[Babel-users] A Babel experiment at funkfeuer.at

Harald Geyer harald at lefant.net
Mon Dec 22 17:07:35 UTC 2008


Some small updates:

I compiled and tested babel with the freifunkfirmware and it seems
to worki (without any special configuration included yet). 
The package is available at:


I use something like "babel -g 2222 eth1 sit1" to start babel and
monitor it via "telnet ::1 2222" - do you recommend something else
then telnet? One thing that's also pretty annoying is that the telnet
of freifunkfirmware doesn't support IPv6, so I guess that's my first
feature request: It would be nice if babel would accept connections
on some routable addresses or on

When babel is running on a small router, then it prints messages
"netlink_read: recvmsg(): No buffer space available" every now and
then. It doesn't do that on my work station. After looking it up
in the source I think it is harmless, but just to let you know ...
> Just a little bit.  If your nodes don't have global IPv6 addresses, they
> will be completely invisible in the routing tables (recall that Babel is
> not a link state protocol).  Hence, in order to put some load on the Babel
> network, you will want to give some of your nodes a global IPv6 address.
> You will want to use the following babel.conf:
>   redistribute local ip ::/0
>   redistribute local deny
> This will prevent the local node from redistributing its local addresses,
> but will allow routing of IPv4 if other nodes redistribute their IPv4
> address, so it makes switching to a hybrid network at a later date easier.
> If you want to prevent Babel from routing IPv4, even for other nodes, you
> need to additionally say
>   in ip deny

Ok, I used this as a start. Next I'll play with non default
metrics. Especially tunnels should be expensive instead of having the
same link cost as a cable ... 
> Now the small hack I mentioned: on GRE and OpenVPN interfaces, the kernel
> does not automatically generate an IPv6 address, so you will need to add
> such an address yourself.  I'm attaching a script that fixes that.  You
> will need to install the ahcp-generate-address utility, which you will find
> as part of ahcpd.

So far I have only played with sit tunnels, which works fine. I suggest
that we start with two tunnels between your site and Vienna. The IPs
on our side will be and Just tell me
what IPs you choose on your side and I'll activate the tunnels.


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