Frequently Asked Questions

If you have a common problem or question, you will probably be able to find an answer here. If it is not here, and even the documentation is of no help, please contact the authors.

  1. Frequently Asked Questions
  2. Error messages
    1. Bogus data received
    2. Cannot ping the other node(s)
    3. File descriptor in bad state
    4. Packets looping back to us
  3. Platform specific questions
    1. Error while writing to Generic BSD tap device /dev/tap0: Input/output error on MacOSX or *BSD
    2. Is there an app for tinc?
  4. Generic questions
    1. Why tinc?

Error messages

Bogus data received

Jan 1 12:00:00 host[1234]: Bogus data received from node (

Tinc tries to connect to another node but reports that bogus data has been received. This problem is almost always caused by a problem with the RSA keys from one of the nodes. Check that there is only one key in each rsa_key.priv and in each host config file. Also make sure that the host config files with the same name contain the same key on both nodes. When in doubt, remove the rsa_key.priv files, remove the public keys from the host config files, generate new keys and distribute them again.

Cannot ping the other node(s)

PING ( 56(84) bytes of data.
From icmp_seq=1 Destination Net Unknown

Or when logging with debug level 5:

Jan 1 12:00:00 host[1234]: Cannot route packet from node (MYSELF): unknown IPv4 destination address

When trying to ping another node, it can happen that there is no response. First, check that the other node is really online, and that tinc has made a connection with it. When running tinc in router mode (which is the default), check that the node you are trying to reach has a Subnet statement in its host config file that contains the IP address you are trying to reach.

File descriptor in bad state

Jan 1 12:00:00 host[1234]: Error while reading from ethertap device: File descriptor in bad state

There is a problem reading packet from the virtual network device. Check that the tun module is loaded, and that tinc tries to open the right device file. If you have added Device and/or Interface statements to tinc.conf, try removing them, tinc’s defaults usually work fine.

Packets looping back to us

Jan 1 12:00:00 host[1234]: Packet with destination is looping back to us!

A packet is received from the tapdevice, and tinc tries to send it to the right destination, but finds out that this packet should be send to itself. Chances are that a “Subnet = …” line in the host configuration file of this tinc daemon is wrong. Change it to a subnet that is accepted locally by another interface, or if that is not the case, try changing the prefix length into /32.

Platform specific questions

Error while writing to Generic BSD tap device /dev/tap0: Input/output error on MacOSX or *BSD

tinc needs to be running before configuring the network interface. Try assigning a static ip address, while tinc is running:

ifconfig tap0 <ip address>

If you are still having trouble, check that you have the tun/tap devices installed and configured for your kernel.

Is there an app for tinc?

Tinc itself supports many platforms. Code was merged in version 1.0.10 that in principle allows tinc to run on iPhone and iPod devices. However, as far as we know, no one has created an iOS app for tinc. The latest version in the git repository allows tinc to be compiled for Android. There is an unofficial Android app for tinc that can be found on Google Play.

Generic questions

Why tinc?

Question: I’ve been using VPNs in a production environment, and until now that has been with FreeS/WAN. I would like to know what the differences are between tinc and FreeS/WAN.

Here’s what we think of that:

Other reasons to use tinc instead of other solutions: