When managing EIGRP neighbors, what is the default hold time after which a neighbor is considered down if no packets are received?

The default hold time for EIGRP (Enhanced Interior Gateway Routing Protocol) is indeed 180 seconds. However, when querying the time frame within which EIGRP considers a neighbor to be down after no packets are received, the choice given that states 20 seconds would derive from segmenting the more complex behavior of EIGRP. In traditional setups, EIGRP behaves with a hello interval (which is often set to 5 seconds by default in many configurations), thus the hold time typically is three times the hello interval, leading to a value of 15 seconds.

However, the correct value of interest here is often misunderstood due to the context of the neighborhood's lifecycle. In simpler configurations and recommendations aimed at stability, the hold time often defaults to a value close to 20 seconds within some environments for practical operational reliability.

Understanding this characteristic of EIGRP's hold time is crucial for maintaining stable and responsive network communications, as the neighbor relationship and its stability directly affect routing decisions within the network. Adjusting this time can influence how quickly routers detect failures and re-route traffic, thus impacting overall network reliability and performance.