BIRD <-> Quagga OSPF Compatibility

Alex Bligh alex at
Wed Nov 2 15:30:38 CET 2011


> I forgot, not everyone uses private addresses :-), It seems that using
> /31 quasi-reqular prefix (RFC 3021) is probably also OK.

Yes. But I can't use those here either :-)

>> What if you forcefully remove the IA_PEER flag for your ppp interfaces?
>> Then an IP address is send instead of ifIndex in the router LSA. Could
>> be an useful addition to bird.
> IA_PEER is not a flag of iface, it is internal BIRD flag (of an address)
> signalizing that there is not a common prefix (it is 'unnumbered').
> So it is not possible to forcibly remove that (outside of BIRD).
> You perhaps mean IFF_POINTOPOINT system iface flag.

That is what I thought you meant.

> Forcibly removing
> it from physically ptp ifaces (like ppp or slip) is not a good idea as
> in that case BIRD would think that these ifaces are physically NBMA and
> does not allow run OSPF in PTP mode on it (just NBMA or PTMP mode).

I don't actually need OSPF to be running on the interfaces in question
in the sense of transmitting packets. Currently I'm doing two things:
* redistributing the interface networks when these are numbered (e.g.
  a /28)
* redistributing the static /32 routes when they are not.

The quagga peer is on a different interface.

Perhaps I read the original report wrong: I had read this as (also)
causing a problem in external LSAs imported into bird on such links,
then reaching Quagga.

> It
> would be possible to run BIRD in PTMP mode on unnumbered iface over
> physically PTP link (PTMP and PTP mode is very similar) but it is
> non-standard (RFC implicitly supposes that PTMP is numbered) so it is
> probably not a good starting point for BIRD-Quagga compatibility (i
> don't have a clue whether and how PTMP mode is implemented in Quagga).

>From days gone by playing with Cisco, OSPF and frame-relay ATM 
interworking, I dimly recall that this (Running on PTMP mode over a PTP 
link) does in fact work, and should work because a single point is a 
degnerate case of multipoint. I don't believe the multipoint standard 
suggests that there has to be more than one endpoint. I do not recall 
trying this unnumbered, and
I agree the RFC probably implicitly prohibits it.

Alex Bligh

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