>> 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.
Yes. Babel is designed to be robust not only on wired networks (where OSPF and IS-IS work just fine), but also on wireless mesh networks, where a routing loop, even a transient one, causes cross-link interference and may prevent the routing protocol from reconverging. For that reason, Babel prefers to blackhole rather than risking to create a routing loop. >> It seems more like local policy setting than something which should be >> part of protocol specification. I agree, it could perhaps be disabled on some kinds of links. -- Juliusz
