Hold down timer
(also Holddown)
Hold down timer definition
A hold down timer is a mechanism used in networking, particularly in routing protocols. It’s set to prevent a router from accepting any changes to a particular route for a specified period. Usually, after a route becomes unreachable.
See also: distance-vector routing protocol
History of a hold down timer
The hold down timer emerged in the 1980s with the development of dynamic routing protocols like RIP and OSPF. It addressed the challenges of rapidly changing network topologies. Holddown’s introduction addressed the need for reliable routing in growing, complex networks.
By temporarily suppressing route updates after changes like link failures, hold down timers prevent routing loops and instability. This mechanism allows networks to stabilize and converge before accepting new information. Despite the evolution of networks and protocols, the hold down timer’s core function in maintaining network stability has remained vital.