PPTP (Point to Point Tunnel Protocol) supports encrypted tunnels over IP. The MikroTik RouterOS implementation includes support fot PPTP client and server.
General applications of PPTP tunnels:
* For secure router-to-router tunnels over the Internet
* To link (bridge) local Intranets or LANs (when EoIP is also used)
* For mobile or remote clients to remotely access an Intranet/LAN of a company (see PPTP setup for Windows for more information)
Each PPTP connection is composed of a server and a client. The MikroTik RouterOS may function as a server or client – or, for various configurations, it may be the server for some connections and client for other connections. For example, the client created below could connect to a Windows 2000 server, another MikroTik Router, or another router which supports a PPTP server.
Description
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).
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 at the end of this section for more information.
PPTP Client Setup
Submenu level : /interface pptp-client
Property Description
name (name; default: pptp-out1) – interface name for reference
mtu (integer; default: 1460) – Maximum Transmit Unit. The optimal value is the MTU of the interface the tunnel is working over decreased by 40 (so, for 1500-byte ethernet link, set the MTU to 1460 to avoid fragmentation of packets)
mru (integer; default: 1460) – Maximum Receive Unit. The optimal value is the MTU of the interface the tunnel is working over decreased by 40 (so, for 1500-byte ethernet link, set the MRU to 1460 to avoid fragmentation of packets)
connect-to (IP address)- the IP address of the PPTP server to connect to
user (string)- user name to use when logging on to the remote server
password (string; default: “”)- user password to use when logging to the remote server
profile (name; default: default) – profile to use when connecting to the remote server
add-default-route (yes | no; default: no) – whether to use the server which this client is connected to as its default router (gateway)
Example
To set up PPTP client named test2 using username john with password john to connect to the 10.1.1.12 PPTP server and use it as the default gateway:
[admin@MikroTik] interface pptp-client> add name=test2 connect-to=10.1.1.12 \
\… user=john add-default-route=yes password=john
[admin@MikroTik] interface pptp-client> print
Flags: X – disabled, R – running
0 X name=”test2″ mtu=1460 mru=1460 connect-to=10.1.1.12 user=”john”
password=”john” profile=default add-default-route=yes
[admin@MikroTik] interface pptp-client> enable 0
Monitoring PPTP Client
Command name : /interface pptp-client monitor
Property Description
Statistics:
uptime (time) – connection time displayed in days, hours, minutes, and seconds
encoding (string) – encryption and encoding (if asymmetric, separated with ‘/’) being used in this connection
status (string) – status of the client:
# Dialing – attempting to make a connection
# Verifying password… – connection has been established to the server, password verification in progress
# Connected – self-explanatory
# Terminated – interface is not enabled or the other side will not establish a connection
Example
Example of an established connection:
[admin@MikroTik] interface pptp-client> monitor test2
uptime: 4h35s
encoding: MPPE 128 bit, stateless
status: Connected
[admin@MikroTik] interface pptp-client>
PPTP Server Setup
Submenu level : /interface pptp-server server
[admin@MikroTik] interface pptp-server server> print
enabled: no
mtu: 1460
mru: 1460
authentication: mschap2
default-profile: default
[admin@MikroTik] interface pptp-server server>
Description
The PPTP server supports unlimited connections from clients. For each current connection, a dynamic interface is created.
Property Description
enabled (yes | no; default: no) – defines whether PPTP server is enabled or not
mtu (integer; default: 1460) – Maximum Transmit Unit. The optimal value is the MTU of the interface the tunnel is working over decreased by 40 (so, for 1500-byte ethernet link, set the MTU to 1460 to avoid fragmentation of packets)
mru (integer; default: 1460) – Maximum Receive Unit. The optimal value is the MTU of the interface the tunnel is working over decreased by 40 (so, for 1500-byte ethernet link, set the MTU to 1460 to avoid fragmentation of packets)
authentication (multiple choice: pap | chap | mschap1 | mschap2; default: mschap2) – authentication algorithm
default-profile (name; default: default) – default profile to use
Example
To enable PPTP server:
[admin@MikroTik] interface pptp-server server> set enabled=yes
[admin@MikroTik] interface pptp-server server> print
enabled: yes
mtu: 1460
mru: 1460
authentication: mschap2
default-profile: default
[admin@MikroTik] interface pptp-server server>
PPTP Server Users
Submenu level : /interface pptp-server
Description
There are two types of items in PPTP server configuration – static users and dynamic connections. A dynamic connection can be established if the user database or the default-profile has its local-address and remote-address set correctly. When static users are added, the default profile may be left with its default values and only P2P user (in /ppp secret) should be configured. Note that in both cases P2P users must be configured properly.
Property Description
name – interface name
user – the name of the user that is configured statically or added dynamically
Statistics:
mtu – shows (cannot be set here) client’s MTU
client-address – shows (cannot be set here) the IP of the connected client
uptime – shows how long the client is connected
encoding (string) – encryption and encoding (if asymmetric, separated with ‘/’) being used in this connection
Example
To add a static entry for ex1 user:
[admin@MikroTik] interface pptp-server> add user=ex1
[admin@MikroTik] interface pptp-server> print
Flags: X – disabled, D – dynamic, R – running
# NAME USER MTU CLIENT-ADDRESS UPTIME ENC…
0 DR ex 1460 10.0.0.202 6m32s none
1 pptp-in1 ex1
[admin@MikroTik] interface pptp-server>
In this example an already connected user ex is shown besides the one we just added.
PPTP Router-to-Router Secure Tunnel Example
The following is an example of connecting two Intranets using an encrypted PPTP tunnel over the Internet.
There are two routers in this example:
* [HomeOffice]
Interface LocalHomeOffice 10.150.2.254/24
Interface ToInternet 192.168.80.1/24
* [RemoteOffice]
Interface ToInternet 192.168.81.1/24
Interface LocalRemoteOffice 10.150.1.254/24
Each router is connected to a different ISP. One router can access another router through the Internet.
On the PPTP server a user must be set up for the client:
[admin@HomeOffice] ppp secret> add name=ex service=pptp password=lkjrht
local-address=10.0.103.1 remote-address=10.0.103.2
[admin@HomeOffice] ppp secret> print detail
Flags: X – disabled
0 name=”ex” service=pptp caller-id=”" password=”lkjrht” profile=default
local-address=10.0.103.1 remote-address=10.0.103.2 routes==”"
[admin@HomeOffice] ppp secret>
Then the user should be added in the PPTP server list:
[admin@HomeOffice] interface pptp-server> add user=ex
[admin@HomeOffice] interface pptp-server> print
Flags: X – disabled, D – dynamic, R – running
# NAME USER MTU CLIENT-ADDRESS UPTIME ENC…
0 pptp-in1 ex
[admin@HomeOffice] interface pptp-server>
And finally, the server must be enabled:
[admin@HomeOffice] interface pptp-server server> set enabled=yes
[admin@HomeOffice] interface pptp-server server> print
enabled: yes
mtu: 1460
mru: 1460
authentication: mschap2
default-profile: default
[admin@HomeOffice] interface pptp-server server>
Add a PPTP client to the RemoteOffice router:
[admin@RemoteOffice] interface pptp-client> add connect-to=192.168.80.1 user=ex \
\… password=lkjrht disabled=no
[admin@RemoteOffice] interface pptp-client> print
Flags: X – disabled, R – running
0 R name=”pptp-out1″ mtu=1460 mru=1460 connect-to=192.168.80.1 user=”ex”
password=”lkjrht” profile=default add-default-route=no
[admin@RemoteOffice] interface pptp-client>
Thus, a PPTP tunnel is created between the routers. This tunnel is like an Ethernet point-to-point connection between the routers with IP addresses 10.0.103.1 and 10.0.103.2 at each router. It enables ‘direct’ communication between the routers over third party networks.
To route the local Intranets over the PPTP tunnel – add these routes:
[admin@HomeOffice] > ip route add dst-address 10.150.1.0/24 gateway 10.0.103.2
[admin@RemoteOffice] > ip route add dst-address 10.150.2.0/24 gateway 10.0.103.1
On the PPTP server it can alternatively be done using routes parameter of the user configuration:
[admin@HomeOffice] ppp secret> print detail
Flags: X – disabled
0 name=”ex” service=pptp caller-id=”" password=”lkjrht” profile=default
local-address=10.0.103.1 remote-address=10.0.103.2 routes==”"
[admin@HomeOffice] ppp secret> set 0 routes=”10.150.1.0/24 10.0.103.2 1″
[admin@HomeOffice] ppp secret> print detail
Flags: X – disabled
0 name=”ex” service=pptp caller-id=”" password=”lkjrht” profile=default
local-address=10.0.103.1 remote-address=10.0.103.2
routes=”10.150.1.0/24 10.0.103.2 1″
[admin@HomeOffice] ppp secret>
Test the PPTP tunnel connection:
[admin@RemoteOffice]> /ping 10.0.103.1
10.0.103.1 pong: ttl=255 time=3 ms
10.0.103.1 pong: ttl=255 time=3 ms
10.0.103.1 pong: ttl=255 time=3 ms
ping interrupted
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 3/3.0/3 ms
Test the connection through the PPTP tunnel to the LocalHomeOffice interface:
[admin@RemoteOffice]> /ping 10.150.2.254
10.150.2.254 pong: ttl=255 time=3 ms
10.150.2.254 pong: ttl=255 time=3 ms
10.150.2.254 pong: ttl=255 time=3 ms
ping interrupted
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 3/3.0/3 ms
To bridge a LAN over this secure tunnel, please see the example in the ‘EoIP’ section of the manual. To set the maximum speed for traffic over this tunnel, please consult the ‘Queues’ section.
Connecting a Remote Client via PPTP Tunnel
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.
The router in this example:
* [RemoteOffice]
Interface ToInternet 192.168.81.1/24
Interface Office 10.150.1.254/24
The client computer can access the router through the Internet.
On the PPTP server a user must be set up for the client:
[admin@RemoteOffice] ppp secret> add name=ex service=pptp password=lkjrht
local-address=10.150.1.254 remote-address=10.150.1.2
[admin@RemoteOffice] ppp secret> print detail
Flags: X – disabled
0 name=”ex” service=pptp caller-id=”" password=”lkjrht” profile=default
local-address=10.150.1.254 remote-address=10.150.1.2 routes==”"
[admin@RemoteOffice] ppp secret>
Then the user should be added in the PPTP server list:
[admin@RemoteOffice] interface pptp-server> add name=FromLaptop user=ex
[admin@RemoteOffice] interface pptp-server> print
Flags: X – disabled, D – dynamic, R – running
# NAME USER MTU CLIENT-ADDRESS UPTIME ENC…
0 FromLaptop ex
[admin@RemoteOffice] interface pptp-server>
And the server must be enabled:
[admin@RemoteOffice] interface pptp-server server> set enabled=yes
[admin@RemoteOffice] interface pptp-server server> print
enabled: yes
mtu: 1460
mru: 1460
authentication: mschap2
default-profile: default
[admin@RemoteOffice] interface pptp-server server>
Finally, the proxy APR must be enabled on the ‘Office’ interface:
[admin@RemoteOffice] interface ethernet> set Office arp=proxy-arp
[admin@RemoteOffice] interface ethernet> print
Flags: X – disabled, R – running
# NAME MTU MAC-ADDRESS ARP
0 R ToInternet 1500 00:30:4F:0B:7B:C1 enabled
1 R Office 1500 00:30:4F:06:62:12 proxy-arp
[admin@RemoteOffice] interface ethernet>
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