What is EIGRP FD (Feasible Distance) EIGRP Feasible Distance is the cost to the next hop as well as Administrative Distance. What is EIGRP SIA (Stuck In Active) condition EIGRP Stuck in Active is the condition when a route becomes unreachable and not all queries for it are answered. To sum it up, routes generally become SIA when a neighbor either doesn't answer a query, or either the query or reply took a wrong turn somewhere. EIGRP is partially open source routing protocol. The link between the two routers is of low quality, allowing just enough packets through to keep the neighbor relationship intact, but not good enough to allow the replies through. The queried router's memory is corrupt or otherwise unable to allow the router to answer the query. The queried router's resources are unavailable, generally due to high CPU utilization. From experience, I can tell you that troubleshooting SIA routes is more of an art form than a science, but there are four main reasons a route becomes SIA: The link is unidirectional, so the query can't possibly be answered. A route becomes SIA when a query goes unanswered for so long that the neighbor relationship is reset. Sometimes that doesn't happen, though, and the route becomes SIA - Stuck In Active. Generally, a route shown as Active is going to be there for a very short period of time by the time you repeat the command, hopefully that Active route has gone Passive. When a route is Passive ("P), that means it's not being recalculated and it's a usable route. If a route shows as Active in the EIGRP topology table, that means that DUAL is currently calculating that route, and it's currently unusable. That's what we want, right? Active routes sound good, right? Well, they sound good, but they're not. A popular misconception is that we want these routes to have an "A" next to them - so they're active. View the EIGRP topology table with the show ip eigrp topology command, and you'll see a code next to every successor and feasible successor.
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