EIGRP SIA timers

Each EIGRP router manages its own SIA timer. For each route in the ACTIVE state, when the timer reaches 90 seconds, it will send an SIA-QUERY to the corresponding neighbor. If no response (SIA-REPLY) is received, the router sends additional SIA-QUERYs at 90-second intervals until the timer reaches 270 seconds (4.5 minutes).

If a neighbor fails to respond by the end of this 270-second period, the neighbor is considered unresponsive, and **the adjacency is reset. All other routes learned from that neighbor are also removed. This occurs even if Hellos are still being received from the particular neighbor.

The Hello mechanism ensures basic connectivity with neighbors, while the SIA mechanism ensures timely updates and responsiveness for EIGRP routes. The SIA Query and Reply feature helps resolve EIGRP issues not only caused by network congestion but also delays in responding to queries in larger EIGRP topologies.

See also: EIGRP - SIA Process and RTP retry attempts.