[Olsr-users] Routing problem with bad ETX

Michel Blais (spam-protected)
Tue Apr 30 17:21:53 CEST 2013

That normal since 2 up without lost will give you a cost of 2. The 
single up link cost can be tweeked via LinkQualityMult. If you want to 
double de link cost for this link, change LinkQualityMult, for remote ip 
address or default for all the subnet, to 0.5, to triple it change it to 
0.33, etc.


Le 2013-04-30 11:06, Simon Ebnicher a écrit :
> Hi,
> we have set up a small OLSR mesh network with three routers (TP-Link
> TL-WDR3600 running OpenWrt 12.09rc1, olsrd 0.6.3). We placed two routers
> near to each other, and the third router at quite some distance.
> R1 <----ETX:~1----> R2 <---------------ETX: 1.x to 2.x-----------> R3
> The ETX on the direct link between R1 and R3 is usually below 2 (about
> 1.3 to 1.7), so the direct route is preferred. However, the direct route
> is completely unusable for data transfer (e.g., ping reports >95% packet
> loss). As soon as two hop route via R2 is used, ping and other traffic
> works fine.
> We are wondering why the unreliable link is rated too optimistically. We
> suspect that the Hello and TC multicast packets (which are used to
> calculate the ETX) may have a better reception probability than unicast
> packets (e.g., because they are sent at lower rates, no RTS/CTS). This
> would lead to ETX values that do not reflect the link accurately.
> Can anyone confirm or explain this behaviour and maybe offer a solution?
> Best regards,
> Simon Ebnicher

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