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Orazio edited this page Oct 30, 2020 · 30 revisions

FAQ (Frequently Asked Questions)

Links to protocol specific FAQs

How do I troubleshoot connection issues?

Preliminary checks

  • Confirm that all checks are [OK] using pivpn -d.

In our case:

$ pivpn -d
[...]
::::		Self check		 ::::
:: [OK] IP forwarding is enabled
:: [OK] Iptables MASQUERADE rule set
:: [OK] OpenVPN is running
:: [OK] OpenVPN is enabled (it will automatically start on reboot)
:: [OK] OpenVPN is listening on port 1194/udp
=============================================
[...]

If your debug log shows some [ERR], accept the [Y/n], run pivpn -d again and verify that all checks pass. If not, stop here and look up the error (if you get any) among existing issues or open a new issue.

  • Verify that the server is running.
    • OpenVPN, restart the server with sudo systemctl restart openvpn, run pivpn -d and confirm that the snippet of the server log ends with Initialization Sequence Completed.
    • WireGuard, restart the server with sudo systemctl restart wg-quick@wg0. Run lsmod | grep wireguard and confirm that you get at least this output (numbers don't matter).
wireguard             225280  0
ip6_udp_tunnel         16384  1 wireguard
udp_tunnel             16384  1 wireguard
  • Acquire the installation settings using cat /etc/pivpn/wireguard/setupVars.conf if using WireGuard or cat /etc/pivpn/openvpn/setupVars.conf if using OpenVPN.
[...]
IPv4dev=eth0                  <--- Network interface you have chosen

IPv4addr=192.168.23.211/24    <--- IP address of the Raspberry Pi at the time of installation
                                   (only consider the 192.168.23.211 part)

IPv4gw=192.168.23.1           <--- Gateway IP, which you will type into a web browser to open
                                   the management interface

pivpnPROTO=udp                <--- Protocol you need to use in the port forwarding entry

pivpnPORT=1194                <--- Port you need to forward

pivpnHOST=192.0.2.48          <--- Public IP or DNS name your clients will use to connect to
                                   the PiVPN
[...]
  • Check that the current IP address of the interface IPv4dev is the same as IPv4addr. You can see the current IP with ip -f inet address show IPv4dev.

In our case:

$ ip -f inet address show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    `inet 192.168.23.211/24 brd 192.168.23.255 scope global dynamic eth0
       valid_lft 84694sec preferred_lft 84694sec

Confirmed: 192.168.23.211 is the same as the content of the IPv4addr variable.

If it's not the same, go to your router admin webpage and reserve the static IP IPv4addr to the MAC address of the IPv4dev interface. To show the MAC address: cat /sys/class/net/IPv4dev/address. Then reboot the Raspberry Pi.

  • Check that the current public IP of your connection is the same as pivpnHOST. To check the current public IP: curl -s https://checkip.amazonaws.com.

In our case:

$ curl -s https://checkip.amazonaws.com
192.0.2.48

Confirmed: 192.0.2.48 is the same as the content of the pivpnHOST variable.

If the IP is different, then update the IP using the OpenVPN or WireGuard guide. If your IP changes frequently, the norm on most home connections, consider using a Dynamic DNS.

If you are already using a DDNS, and thus pivpnHOST contains your domain name, use dig +short yourdomain.example.com to check whether the returned IP matches curl -s https://checkip.amazonaws.com.

Packet capture

We will use tcpdump take a peek into the network interface to see if packets are reaching our Raspberry Pi.

First off, if you want to test the connection using your smartphone as a client, make sure to use MOBILE DATA, do not test from the same network where the Raspberry Pi is located. If you want to use a PC, connect to the internet via TETHERING/HOTSPOT.

Connecting from the same network as the server not only doesn't make sense (you are already inside the network the VPN is supposed to connect you to) but may not work with many routers.

From your device, go to https://ipleak.net and check what's your IP address, let's say we have 192.0.2.45.

  1. Open a root shell: sudo -s
  2. Install tcpdump: apt install tcpdump -y
  3. Run tcpdump -n -i IPv4dev pivpnPROTO port pivpnPORT (it will block the terminal but don't worry)
  4. Try to connect from your device
  5. Shortly after you should see some packets being exchanged between your Raspberry Pi and your device

In our case:

# tcpdump -n -i eth0 udp port 1194
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
10:57:38.952503 IP 192.0.2.45.28050 > 192.168.23.211.1194: UDP, length 32    <--- Your device sent a packet to the Raspberry Pi
10:57:49.109202 IP 192.168.23.211.1194 > 192.0.2.45.28050: UDP, length 128   <--- Your Raspberry Pi responded to your device
10:57:49.144774 IP 192.0.2.45.28050 > 192.168.23.211.1194: UDP, length 128
10:57:59.490185 IP 192.168.23.211.1194 > 192.0.2.45.28050: UDP, length 32

You are looking at udp or tcp packets coming to your Raspberry Pi on the port you specified, via the network interface (ethernet or wifi) you chose. The example output above is a successful conversation.

Here's an unsuccessful one (no packets reach the Raspberry Pi):

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
  1. Press CTRL-C to stop the capture
  2. Exit the root shell: exit

What to do if I see no packets?

  • If you set up PiVPN with ethernet and later switched to wifi, you will have a different IP. Easiest way to fix is to reinstall and pick the new network interface.
  • Check if your ISP uses Carrier-grade NAT (check online). With CGNAT, your router gets a private IP, making port forwarding ineffective. This is mostly the norm if your router connects via 4G/LTE. If that's the case, you need to ask the ISP for a public IP.
  • If you see packets coming, but no response from the Pi, it may indicate routing issues, attempts to block the connection (on either side), or poor connectivity. In all cases, try to connect from a different network.
  • You may have misconfigured firewall rules on your Pi, open an issue and add the output of sudo iptables -S and sudo iptables -t nat -S.

If you performed all the following steps and suggestions, but you still can't connect, open a new issue showing all the steps you followed to troubleshoot. Include the packet capture as well (censor client IPs if you want). Remember to follow the ISSUE TEMPLATE.

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