OSPF anycast prefix being filtered

[Patrik Lundin]

On Fri, Apr 10, 2015 at 11:29:24AM +0200, Ondrej Zajicek wrote:
> On Fri, Apr 10, 2015 at 10:23:23AM +0200, Patrik Lundin wrote:
>
> > 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.
> 
> Just add 'dummy' to /etc/modules, it will be loaded and dummy0 will be
> created by default.
> 

Ah, this explains why my current solution was creating an extra dummy1
interface, I did not realize just loading the module would create
dummy0. Thanks for the tip!

> > * 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.
> 
> That is because OSPFv2 uses IPv4 addresses where /31 signalize ptp link
> and /32 stub link, OSPFv3 uses IPv6 link-local addresses and there is
> /64 everywhere.
> 

Good to know, I was mostly pointing it out if anyone was wondering why
my configuration differed somewhat between the protocols.

> > 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!
> 
> There are two possibilities:
> 
> 1) Shut down dummy interface (ip link set dummy0 down), OSPF should
> immediately stop propagating attached addresses. This is probably the
> cleanest solution. You could even have multiple dummy interfaces with
> different addresses for different services and disable them
> independently.
> 
> 2) Shut down OSPF protocol (birdc disable ospf1), OSPF would immediately
> de-peer. It should be also immediate, although in unusual cases you have
> to wait for timeout.
> 

Thanks for the ideas, once I have a second node available for testing
I'll experiment with these solutions.

Regards,
Patrik Lundin