[Babel-users] Babel instability in WLAN-SI

Juliusz Chroboczek jch at pps.univ-paris-diderot.fr
Mon Dec 14 14:40:46 UTC 2015

Jernej, Mitar,

I think I've found the cause of the instability of Babel in your network.

If I look at the nodewatcher database, I see that there's a number of
wireless links that were incorrectly detected as wired.  For example, if
I look at node urban-1:


I see that most of the links have a TX-cost of 96, which indicates that
the links have been incorrectly detected as wired on the other side.
OTOH, the RX-cost is above 256, which indicates that the node urban-1 has
correctly detected the links as wireless.

This is really bad, since on wired links babeld will disable link quality
estimation and cause the links to go down-up whenever two Hellos are lost
in a row.

You need to find out what's going on; most probably, the radios are behind
a switch, and babeld is unable to detect that they are wireless links.  If
everything else fails, you should enable link estimation manually by saying

  interface eth42 wired false

or by running babeld with the "-w" flag.  (Obviously, this is not
recommended, since doing link quality estimation on wired links is

-- Juliusz

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