OSPF anycast prefix being filtered

[Patrik Lundin]

On Wed, Apr 1, 2015 at 5:12 PM, Ondrej Zajicek <santiago at crfreenet.org> wrote:
> On Wed, Apr 01, 2015 at 05:01:01PM +0200, Patrik Lundin wrote:
>>
>> I specifically noticed that OSPF is supposed to create routes for its
>> own interfaces.
>
> Yes it is supposed to do that. Although handling of 'lo' is kind of
> special case and in some circumstances does not work as expected. In that
> case it is often useful to try dummy interface instead of lo interface.
>

I thought I should report back on my continued adventures. Like you said using
the lo interface seemed to work for IPv4, but I noticed bird6 would
not pick up a
/128 prefix assigned to lo in the same way.

I found this had been discussed earlier:
http://marc.info/?l=bird-users&m=130087394302820&w=2

Because of this I decided to abandon the use of lo altogether, and
just use dummy
interfaces which worked fine for both protocols.

My configuration now looks like this:

Address configuration:
===
# cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback
up ip link add type dummy
up ip link set dev dummy0 up
up ip addr add xxx.xxx.xxx.xxx/32 dev dummy0
up ip addr add yyyy:yyyy:yyyy:yyyy::yyyy/128 dev dummy0

# The primary network interface
auto eth0
iface eth0 inet dhcp
===

bird configuration:
===
# cat /etc/bird/bird.conf
router id zzz.zzz.zzz.zzz;

protocol device {}

protocol ospf {
    import none; # Default is import all
    area 0.0.0.0 {
        interface "eth0" {
            authentication cryptographic;
            password "pass";
        };
        interface "dummy0" {};
    };
}
===

bird6 configuration:
===
# cat /etc/bird/bird6.conf
router id zzz.zzz.zzz.zzz;

protocol device {}

protocol ospf {
    import none; # Default is import all
    area 0.0.0.0 {
        interface "eth0" { type ptp; };
        interface "dummy0" { stub; };
    };
}
===

Some things to note:

* I have not decided on the best way to create the dummy interfaces,
the solution above
was just a quick hack but it seems to work well.

* While bird defaults to a "ptp" link type for eth0, bird6 defaults to
"broadcast".

* The dummy0 interface defaults to being a stub interface in bird,
while it requires
configuration in bird6.

The above configuration works well, the main thing I am still not sure
about if is there is
a "best" way to take a specific anycast node out of rotation if it
needs maintenance. Anyone
have any experience with this? General ideas are appreciated as well!

>> It turns out the "filtered out" messages were not relevant to my problem.
>> The issue was caused by a OSPF network type mismatch. While I was
>> using the BIRD default of point-to-point, the upstream router was
>> configured for broadcast. After the upstream router was changed to use a
>> point-to-point network type everything started to work.
>>
>> It would be nice to know what the meaning of the "filtered out" lines are,
>> but they do not seem to affect the route announcement.
>
> 'filtered out' lines are related to 'import none', e.g. routes were not
> imported from OSPF to master routing table.
>

Thank you for the information!

Regards,
Patrik Lundin