FreeBSD eats 169.254.x.x addressed packets

[Jeremy Chadwick]

On Tue, Jun 08, 2010 at 02:26:10PM -0400, Stephen Clark wrote:
> On 06/08/2010 02:05 PM, Jeremy Chadwick wrote:
> >On Tue, Jun 08, 2010 at 01:45:59PM -0400, Stephen Clark wrote:
> >>Why does FreeBSD 6.3 eat 169.254.x.x addressed packet when
> >>4.9 didn't?
> >
> >The following output would help:
> >
> >- ifconfig -a
> >- netstat -rn
> >- Contents of /etc/rc.conf
> >
> >Also, be aware that RELENG_6 is to be EOL'd at the end of this year:
> >http://security.freebsd.org/
> >
> Hi Jeremy,
> 
> I am not sure that information is relevant. We have two systems configured
> identically one using 4.9 the other 6.3.

My concern was that someone had botched something up in rc.conf or
during the OS upgrade/migration, resulting in there being no loopback
interface.  I also wanted to verify that your routing table looked
correct for what ifconfig showed.

Other users pointed you to RFC 3927.  Wikipedia has this to say:

http://en.wikipedia.org/wiki/Link-local_address

"Based on RFC 3927, IPv4 uses the 169.254.0.0/16 range of addresses.
However, the first and last /24 subnet (256 addresses each) in this
block have been excluded from use and are reserved by the standard.[1]"

I read this to mean 169.254.0.0/24 and 169.254.255.0/24.

Your previous ifconfig statement shows:

> $ ifconfig rl0
> rl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         options=8<VLAN_MTU>
>         inet 192.168.129.1 netmask 0xffffff00 broadcast 192.168.129.255
>         inet 169.254.1.1 netmask 0xffff0000 broadcast 169.254.255.255
>         ether 00:30:18:ae:7c:77
>         media: Ethernet autoselect (100baseTX <full-duplex>)
>         status: active

With this configuration, you're using both the first and last /24
netblocks -- 169.254.0.0 for your network address, and 169.254.255.255
for your broadcast address.

You should be able to avoid this by using 169.254.1.0/24.

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |