What are two possible causes for EIGRP Stuck-In-Active routers? (Choose Two)
A.
Some query or reply packets are lost between the routers.
B.
The neighboring router starts receiving route updates from this router.
C.
A failure causes traffic on a link between two neighboring routers to flow in only one direction
(unidirectional link).
D.
The neighboring router stops receiving ACK packets from this router.
Explanation:
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. Sometimes that doesn´t
happen, though, and the route becomes SIA – Stuck In Active.
A route becomes SIA when a query goes unanswered for so long that the neighbor relationship is
reset. From experience, I can tell you that troubleshooting SIA routes is more of an art form than ascience, but there are four main reasons a route becomes SIA:
The link is unidirectional, so the query can´t possibly be answered. The queried router´s resources
are unavailable, generally due to high CPU utilization. The queried router´s memory is corrupt or
otherwise unable to allow the router to answer the query.
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.
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. I told you it wasn´t the easiest thing to
troubleshoot!