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Cannot determine ethernet address for proxy ARP (PPTP VPN)

I've installed pptpd on ubuntu 18.04 and I can connect to vpn with android and windows client but I have no internet access while the server has full internet access. In pptpd log I noticed the error "Cannot determine ethernet address for proxy ARP".

I've changed the dns in /etc/ppp/options.pptpd as below:

ms-dns 8.8.8.8
ms-dns 8.8.4.4

I've also created users in /etc/ppp/chap-secrets and clients can connect without problem (but with no internet access.)

I've also enabled IP forwarding in /etc/sysctl.conf

net.ipv4.ip_forward = 1

and execute this command:

sudo sysctl -p

I changed local and remote IPs in /etc/pptpd.conf as below:

localip 10.0.0.1
remoteip 10.0.0.100-200

And I also tried:

localip 192.168.0.1
remoteip 192.168.0.100-200

I configured firewall for IP masquerading:

sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

This is the ifconfig result:

photon@ubuntu1804:~$ ifconfig
ens160: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
    inet 162.223.91.163  netmask 255.255.255.192  broadcast 162.223.91.191
    inet6 fe80::250:56ff:fe94:32d0  prefixlen 64  scopeid 0x20<link>
    ether 00:50:56:94:32:d0  txqueuelen 1000  (Ethernet)
    RX packets 543184  bytes 41817268 (41.8 MB)
    RX errors 0  dropped 566  overruns 0  frame 0
    TX packets 50407  bytes 6441592 (6.4 MB)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
    inet 127.0.0.1  netmask 255.0.0.0
    inet6 ::1  prefixlen 128  scopeid 0x10<host>
    loop  txqueuelen 1000  (Local Loopback)
    RX packets 122  bytes 10010 (10.0 KB)
    RX errors 0  dropped 0  overruns 0  frame 0
    TX packets 122  bytes 10010 (10.0 KB)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

And this is the pptpd status:

photon@ubuntu1804:~$ sudo systemctl status pptpd
● pptpd.service - PoPToP Point to Point Tunneling Server
  Loaded: loaded (/lib/systemd/system/pptpd.service; enabled; vendor preset: enabled)
  Active: active (running) since Sun 2021-05-23 07:31:03 +0430; 20s ago
     Docs: man:pptpd(8)
           man:pptpctrl(8)
        man:pptpd.conf(5)
 Main PID: 6466 (pptpd)
    Tasks: 3 (limit: 1107)
   CGroup: /system.slice/pptpd.service
       ├─6466 /usr/sbin/pptpd --fg
       ├─6475 pptpd [5.119.181.36:478E - 0000]
       └─6479 /usr/sbin/pppd local file /etc/ppp/pptpd-options 115200 10.0.0.1:10.0.0.100 ipparam 5.119.181.36 plugin /usr/lib/pptpd/pptpd-logw

May 23 07:31:12 ubuntu1804 pptpd[6475]: CTRL: Starting call (launching pppd, opening GRE)
May 23 07:31:12 ubuntu1804 pppd[6479]: Plugin /usr/lib/pptpd/pptpd-logwtmp.so loaded.
May 23 07:31:12 ubuntu1804 pppd[6479]: pppd 2.4.7 started by root, uid 0
May 23 07:31:12 ubuntu1804 pppd[6479]: Using interface ppp0
May 23 07:31:12 ubuntu1804 pppd[6479]: Connect: ppp0 <--> /dev/pts/1
May 23 07:31:13 ubuntu1804 pppd[6479]: peer from calling number 5.119.181.36 authorized
May 23 07:31:13 ubuntu1804 pppd[6479]: MPPE 128-bit stateless compression enabled
May 23 07:31:14 ubuntu1804 pppd[6479]: Cannot determine ethernet address for proxy ARP
May 23 07:31:14 ubuntu1804 pppd[6479]: local  IP address 10.0.0.1
May 23 07:31:14 ubuntu1804 pppd[6479]: remote IP address 10.0.0.100
Solution

  • After trying many solutions finally I found the answer. My ethernet interface called ens160 so for IP masquerading I should use this:

    sudo iptables -t nat -A POSTROUTING -o ens160 -j MASQUERADE