How to generate IPv6 RA without any prefixes?

[sthaug at nethelp.no]

> > In IPv6 it should be possible to generate a Router Advertisement which
> > contains no prefix options (the idea being that I want the host to
> > populate its default router list but nothing else). However, I cannot
> > seem to get rtadvd to do this.
> >
> > If I start rtadvd with no /etc/rtadvd.conf file, it sends RAs with a
> > prefix option corresponding to the IPv6 address of the interface. In
> > the /etc/rtadvd.conf I can explicitly specify prefixes ("addr"), but
> > I can't find any way to specify that no prefix options should be sent.
> >
> > Any suggestions?
> 
> You mean to say that you want your router to act as the default IPv6
> gateway only advertising default route via RA and the IPv6 prefixes
> are managed by other means such as DHCPv6 server?

Correct.

> Because by its the
> only way I can think of with your case now. You can specify
> 'pinfoflags' with 'l' in the /etc/rtadvd.conf to suppress the prefix
> information option being advertised.

Specifying a prefix ("addr") and "pinfoflags" with "l" makes rtadvd send
RAs with a prefix info option option which contains the onlink flag. It
certainly does not suppress the prefix info option.

Specifying a prefix ("addr") and "pinfoflags" without "a" makes rtadvd
send RAs with a prefix info option which does not contain the auto flag
- this prevents SLAAC from taking place.

I would like to get rtadvd to send RAs completely *without* a prefix
info option. My Juniper routers at work can do this just fine...

Steinar Haug, Nethelp consulting, sthaug at nethelp.no