Advanced IP Network Design (CCIE Professional Development)

Case Study: Retransmissions and SIA

Two timers that can interact in EIGRP to cause a SIA route in EIGRP are the SIA timer and the hold timer between two peers. But how do these two relate? This section looks at the two independently and then it looks at how they interact.

The Hold Timer

The obvious use for the hold timer is to determine how long you will holdup a neighbor relationship without hearing any EIGRP hellos. Each time a router receives a hello packet from a neighbor, it resets the hold timer to the hold time contained in the hello packet and decrements it once for each second that passes.

Once the hold timer reaches zero, the neighbor is assumed dead. All paths through that neighbor are marked unusable (DUAL is run over these destinations ...