EIGRP Stuck in Active

  • If EIGRP loses an interface and there is no feasible successor route in the topology table, queries will be sent to all EIGRP neighbors to see if a backup route exist to the lost subnet in the wider network.
  • Router sending the queries must wait until it has heard responses to said query from ALL it’s neighbors before it installs any newly learned backup route into the routing table. Until all queries are responded to, the route is said to be “stuck in active” or SiA.
  • Queries are cascaded from receiving neighbors on to their all their other EIGRP  neighbors resulting in a potential flood of queries across an entire network.
  • There is a default timer of three minutes set by the original querying router.  If it does not receive an answer to all queries within this period, it resets all it’s neighbor relationships which will reset the SiA state but is obviously intrusive.
  • The scope of query can be limited by either the use of EIGRP STUB (the router with the missing route will not even query a stub) or by means of a SUMMARY ROUTE whereby the neighbor with the summary will immediate reply that it has no additional route to the lost subnet.

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