> So it means with Per link we can get node protection in some cased means it will see both Inequality 1 & 3 if it gets 3 good enough otherwise 1 is a must. Yes I believe per-link LFA is concerned only with inequality 1, if the chosen LFA node happens to have a better path to destination other than via primary next-hop than you'd get the advantage of node protection.
> With Per Link router will do SPF computation for all the prefixes learned through Primary next-hop so in terms of prefix coverage is concerned i don't see any prefix is left for LFA candidate only point is with per link is that all the prefixes with LFA will share the same backup path. Well yes both flavors (per-link/prefix) will try to find a backup path for all prefixes in the link state database. How I understood it is that per-link LFA will not run a full spf calculation which results in less probability of finding an LFA candidate and in addition to that it will select the first available LFA candidate and stop the calculation afterwards (which is fine since it's not concerned with inequality 3 anyways, so whatever it finds first is fine, according to the limited criteria). > In IOS-XR 4.3.1 Cisco introduced rLFA (remote LFA) which when used in conjunction with LDP can greatly enhance coverage by bypassing spots where traffic may loop. Yes I'd definitely recommend rLFA it's the best thing we have currently, however it runs on a fairly new code. We did use te-tunnles as backup paths to get the rLFA behavior manually and it did provide full coverage in ring topologies. But that was prior to migration to safe harbor 4.2.3 as it introduced a bug on this functionality. adam _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
