[OLSR-users] Problems when losing one link in a dual link setup

[Andreas Tønnesen]

Roar,

Thanks for the feedback.

Roar Bjørgum Rotvik wrote:
> But when LAN is down, I think OLSRD should change the route for 
> 10.10.10.2 to use interface eth1 as soon as possible, but I guess that 
> OLSRD need to wait for 3 lost HELLO packets before the link is 
> determined to be down and may recalculate the routing tables?
> In this special case it should perhaps be possible for olsrd to detect 
> that the cable is unplugged right away, but that would not help if both 
> interfaces is WLAN..

I think adding physical link checking of this kind is to special purpose
to be added in olsrd. This is the price you pay for using a high
interval _and_ a 3*interval validity time. What you can do is to
decrease the validity time. Packet loss is not very likely on Ethernet 
interfaces(to the same degree as bad quality WLAN links), so using
a validity time of 2*interval or even close to 1*interval should give
you a more dynamic change without extra overhead.

> I also saw some inconsistencies in what interface was used as default.
> a) When starting olsrd on two nodes with WLAN connected and LAN cable 
> disconnected, eth1 (WLAN) was used as interface for both LAN and WLAN IP 
> addresses for the other node.
> eth0 (LAN) was configured to be the main interface on both nodes.
> 
> b) When inserting the LAN cable, WLAN interface was still used.
> I had hoped that olsrd would change to LAN interface as it is configured 
> as main interface (I thought I saw this one time, but are not sure).

If interfaces go down and back up, the main address can change. I'm
not sure that is what happened here, but it sounds likely. However,
olsrd is supposed to detect WLAN interfaces and add an extra weight
(internally) so that Ethernet interfaces are prefered when setting
up links. I'll put this on my to-check list :)

- Andreas

-- 
Andreas Tønnesen
http://www.olsr.org