[quagga-dev 5914] Re: OSPF, passive interface question

Joakim Tjernlund joakim.tjernlund at transmode.se
Thu Sep 4 13:36:33 BST 2008


On Thu, 2008-09-04 at 08:23 -0400, Andrew J. Schorr wrote:
> On Thu, Sep 04, 2008 at 09:24:48AM +0200, Joakim Tjernlund wrote:
> > For a passive interface it appears that only incoming hellos are
> > ignored.
> > Should not all incoming messages be ignored on a passive interface?
> 
> In principle, I think it should neither send nor receive any packets
> on a passive interface.  In pursuit of that goal, I think the daemon
> does not join any multicast groups on passive interfaces.
> But yes, I think it should probably ignore all incoming packets.

That was my impression too, but I don't know exactly how
passive interface should react on received pkgs.

> 
> Are you suggesting that ospf_read should check whether the interface
> is passive (rather than in ospf_hello)?  I guess that could make

Yes, if the intention is to ignore everything.

> sense.  Is it likely to receive such packets in the first place,
> given that we are not in the multicast group?

Dunno, but the text pasted by Everton from the Cisco manual makes me
wonder:
.... "the particular subnet will continue to be advertised to other
interfaces, and updates from other routers on that interface continue to
be received and processed."

This suggests to me that passive interfaces should receive as normal.
Now I am confused :(

What is the proper way to publish an subnet much like passive interface
does, but not send or receive OSPF traffic on interfaces that belongs
to that subnet? 

 Jocke



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