Manual:Interface/PPTP
Applies to RouterOS: v3, v4
Summary
Standards: RFC 2637
PPTP is a secure tunnel for transporting IP traffic using PPP. PPTP encapsulates PPP in virtual lines that run over IP. PPTP incorporates PPP and MPPE (Microsoft Point to Point Encryption) to make encrypted links. The purpose of this protocol is to make well-managed secure connections between routers as well as between routers and PPTP clients (clients are available for and/or included in almost all OSs including Windows).
Multilink PPP (MP) is supported in order to provide MRRU (the ability to transmit full-sized 1500 and larger packets) and bridging over PPP links (using Bridge Control Protocol (BCP) that allows to send raw Ethernet frames over PPP links). This way it is possible to setup bridging without EoIP. The bridge should either have an administratively set MAC address or an Ethernet-like interface in it, as PPP links do not have MAC addresses.
PPTP includes PPP authentication and accounting for each PPTP connection. Full authentication and accounting of each connection may be done through a RADIUS client or locally.
MPPE 40bit RC4 and MPPE 128bit RC4 encryption are supported.
PPTP traffic uses TCP port 1723 and IP protocol GRE (Generic Routing Encapsulation, IP protocol ID 47), as assigned by the Internet Assigned Numbers Authority (IANA). PPTP can be used with most firewalls and routers by enabling traffic destined for TCP port 1723 and protocol 47 traffic to be routed through the firewall or router.
PPTP connections may be limited or impossible to setup though a masqueraded/NAT IP connection. Please see the Microsoft and RFC links listed below for more information.
PPTP Client
Sub-menu: /interface pptp-client
Properties
| Property | Description |
|---|---|
| add-default-route (yes | no; Default: no) | Whether to add PPTP remote address as a default route. |
| allow (mschap2 | mschap1 | chap | pap; Default: mschap2, mschap1, chap, pap) | Allowed authentication methods. |
| connect-to (IP; Default: ) | Remote address of PPTP server |
| dial-on-demand (yes | no; Default: no) | |
| disabled (yes | no; Default: yes) | Whether interface is disabled or not. By default it is disabled |
| max-mru (integer; Default: 1460) | Maximum Receive Unit. Max packet size that PPTP interface will be able to receive without packet fragmentation. |
| max-mtu (integer; Default: 1460) | Maximum Transmission Unit. Max packet size that PPTP interface will be able to send without packet fragmentation. |
| mrru (disabled | integer; Default: disabled) | Maximum packet size that can be received on the link. If a packet is bigger than tunnel MTU, it will be split into multiple packets, allowing full size IP or Ethernet packets to be sent over the tunnel. Read more >> |
| name (string; Default: ) | Descriptive name of the interface. |
| password (string; Default: "") | Password used for authentication. |
| profile (name; Default: default-encryption) | Used PPP profile. |
| user (string; Default: ) | User name used for authentication. |
Quick example
This example demonstrates how to set up PPTP client with username "pptp-hm", password "123" and server 10.1.101.100
[admin@dzeltenais_burkaans] /interface pptp-client>add name=pptp-hm user=pptp-hm password=123 \
\... connect-to=10.1.101.100 disabled=no
[admin@dzeltenais_burkaans] /interface pptp-client> print detail
Flags: X - disabled, R - running
0 name="pptp-hm" max-mtu=1460 max-mru=1460 mrru=disabled
connect-to=10.1.101.100 user="pptp-hm" password="123"
profile=default-encryption add-default-route=no dial-on-demand=no
allow=pap,chap,mschap1,mschap2
PPTP Server
Sub-menu: /interface pptp-server
This sub-menu shows interfaces for each connected PPTP clients.
An interface is created for each tunnel established to the given server. There are two types of interfaces in PPTP server's configuration
- Static interfaces are added administratively if there is a need to reference the particular interface name (in firewall rules or elsewhere) created for the particular user.
- Dynamic interfaces are added to this list automatically whenever a user is connected and its username does not match any existing static entry (or in case the entry is active already, as there can not be two separate tunnel interfaces referenced by the same name).
Dynamic interfaces appear when a user connects and disappear once the user disconnects, so it is impossible to reference the tunnel created for that use in router configuration (for example, in firewall), so if you need a persistent rules for that user, create a static entry for him/her. Otherwise it is safe to use dynamic configuration.
Note: in both cases PPP users must be configured properly - static entries do not replace PPP configuration.
Server configuration
Sub-menu: /interface pptp-server server
Properties:
| Property | Description |
|---|---|
| authentication (pap | chap | mschap1 | mschap2; Default: mschap1,mschap2) | Authentication methods that server will accept. |
| default-profile (name; Default: default-encryption) | |
| enabled (yes | no; Default: no) | Defines whether PPTP server is enabled or not. |
| keepalive-timeout (time; Default: 30) | Defines the time period (in seconds) after which the router is starting to send keepalive packets every second. If no traffic and no keepalive responses has came for that period of time (i.e. 2 * keepalive-timeout), not responding client is proclaimed disconnected |
| max-mru (integer; Default: 1460) | Maximum Receive Unit. Max packet size that PPTP interface will be able to receive without packet fragmentation. |
| max-mtu (integer; Default: 1460) | Maximum Transmission Unit. Max packet size that PPTP interface will be able to send without packet fragmentation. |
| mrru (disabled | integer; Default: disabled) | Maximum packet size that can be received on the link. If a packet is bigger than tunnel MTU, it will be split into multiple packets, allowing full size IP or Ethernet packets to be sent over the tunnel. Read more >> |
To enable PPTP server:
[admin@MikroTik] interface pptp-server server> set enabled=yes
[admin@MikroTik] interface pptp-server server> print
enabled: yes
max-mtu: 1460
max-mru: 1460
mrru: disabled
authentication: mschap2,mschap1
keepalive-timeout: 30
default-profile: default
[admin@MikroTik] interface pptp-server server>
Monitoring
Monitor command can be used to monitor status of the tunnel on both client and server.
[admin@dzeltenais_burkaans] /interface pptp-client> monitor 0
status: "connected"
uptime: 7h24m18s
idle-time: 6h21m4s
encoding: "MPPE128 stateless"
mtu: 1460
mru: 1460
Read-only properties
| Property | Description |
|---|---|
| status () | Current PPTP status. Value other than "connected" indicates that there are some problems estabising tunnel. |
| uptime (time) | Elapsed time since tunnel was established. |
| idle-time (time) | Elapsed time since last activity on the tunnel. |
| encoding () | Used encryption method |
| mtu (integer) | Negotiated and used MTU |
| mru (integer) | Negotiated and used MRU |
Application Examples
Router-to-Router PPTP
The following is an example of connecting two Intranets using PPTP tunnel over the Internet.
Connecting Remote Client
The following example shows how to connect a computer to a remote office network over PPTP encrypted tunnel giving that computer an IP address from the same network as the remote office has (without need of bridging over EoIP tunnels)
Please, consult the respective manual on how to set up a PPTP client with the software You are using.