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

Juliusz Chroboczek jch at pps.jussieu.fr
Mon Dec 15 19:28:38 UTC 2008

> Sure, but since in Vienna olsr manages IPv4 and only IPv4 why not use
> babel together with IPv6? That way I don't need to worry about how to
> claim some IPv4 subnet for babel

Now I come to think about it -- yes, it's a good idea.

> and I don't need to configure addresses on all nodes participating in the
> experiment: Just install babel + some special config file and it will
> route via IPv6 link local addresses by default. Just install some gobal
> addresses on nodes used for monitoring.  Is that too simple?

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

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.

Have fun,


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