How to enable IPv6 on a subset of interfaces
jhell at DataIX.net
Wed Jan 13 12:02:10 UTC 2010
On 1/12/2010 7:42 PM, David Horn wrote:
> On Tue, Jan 12, 2010 at 4:36 PM, Brett Lee <Brett.Lee at sun.com> wrote:
>> Using FreeBSD 8.0-RELEASE, and am trying variations in /etc/rc.conf in an
>> attempt to enable IPv6 on ONLY one of the systems two interfaces.
>> Specifically, em0 should be enabled IPv4 DHCP, and bge0 should be enabled
>> IPv6 only.
>> From the KAME link below, and the files /etc/network.subr and
>> /etc/defaults/rc.conf, am reading that "ipv6_network_interface" should work;
>> however the following still results in em0 obtaining IPv6 addresses:
>> In another attempt (see link below), it looks like "ifconfig_em0" may
>> support a "NOIPV6" param, but in practice it doesn't seem to work for me:
>> ifconfig_em0="DHCP NOIPV6"
>> Am hopeful that someone might point out how I could enable this
>> Thanks in advance! -Brett
> NOIPV6 is not a valid rc.conf configuration token at this time.
> I am assuming that you are using SLAAC for IPv6 prefix/address
> distribution (via rtadvd/radvd), and not DHCPv6.
> ipv6_network_interfaces is the correct rc.conf(5) variable to use to
> specifically control which interface gets configured using SLAAC via
> rtsol(8), but will not stop other interfaces from getting the RA
> (Router Advertisement) packet which starts IPv6 SLAAC (Stateless
> In -current/9.0 there are nice new ifconfig parameters (inet6
> ifdisabled -nud -accept_rtadv) and rc.conf variables that do just what
> you are looking for, but they are not in 8.0 at this time.
> In 8.0 you can use the ndp(8) utility to set the -accept_rtadv (and/or
> ifdisabled/nud,etc.) flags on a per-interface basis. The
> "-accept_rtadv" flag will disable SLAAC for the specified interface,
> but must be called before the interface gets the "RA" packet to be
> You can do an ugly *unsupported hack* in 8.0 to call ndp from within
> rc.conf/rc.d startup scripts until the new code makes it into a
> ifconfig_em0="DHCP `ndp -i em0 ifdisabled -nud -accept_rtadv >/dev/null 2>&1`"
> This will cause some boot-time error messages about not finding ndp
> (before /usr is mounted), but these can be ignored, as the backticked
> ndp line will be run EVERY time that rc.conf is sourced. This is
> just a work-around for 8.0 that happened to work for me at the time.
> If someone else has a better solution that fits properly within the
> confines of rc.conf, please speak up.
Not sure if 8.0 still has this cap but you could put you interface
commands in /etc/start_if.em0 /etc/start_if.bge0.
If this works out let me know I would be interested since it seems like
a better idea rather than trying to set some weird options inside some
> While on the subject, I have been thinking about putting together a
> patchset to experiment with adding some improved logic surrounding
> using DHCPv6 vs DHPCPv4 vs SLAAC/RTSOL in the rc.conf scripts and
> adding M+0 flag support +rdnss (RFC 5006) support to the kernel and
> userland and devd. If I can ever get a working prototype, I will
> share to get some feedback.
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