How to generate IPv6 RA without any prefixes?

Siquijor Philips siquijorphilips at
Mon Nov 22 02:59:19 UTC 2010

On Fri, Nov 19, 2010 at 4:52 PM,  <sthaug at> wrote:
>> > 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...

Oh I see. I haven't tried this case with FreeBSD configuring RA with
default route info only. So, how your Juniper router coordinate your
DHCPv6 server to inform the hosts or nodes where to get prefix info
since then your router wasn't configured with pinfoflags options? Or
the hosts are just configured with DHCPv6 client informing directly
the DHCPv6 server for IPv6 address info while its default route is
obtainable via RA through SLAAC?

> Steinar Haug, Nethelp consulting, sthaug at


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