Strange Traffic Problem

[Guus Sliepen]

On Fri, Apr 24, 2015 at 03:08:54AM +0800, shikkc wrote:

> There is a single box on our tinc mesh which can be pinged from all hosts,
> but cannot ping any.
[...]
> TCPdump on other machines shows no incoming traffic from this box, but
> TCPdump on this box shows traffic 'exiting' via the tinc tun device. Having
> tried everything I could conceive of, for some reason I decided to start
> mucking with packet sizes. pinging with a data size of 26 bytes (total size
> 34) works perfectly. Any larger size fails.

Have you tried much larger packet sizes, like 1400? It could be that
this node's ISP blocks UDP packets with sizes that are commonly used by
VoIP. Tinc only checks if large UDP packets can be sent, and if so it
will not detect it when small packets get dropped.

You can also try adding the following to the problematic node's
tinc.conf:

TCPOnly = yes

This will force it to communicate via TCP only, hopefully circumventing
the problem.

-- 
Met vriendelijke groet / with kind regards,
     Guus Sliepen <guus at tinc-vpn.org>
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