PPP and Asynchronous Interfaces

Document revision:	1.3 (October 31, 2007, 13:15 GMT)
Applies to:	V3.0

General Information

Summary

PPP (Point-to-Point Protocol) provides a method for transmitting datagrams over serial point-to-point links. Physically it relies on COM1 and COM2 ports from standard PC hardware configurations. These appear as serial0 and serial1 automatically. You can add more serial ports to use the router for a modem pool using these adapters:

Specifications

Packages required: ppp
License required: Level1
Submenu level: /interface ppp-client, /interface ppp-server
Standards and Technologies: PPP (RFC 1661)
Hardware usage: Not significant

Additional Resources

Serial Port Configuration

Submenu level: /port

Property Description

baud-rate (integer; default: 9600) - data rate of the port

data-bits (7 | 8; default: 8) - number of bits per character transmitted

flow-control (none | hardware | xon-xoff; default: hardware) - flow control method

name (name; default: serialN) - port name

parity (none | even | odd; default: none) - character parity check method

stop-bits (1 | 2; default: 1) - number of stop bits after each character transmitted

used-by (read-only: text) - shows the user (if any) of the port. Only unused ports can be used in PPP setup

Notes

Keep in mind that baud-rate, data-bits, parity, stop-bits and flow control parameters must be the same for both communicating parties.

Example

[admin@MikroTik] > /port print
  # NAME                             USED-BY                          BAUD-RATE
  0 serial0                          Serial Console                   9600
  1 databooster1                                                      9600
  2 databooster2                                                      9600
  3 databooster3                                                      9600
  4 databooster4                                                      9600
  5 databooster5                                                      9600
  6 databooster6                                                      9600
  7 databooster7                                                      9600
  8 databooster8                                                      9600
  9 cycladesA1                                                        9600
 10 cycladesA2                                                        9600
 11 cycladesA3                                                        9600
 12 cycladesA4                                                        9600
 13 cycladesA5                                                        9600
 14 cycladesA6                                                        9600
 15 cycladesA7                                                        9600
 16 cycladesA8                                                        9600
[admin@MikroTik] > set 9 baud-rate=38400
[admin@MikroTik] >

PPP Server Setup

Submenu level: /interface ppp-server

Description

PPP server provides a remode connection service for users. When dialing in, the users can be authenticated locally using the local user database in the /user menu, or at the RADIUS server specified in the /ip ppp settings.

Property Description

authentication (multiple choice: mschap2, mschap1, chap, pap; default: mschap2, mschap1, chap, pap) - authentication protocol(s)

max-mru (integer; default: 1500) - maximum value of MRU (Maximum Receive Unit) allowed on this link. Largest packet that can be received

max-mtu (integer; default: 1500) - maximum value of MTU (Maximum Transmission Unit) allowed on this link. Maximum packet size to be transmitted

modem-init (text; default: "") - modem initialization string. For example, you may use "s11=40" to improve dialing speed

mrru (integer) - maximum packet size that can be received on the link. If packet is bigger than tunnel MTU, it will be split into multiple packets. That way it is possible to send full size (1500 or even 1514) packets over PPTP or L2TP tunnels.

name (name; default: ppp-inN) - interface name for reference

null-modem (no | yes; default: no) - enable/disable null-modem mode (when enabled, no modem initialization strings are sent)

port (name) - serial port name

profile (name; default: default) - default (fall-back) profile name used for the link

ring-count (integer; default: 1) - number of rings to wait before answering phone

Notes

Specifying MRRU means enabling MP (Multilink PPP) over single link. This protocol is used to split big packets into smaller ones. Under Windows it can be enabled in Networking tag, Settings button, "Negotiate multi-link for single link connections". Their MRRU is hardcoded to 1614. This setting is usefull to overcome PathMTU discovery failures. The MP should be enabled on both peers.

Example

You can add a PPP server using the add command:

[admin@MikroTik] interface ppp-server> add name=test port=serial1
[admin@MikroTik] interface ppp-server> print
Flags: X - disabled, R - running
  0 X  name="test" max-mtu=1500 max-mru=1500 mrru=disabled port=serial1
       authentication=pap,chap,mschap1,mschap2 profile=default modem-init=""
       ring-count=1 null-modem=no
[admin@MikroTik] interface ppp-server> enable 0
[admin@MikroTik] interface ppp-server> monitor test
            status: "waiting for call..."

[admin@MikroTik] interface ppp-server>

PPP Client Setup

Submenu level: /interface ppp-client

Description

The section describes PPP clients configuration routines.

Property Description

add-default-route (yes | no; default: no) - add PPP remote address as a default route

allow (multiple choice: mschap2, mschap1, chap, pap; default: mschap2, mschap1, chap, pap) - the protocol to allow the client to use for authentication

dial-command (text; default: "ATDT") - AT dial command to use. The default one sets tone diling mode

dial-on-demand (yes | no; default: no) - enable/disable dial on demand

max-mru (integer; default: 1500) - maximum value of MRU (Maximum Receive Unit) allowed on this link. Largest packet that can be received

max-mtu (integer; default: 1500) - maximum value of MTU (Maximum Transmission Unit) allowed on this link. Maximum packet size to be transmitted

modem-init (text; default: "") - modem initialization strings. You may use "s11=40" to improve dialing speed

mrru (integer) - maximum packet size that can be received on the link. If packet is bigger than tunnel MTU, it will be split into multiple packets. That way it is possible to send full size (1500 or even 1514) packets over PPTP or L2TP tunnels.

name (name; default: ppp-inN) - interface name for reference

null-modem (no | yes; default: no) - enable/disable null-modem mode (when enabled, no modem initialization strings are sent)

password (text; default: "") - P2P user password on the remote server to use for dialout

phone (integer; default: "") - phone number for dialout

port (name) - serial port

profile (name; default: default) - local profile to use for dialout

use-peer-dns (yes | no; default: no) - use DNS server settings from the remote server

user (text; default: "") - P2P user name on the remote server to use for dialout

Notes

Additional client profiles must be configured on the server side for clients to accomplish logon procedure. For more information see Related Documents section.

PPP client profiles must match at least partially (local-address and values related to encryption should match) with corresponding remote server values.

Example

You can add a PPP client using the add command:

[admin@MikroTik] interface ppp-client> add name=test user=test port=serial1 \
\... add-default-route=yes
[admin@MikroTik] interface ppp-client> print
Flags: X - disabled, R - running
  0 X  name="test" mtu=1500 mru=1500 port=serial1 user="test" password=""
       profile=default phone="" tone-dial=yes modem-init="" null-modem=no
       dial-on-demand=no add-default-route=yes use-peer-dns=no

[admin@MikroTik] interface ppp-client> enable 0
[admin@MikroTik] interface ppp-client> monitor test
[admin@MikroTik] interface ppp-client> monitor 0
           status: "dialing out..."

[admin@MikroTik] interface ppp-client>

PPP Application Example

Client - Server Setup

In this example we will consider the following network setup:

For a typical server setup we need to add one user to the R1 and configure the PPP server.

[admin@MikroTik] ppp secret> add name=test password=test local-address=3.3.3.1 \
\... remote-address=3.3.3.2
[admin@MikroTik] ppp secret> print
Flags: X - disabled
  0   name="test" service=any caller-id="" password="test" profile=default
      local-address=3.3.3.1 remote-address=3.3.3.2 routes=""

[admin@MikroTik] ppp secret> /int ppp-server
[admin@MikroTik] interface ppp-server> add port=serial1 disabled=no
[admin@MikroTik] interface ppp-server> print
Flags: X - disabled, R - running
  0    name="ppp-in1" mtu=1500 mru=1500 port=serial1
       authentication=mschap2,mschap1,chap,pap profile=default modem-init=""
       ring-count=1 null-modem=no

[admin@MikroTik] interface ppp-server>

Now we need to setup the client to connect to the server:

[admin@MikroTik] interface ppp-client> add port=serial1 user=test password=test \
\... phone=132
[admin@MikroTik] interface ppp-client> print
Flags: X - disabled, R - running
  0 X  name="ppp-out1" mtu=1500 mru=1500 port=serial1 user="test"
       password="test" profile=default phone="132" tone-dial=yes
       modem-init="" null-modem=no dial-on-demand=no add-default-route=no
       use-peer-dns=no

[admin@MikroTik] interface ppp-client> enable 0

After a short duration of time the routers will be able to ping each other: 
[admin@MikroTik] interface ppp-client> /ping 3.3.3.1
3.3.3.1 64 byte ping: ttl=64 time=43 ms
3.3.3.1 64 byte ping: ttl=64 time=11 ms
3.3.3.1 64 byte ping: ttl=64 time=12 ms
3.3.3.1 64 byte ping: ttl=64 time=11 ms
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 11/19.2/43 ms
[admin@MikroTik] interface ppp-client>