Ondrej Zajicek <santi...@crfreenet.org> writes: >> > Also note that unreachable routing entries should not be propagated to >> > core. >> >> This is actually done to satisfy a requirement of the Babel protocol: >> Temporary blackholing is used to avoid routing loops. Quoting section >> 3.5.5 of RFC6126: >> ... >> Now, if the protocol can't propagate an infeasible route to the core, >> how do I satisfy this requirement? > > Didn't know that. You could propagate the unreachable route in the sense > that it will work. But usually it is not a good idea - e.g. some other > protocol could have regular routes for the same network, or there could > be some covering route. > > BTW, the argumentation in 3.5.5 of RFC 6126 seems a bit strange to me. > It essentially says that unreachable routes are added to avoid transient > routing loops before Babel converges. But transient routing loops until > convergence is a common behavior for IGPs (both RIP, OSPF and IS-IS do > that), while blackholing may be far less expected behavior, esp. if it is > for several minutes, which is far longer time than usually necessary for > protocol convergence. It seems more like local policy setting than > something which should be part of protocol specification.
Hmm, I think Juliusz is probably better at answering that than I am; added to CC... Juliusz, care to weigh in? > It is true that this part is probably not described anywhere in depth. > There are some notes in nest/protocol.h that are not propagated to the > documentation. For the rest, you can use the source, but sometimes > even the source is 'wrong'. Will poke around, thanks. > In that case you have always non-NULL babel_iface.iface and you could > remove some vestigial code from RIP, like: bif->iface ? > bif->iface->name : "(dummy)" Yeah, have already removed that in some places, but some house cleaning is probably needed :) -Toke
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