Hello Sameh
The hold or holddown timer is a timer that expires when new hello or any EIGRP packets are received from a particular EIGRP neighbor. By default it is set to 15, and counts down to 0. Every time a hello or any other EIGRP packet is received form a particular neighbor, this timer is reset. If 15 seconds pass without any EIGRP packets arriving from that particular neighbor, the neighbor adjacency is dropped.
The Stuck in Active state is a situation where an EIGRP router doesn’t receive any replies to query packets from a neighbor. If the time in stuck in active exceeds 3 minutes, the neighbor adjacency is dropped. During SIA, hello packets are still exchanged between neighbors so the holddown timer doesn’t expire.
SIA doesn’t mean that neighbors can’t communicate. It simply means that a response to a particular query has not been received. SIA can occur for several reasons, and is further described in the following lesson:
I hope this has been helpful!
Laz