On Mon, Sep 28, 2015 at 08:58:35PM +0100, Israel G. Lugo wrote: > Hello, > > I have a question regarding BIRD's OSPF and summarized networks. Not > sure if I'm doing the right thing. > > I've got access routers running BIRD, configured as ABR between area 0 > and their respective user-facing areas. > > Access networks are VLAN interfaces, e.g. eth0.161. Backbone connection > is a separate physical interface (eth1). > > If the physical access interface (eth0) goes link down for some reason, > BIRD changes the VLAN OSPF interfaces (eth0.161) to Loopback state. It > stops announcing the directly connected prefixes on the VLAN interfaces, > but it keeps announcing a /32 for the interface's IP, with a metric of 0. > > That in itself isn't the problem. It makes sense, as the IP belongs to > the machine. The problem is, if I use the "network" option (to define > summary LSAs), the /32 will be summarized to the entire prefix, making > it be announced again. What's worse, it is now announced with a metric > of 0, which means it will override any redundant routers I might have. > > ... > > I understand that literally, BIRD is doing what I asked it to do: > summarize A.B.C.0/24. As long as it has some valid route inside that > prefix (in this case the /32), it will announce the whole summarized > network, with a metric equal to the largest cost (RFC 2328, 12.4.3). > > It would seem to me, though, that this case warrants special treatment. > The /32 only exists because the interface transited to Loopback state > when it lost the link.
Hello You are right with your analysis of the issue. I agree that in your case it does not make sense, but unfortunately, the behavior is IMHO more or less correct with regard to RFC 2328. I am not sure how it should be modified to be consistent and to make sense in your setting. /32 local definitely should be propagated (at least by default). Perhaps ignoring zero metric /32 from triggering summarization? Or ignoring any local stub network? Or some more general configurable limit for summarization (like minimal cost)? > Is there something I should be doing differently? Or could this perhaps > be a bug, and not intended behavior? Perhaps you could try to use stubnet option with hidden + summary suboptions to hide these /32 routes to not trigger the summary networks. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santi...@crfreenet.org) OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) "To err is human -- to blame it on a computer is even more so."
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