1
     add 10.0.4.2 255.255.255.255 127.0.0.1
     add 10.0.2.0 255.255.255.0 10.0.4.2

We're assigning the address of 10.0.4.1 to ui-gate, and the address 10.0.4.2 to awfulhak. To open the connection, just type
    awfulhak # ppp -background ui-gate
The result will be an additional "route" on awfulhak to the 10.0.2.0/24 network via the tcp connection, and an additional "route" on ui-gate to the 10.0.1.0/24 network. The networks are effectively bridged - the underlying tcp connection may be across a public network (such as the Internet), and the ppp traffic is conceptually encapsulated (although not packet by packet) inside the tcp stream between the two gateways. The major disadvantage of this mechanism is that there are two "guaranteed delivery" mechanisms in place - the underlying tcp stream and whatever protocol is used over the ppp link - probably tcp again. If packets are lost, both levels will get in eachothers way trying to negotiate sending of the missing packet.

PACKET ALIASING
The -alias command line option enables packet aliasing. This allows the ppp host to act as a masquerading gateway for other computers over a local area network. Outgoing IP packets are aliased so that they appear to come from the ppp host, and incoming packets are de-aliased so that they are routed to the correct machine on the local area network. Packet aliasing allows computers on private, unregistered subnets to have internet access, although they are invisible from the outside world. In general, correct ppp operation should first be verified with packet aliasing disabled. Then, the -alias option should be switched on, and network applications (web browser, telnet, ftp, ping, traceroute) should be checked on the ppp host. Finally, the same or similar applications should be checked on other computers in the LAN. If network applications work correctly on the ppp host, but not on other machines in the LAN, then the masquerading software is working properly, but the host is either not forwarding or possibly receiving IP packets. Check that IP forwarding is enabled in /etc/rc.conf and that other machines have designated the ppp host as the gateway for the LAN.

PACKET FILTERING
This implementation supports packet filtering. There are four kinds of filters; ifilter, ofilter, dfilter and afilter. Here are the basics:
•   A filter definition has the following syntax: set filter-name rule-no action [src_addr/src_width] [dst_addr/dst_width] [proto [src [lt|eq|gt] port ]] [dst [lt|eq|gt] port] [estab]

    1.  ‘filter-name’ should be one of ifilter, ofilter, dfilter or afilter.

    2.  There are two actions: ‘permit’ and ‘deny’. If a given packet matches the rule, the associated action is taken immediately.

    3.  ‘src_width’ and ‘dst_width’ work like a netmask to represent an address range.

    4.  ‘proto’ must be one of icmp, udp or tcp.

    5.  ‘port number’ can be specified by number and service name from /etc/services.
•   Each filter can hold up to 20 rules, starting from rule 0. The entire rule set is not effective until rule 0 is defined, ie. the default is to allow everything through.
•   If no rule is matched to a packet, that packet will be discarded (blocked).
•   Use “set filter-name -1” to flush all rules.
See /etc/ppp/ppp.conf.filter.example.

SETTING IDLE, LINE QUALITY REQUEST, RETRY TIMER
To check/set idletimer, use the “show timeout” and “set timeout [lqrtimer [retrytimer]]” commands:

    ppp ON awfulhak> set timeout 600

The timeout period is measured in seconds, the default values for which are timeout = 180 or 3 min, lqrtimer = 30sec and retrytimer = 3sec. To disable the idle timer function, use the command

    ppp ON awfulhak> set timeout 0

In -auto mode, an idle timeout causes the PPP session to be closed, though the ppp program itself remains running. Another trigger packet will cause it to attempt to reestablish the link.

PREDICTOR-1 COMPRESSION
This version supports CCP and Predictor type 1 compression based on the current IETF-draft specs. As a default behavior, ppp will attempt to use (or be willing to accept) this capability when the peer agrees (or requests it). To disable CCP/predictor functionality completely, use the “disable pred1” and “deny pred1” commands.

CONTROLLING IP ADDRESS
ppp uses IPCP to negotiate IP addresses. Each side of the connection specifies the IP address that it's willing to use, and if the requested IP address is acceptable then ppp returns ACK to the requester. Otherwise, ppp returns NAK to suggest that the peer use a different IP address. When both sides of the connection agree to accept the received request (and send ACK), IPCP is set to the open state and a network level connection is established. To control this IPCP behavior, this implementation has the “set ifaddr” command for defining the local and remote IP address: set ifaddr [src_addr [dst_addr [netmask]]] Where, ‘src_addr’ is the IP address that the local side is willing to use and ‘dst_addr’ is the IP address which the remote side should use. ‘netmask’ is interface netmask.

    set ifaddr 192.244.177.38 192.244.177.2 255.255.255.0

The above specification means:
•   I strongly want to use 192.244.177.38 as my IP address, and I'll disagree if the peer suggests that I use another address.
•   I strongly insist that peer use 192.244.177.2 as own side address and don't permit it to use any IP address but 192.244.177.2. When peer request another IP address, I always suggest that it use 192.244.177.2.
•   My interface netmask will be 255.255.255.0.
This is all fine when each side has a pre-determined IP address, however it is often the case that one side is acting as a server which controls all IP addresses and the other side should obey the direction from it. In order to allow more flexible behavior, `ifaddr' variable allows the user to specify IP address more loosely:
    set ifaddr 192.244.177.38/24 192.244.177.2/20
A number followed by a slash (/) represent the number of bits significant in the IP address. The above example signifies that:
•   I'd like to use 192.244.177.38 as my address if it is possible, but I'll also accept any IP address between 192.244.177.0 and 192.244.177.255.
•   I'd like to make him use 192.244.177.2 as his own address, but I'll also permit him to use any IP address between 192.244.176.0 and 192.244.191.255.
•   As you may have already noticed, 192.244.177.2 is equivalent to saying 192.244.177.2/32.
•   As an exception, 0 is equivalent to 0.0.0.0/0, meaning that I have no preferred IP address and will obey the remote peer's selection. When using zero, no routing table entries will be made until a connection is established.
•   192.244.177.2/0 means that I'll accept/permit any IP address but I'll try to insist that 192.244.177.2 be used first.

CONNECTING WITH YOUR INTERNET SERVICE PROVIDER
The following steps should be taken when connecting to your ISP:

1.  Describe your provider's phone number(s) in the dial script using the “set phone” command. This command allows you to set multiple phone numbers for dialing and redialing separated by a colon (:). For example:

        set phone "1234567:2345678"

    Here, the first number is attempted. If the connection fails, the second number is attempted after the next number redial period. If the second number also fails, the first is tried again after the redial period has expired. The selected phone number is substituted for the \T string in the “set dial” command (see below).

2.  Set up your redial requirements using “set redial”. For example, if you have a bad telephone line or your provider is usually engaged (not so common these days), you may want to specify the following:

        set redial 10 4

    This says that up to 4 phone calls should be attempted with a pause of 10 seconds before dialing the first number again.

3.  Describe your login procedure using the “set dial” and “set login” commands. The “set dial” command is used to talk to your modem and establish a link with your ISP, for example:

        set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 4 \"\" ATZ OK-ATZ-OK ATDT\\T TIMEOUT 60 CONNECT"

    This modem "chat" string means:

    •   Abort if the string "BUSY" or "NO CARRIER" are received.

    •   Set the timeout to 4.

    •   Expect nothing.

    •   Send ATZ.

    •   Expect OK. If that's not received, send ATZ and expect OK.

    •   Send ATDTxxxxxxx where xxxxxxx is the next number in the phone list from above.

    •   Set the timeout to 60.

    •   Wait for the CONNECT string.
    Once the connection is established, the login script is executed. This script is written in the same style as the dial script:

        set login "TIMEOUT 15 login:-\\r-login: awfulhak word: xxx ocol: PPP HELLO"

    This login "chat" string means:

    •   Set the timeout to 15 seconds.

    •   Expect "login:". If it's not received, send a carriage return and expect "login:" again.

    •   Send "awfulhak"

    •   Expect "word:" (the tail end of a "Password:" prompt).

    •   Send "xxx".

    •   Expect "ocol:" (the tail end of a "Protocol:" prompt).

    •   Send "PPP".

    •   Expect "HELLO".

    Login scripts vary greatly between ISPs.

4.  Use “set line” and “set sp” to specify your serial line and speed, for example:

        set line /dev/cuaa0
        set sp 115200

    Cuaa0 is the first serial port on FreeBSD. Cuaa1 is the second etc. A speed of 115200 should be specified if you have a modem capable of bit rates of 28800 or more. In general, the serial speed should be about four times the modem speed.

5.  Use “set ifaddr” command to define the IP address.

    •   If you know what IP address your provider uses, then use it as the remote address, otherwise choose something like 10.0.0.2/0 (see below).

    •   If your provider has assigned a particular IP address to you, then use it as your address.

    •   If your provider assigns your address dynamically, choose a suitably unobtrusive and unspecific IP number as your address. 10.0.0.1/0 would be appropriate. The bit after the / specifies how many bits of the address you consider to be important, so if you wanted to insist on something in the class C network 1.2.3.0, you could specify 1.2.3.1/24.

    An example for a connection where you don't know your IP number or your ISPs IP number would be:

        set ifaddr 10.10.10.10/0 10.10.11.11/0 255.255.255.0

6.  In most cases, your ISP will also be your default router. If this is the case, add the lines

        delete ALL
        add 0 0 10.10.11.11

    to ppp.conf.

    This tells ppp to delete all non-direct routing entries for the tun interface that ppp is running on, then to add a default route to 10.10.11.11.

    If you're using dynamic IP numbers, you must also put these two lines in the ppp.linkup file:

        delete ALL
        add 0 0 HISADDR

    HISADDR is a macro meaning the "other side"s IP number, and is available once an IP number has been agreed (using LCP). Now, once a connection is established, ppp will delete all non-direct interface routes, and add a default route pointing at the peers IP number. You should use the same label as the one used in ppp.conf.

    If commands are being typed interactively, the only requirement is to type

        add 0 0 HISADDR

    after a successful dial.

7.  If your provider requests that you use PAP/CHAP authentication methods, add the next lines to your ppp.conf file:

        enable pap (or enable chap)
        disable chap (or disable pap)
        set authname MyName
        set authkey MyPassword

Please refer to /etc/ppp/ppp.conf.sample and /etc/ppp/ppp.linkup.sample for some real examples. The pmdemand label should be appropriate for most ISPs.

LOGGING FACILITY
ppp is able to generate the following log info via syslog(3):
Async Dump async level packet in hex
Carrier Log Chat lines with 'CARRIER'
Chat Generate Chat script trace log
Command Log commands executed
Connect Generate complete Chat log
Debug Log (very verbose) debug information
HDLC Dump HDLC packet in hex
LCP Generate LCP/IPCP packet trace
Link Log address assignments and link up/down events
LQM Generate LQR report
Phase Phase transition log output
TCP/IP Dump all TCP/IP packets
TUN Include the tun device on each log line
Warning Output to the terminal device. If there is currently no
terminal, output is sent to the log file using LOG_WARNING.
Error Output to both the terminal device and the log file using
LOG_ERROR.
Alert Output to the log file using LOG_ALERT
The “set log” command allows you to set logging output level, of which multiple levels can be specified. The default is equivalent to “set log Carrier Link Phase”. If The first argument to “set log” begins with a '+' or a '-' character, the current log levels are not cleared, for example:

    PPP ON awfulhak> show log
    Log: Carrier Link Phase
    PPP ON awfulhak> set log -Link +tcp/ip
    PPP ON awfulhak> show log
    Log: Carrier Phase TCP/IP

Log messages of level Warning, Error and Alert are not controlable using “set log”.

SIGNAL HANDLING
Ppp deals with the following signals:

INT Receipt of this signal causes the termination of the current connection (if any). This will cause ppp to exit unless it is in -auto or -ddial mode.

HUP, TERM & QUIT
    These signals tell ppp to exit.

USR1
    This signal, when not in interactive mode, tells ppp to close any existing server socket and open an internet socket using the default rules for choosing a port number - that is, using port 3000 plus the current tunnel device number.

PPP COMMAND LIST
This section lists the available commands and their effect. They are usable either from an interactive ppp session, from a configuration file or from a telnet session.

accept|deny|enable|disable option....
    These directives tell ppp how to negotiate the initial connection with the peer. Each “option” has a default of either accept or deny and enable or disable. “Accept” means that the option will be ACK'd if the peer asks for it. “Deny” means that the option will be NAK'd if the peer asks for it. “Enable” means that the option will be requested by us. “Disable” means that the option will not be requested by us.

    “Option” may be one of the following:

    vjcomp
        Default: Enabled and Accepted. This option decides if Van Jacobson header compression will be used.

    lqr Default: Enabled and Accepted. This option decides if Link Quality Requests will be sent. LQR is a protocol that allows ppp to determine that the link is down without relying on the modems carrier detect.

    chap
        Default: Disabled and Accepted. CHAP stands for Challenge Handshake Authentication Protocol. Only one of CHAP and PAP (below) may be negotiated. With CHAP, the authenticator sends a "challenge" message to its peer. The peer uses a one-way hash function to encrypt the challenge and sends the result back. The authenticator does the same, and compares the results. The advantage of this mechanism is that no passwords are sent across the connection. A challenge is made when the connection is first made. Subsequent challenges may occur. When using CHAP, an “AuthName” and an “AuthKey” must be specified either in ppp.conf or in ppp.secret.

    pap Default: Disabled and Accepted. PAP stands for Password Authentication Protocol. Only one of PAP and CHAP (above) may be negotiated. With PAP, the ID and Password are sent repeatedly to the peer until authentication is acknowledged or the connection is terminated. This is a rather poor security mechanism. It is only performed when the connection is first established. When using PAP, an “AuthName” and an “AuthKey” must be specified either in ppp.conf or in ppp.secret (although see the “passwdauth” option below).

    acfcomp
        Default: Enabled and Accepted. ACFComp stands for Address and Control Field Compression. Non LCP packets usually have very similar address and control fields - making them easily compressable.

    protocomp
        Default: Enabled and Accepted. This option is used to negotiate PFC (Protocol Field Compression), a mechanism where the protocol field number is reduced to one octet rather than two.

    pred1
        Default: Enabled and Accepted. This option decides if Predictor 1 compression will be used.

    proxy
        Default: Disabled and Denied. Unlike the other options (except passwdauth below), this is not negotiated with the peer. Therefore, accepting or denying it is of no use. Enabling this option will tell ppp to proxy ARP for the peer.

    msext
        Default: Disabled and Accepted. This option allows the use of Microsoft's ppp extensions, supporting the negotiation of the Microsoft PPP DNS and the Microsoft NetBIOS NS.

    passwdauth
        Default: Disabled and Denied. Unlike the other options (except “proxy” above), this is not negotiated with the peer. Therefore, accepting or denying it is of no use. Enabling this option will tell the PAP authentication code to use the passwd file to authenticate the caller rather than the ppp.secret file.

add dest mask gateway
    “Dest” is the destination IP address and “mask” is its mask. “0 0” refers to the default route. “Gateway” is the next hop gateway to get to the given “dest” machine/network.

close
    Close the current connection (but don't quit).

delete ALL | dest [gateway [mask]]
    If “ALL” is specified, all non-direct entries in the routing for the interface that ppp is using are deleted. This means all entries for tunX, except the entry representing the actual link. When “ALL” is not used, any existing route with the given “dest”, destination network “mask” and “gateway” is deleted. The default “mask” value is 0.0.0.0.

dial|call [remote]
    If “remote” is specified, a connection is established using the “dial” and “login” scripts for the given “remote” system. Otherwise, the current settings are used to establish the connection.

display
    Displays the current status of the negotiable protocol values as specified under “accept|deny|enable|disable option....” above.

passwd pass
    Specify the password required for access to the full ppp command set.

load [remote]
    Load the given “remote” label. If “remote” is not given, the “default” label is assumed.

save
    This option is not (yet) implemented.

set[up] var value
    This option allows the setting of any of the following variables:

    set accmap hex-value
        ACCMap stands for Asyncronous Control Character Map. This is always negotiated with the peer, and defaults to a value of 0x00000000. This protocol is required to defeat hardware that depends on passing certain characters from end to end (such as XON/XOFF etc).

    set filter-name rule-no action [src_addr/src_width]
        [dst_addr/dst_width] [proto [src [lt|eq|gt] port ]] [dst [lt|eq|gt] port] [estab]

        Ppp supports four filter sets. The afilter specifies packets that keep the connection alive - reseting the idle timer. The dfilter specifies packets that cause ppp to dial when in -auto mode. The ifilter specifies packets that are allowed to travel into the machine and the ofilter specifies packets that are allowed out of the machine. By default all filter sets allow all packets to pass. Rules are processed in order according to “n”. Up to 20 rules may be given for each set. If a packet doesn't match any of the rules in a given set, it is discarded. In the case of ifilters and ofilters, this means that the packet is dropped. In the case of afilters it means that the packet will not reset the idle timer and in the case of dfilters it means that the packet will not trigger a dial. Refer to the section on PACKET FILTERING above for further details.

    set authkey|key value
        This sets the authentication key (or password) used in PAP or CHAP negotiation to the given value. It can also be used to specify the password to be used in the dial or login scripts, preventing the actual password from being logged.

    set authname id
        This sets the authentication id used in PAP or CHAP negotiation.

    set ctsrts
        This sets hardware flow control and is the default.

    set device|line value
        This sets the device to which ppp will talk to the given “value”. All serial device names are expected to begin with /dev/. If “value” does not begin with /dev/, it must be of the format “host:port”. If this is the case, ppp will attempt to connect to the given “host” on the given “port”. Refer to the section on PPP OVER TCP above for further details.

    set dial chat-script
        This specifies the chat script that will be used to dial the other side. See also the set login command below. Refer to chat(8) and to the example configuration files for details of the chat script format. The string \\T will be replaced with the current phone number (see “set phone” below) and the string \\P will be replaced with the password (see “set key” above).

    set hangup chat-script
        This specifies the chat script that will be used to reset the modem before it is closed. It should not normally be necessary, but can be used for devices that fail to reset themselves properly on close.

    set escape value...
        This option is similar to the “set accmap” option above. It allows the user to specify a set of characters that will be `escaped' as they travel across the link.

    set ifaddr myaddr hisaddr mask
        This command specifies the IP addresses that will be used during LCP negotiation. Addresses are specified using the format
            a.b.c.d/n
        Where a.b.c.d is the preferred IP, but n specifies how many bits of the address we will insist on. If the /n bit is omitted, it defaults to /32 unless the IP address is 0.0.0.0 in which case the mask defaults to /0.

    set log [+|-]value...
        This command allows the adjustment of the current log level. Please refer to the Logging Facility section for further details.

    set login chat-script
        This chat-script compliments the dial-script. If both are specified, the login script will be executed after the dial script. Escape sequences available in the dial script are also available here.

    set mru value
        The default MRU is 1500. If it is increased, the other side *may* increase its mtu. There is no use decreasing the MRU to below the default as the PPP protocol *must* be able to accept packets of at least 1500 octets.

    set mtu value
        The default MTU is 1500. This may be increased by the MRU specified by the peer. It may only be subsequently decreased by this option. Increasing it is not valid as the peer is not necessarily able to receive the increased packet size.

    set openmode active|passive
        By default, openmode is always active. That is, ppp will always initiate LCP negotiation. If you want to wait for the peer to initiate LCP negotiation, you may use the value “passive”.

    set parity odd|even|none|mark
        This allows the line parity to be set. The default value is none.

    set phone telno[:telno]...
        This allows the specification of the phone number to be used in place of the \\T string in the dial and login chat scripts. Multiple phone numbers may be given seperated by a colon (:). If multiple numbers are given, ppp will dial them in rotation until a connection is made, retrying the maximum number of times specified by “set redial” below. In -background mode, each number is attempted at most once.

    set reconnect timeout ntries
        Should the line drop unexpectedly (due to loss of CD or LQR failure), a connection will be re-established after the given “timeout”. The line will be re-connected at most “ntries” times. “Ntries” defaults to zero. A value of “random” for “timeout” will result in a variable pause, somewhere between 0 and 30 seconds.

    set redial seconds[.nseconds] [attempts]
        Ppp can be instructed to attempt to redial “attempts” times. If more than one number is specified (see “set phone” above), a pause of “nseconds” is taken before dialing each number. A pause of “seconds” is taken before starting at the first number again. A value of “random” may be used here too.

    set server|socket TcpPort|LocalName|none [mask]
        Normally, when not in interactive mode, ppp listens to a tcp socket for incoming command connections. The socket number is calculated as 3000 plus the number of the tunnel device that ppp opened. So, for example, if ppp opened tun2, socket 3002 would be used.

        Using this command, you can specify your own port number, a local domain socket (specified as an absolute file name), or you can tell ppp not to accept any command connections. If a local domain socket is specified, you may also specify an octal mask that should be set before creating the socket. See also the use of the USR1 signal.

    set speed value
        This sets the speed of the serial device.

    set timeout Idle [lqr [retry]]
        This command allows the setting of the idle timer, the LQR timer (if enabled) and the retry timer.

    set ns x.x.x.x
        This option allows the setting of the Microsoft PPP DNS server that will be negotiated.

    set nbns
        This option allows the setting of the Microsoft NetBIOS DNS server that will be negotiated.

    set help|?
        This command gives a summary of available set commands.

shell|! [command]
    Execute a shell according to the value of the SHELL environment variable. If “command” is specified, it is executed without a parent shell. Note, it's possible to use the HISADDR, INTERFACE and MYADDR symbols here. Also note that if you use the ! character, you must have a space between it and “command”.

show var
    This command allows the user to examine the following:

    show [adio]filter
        List the current rules for the given filter.

    show auth
        Show the current authname and authkey.

    show ccp
        Show the current CCP statistics.

    show compress
        Show the current compress statistics.

    show escape
        Show the current escape characters.

    show hdlc
        Show the current HDLC statistics.

    show ipcp
        Show the current IPCP statistics.

    show lcp
        Show the current LCP statistics.

    show log
        Show the current log values.

    show mem
        Show current memory statistics.

    show modem
        Show current modem statistics.

    show mru
        Show the current MRU.

    show mtu
        Show the current MTU.

    show proto
        Show current protocol totals.

    show reconnect
        Show the current reconnect values.

    show redial
        Show the current redial values.

    show route
        Show the current routing tables.

    show timeout
        Show the current timeout values.

    show msext
        Show the current Microsoft extension values.

    show version
        Show the current version number of ppp.

    show help|?
        Give a summary of available show commands.

term
    Go into terminal mode. Characters typed at the keyboard are sent to the modem. Characters read from the modem are displayed on the screen. When a ppp peer is detected on the other side of the modem, ppp automatically enables Packet Mode and goes back into command mode.

alias .....
    This command allows the control of the aliasing (or masquerading) facilities that are built into ppp. Until this code is required, it is not loaded by ppp, and it is quite possible that the alias library is not installed on your system (some administrators consider it a security risk). If aliasing is enabled on your system, the following commands are possible:

    alias enable [yes|no]
        This command either switches aliasing on or turns it off. The -alias command line flag is synonomous with “alias enable yes”.

    alias port [proto targetIP:targetPORT [aliasIP:]aliasPORT]
        This command allows us to redirect connections arriving at “aliasPORT” for machine [aliasIP] to “targetPORT” on “targetIP”. If proto is specified, only connections of the given protocol are matched. This option is useful if you wish to things like internet phone on the machines behind your gateway.

    alias addr [addr_local addr_alias]
        This command allows data for “addr_alias” to be redirected to “addr_local”. It is useful if you own a small number of real IP numbers that you wish to map to specific machines behind your gateway.

    alias deny_incoming [yes|no]
        If set to yes, this command will refuse all incoming connections by dropping the packets in much the same way as a firewall would.

    alias log [yes|no]
        This option causes various aliasing statistics and information to be logged to the file /var/log/alias.log.

    alias same_ports [yes|no]
        When enabled, this command will tell the alias library attempt to avoid changing the port number on outgoing packets. This is useful if you want to support protocols such as RPC and LPD which require connections to come from a well known port.

    alias use_sockets [yes|no]
        When enabled, this option tells the alias library to create a socket so that it can guarantee a correct incoming ftp data or IRC connection.

    alias unregistered_only [yes|no]
        Only alter outgoing packets with an unregistered source ad- dress. According to rfc 1918, unregistered source addresses are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.

    alias help|?
        This command gives a summary of available alias commands.

quit|bye [all]
    Exit ppp. If ppp is in interactive mode or if the “all” argument is given, ppp will exit, closing the connection. A simple “quit” issued from a telnet session will not close the current connection.

help|? [command]
    Show a list of available commands. If “command” is specified, show the usage string for that command.

down
    Bring the link down ungracefully. It's not considered polite to use this command.

MORE DETAILS
•   Read the example configuration files. They are a good source of information.
•   Use “help”, “show”?, “alias”?, “set”? and “set? <var>” commands.

FILES
Ppp refers to four files: ppp.conf, ppp.linkup, ppp.linkdown and ppp.secret. These files are placed in /etc/ppp, but the user can create his own files under his $HOME directory as .ppp.conf, .ppp.linkup, .ppp.linkdown and .ppp.secret. ppp will always try to consult the user's personal setup first.
$HOME/ppp/.ppp.[conf|linkup|linkdown|secret] User dependent configuration files. /etc/ppp/ppp.conf System default configuration file. /etc/ppp/ppp.secret An authorization file for each system. /etc/ppp/ppp.linkup A file to check when ppp establishes a network level connection. /etc/ppp/ppp.linkdown A file to check when ppp closes a network level connection. /var/log/ppp.tun0.log Logging and debugging information file. /var/spool/lock/LCK..* tty port locking file. Refer to uucplock(8) for further details. /var/run/tunX.pid The process id (pid) of the ppp program connected to the tunX device, where -background, -auto and -ddial modes. /var/run/ttyXX.pid The tun interface used by this port. Again, this file is only created in -background, -auto and -ddial modes. /etc/services Get port number if port number is using service name.

SEE ALSO
chat(8), pppd(8), uucplock(3), syslog(3), syslog.conf(5), syslogd(8)

HISTORY
This program was originally written by Toshiharu OHNO (tony-o@iij.ad.jp), and was submitted to FreeBSD-2.0.5 by Atsushi Murai (amurai@spec.co.jp). It's since had an enormous face lift and looks substantially different.