By default, how frequently does the designated intermediate system (DIS) send out its hello packets?

The designated intermediate system (DIS) in an Open Shortest Path First (OSPF) environment, specifically within a frame relay or ATM network, is responsible for sending hello packets to establish and maintain adjacency with neighboring routers. By default, the DIS sends these hello packets every 3 seconds. This short interval is designed to ensure timely updates and keep neighbor relationships active, which is crucial for the operation of the link-state routing protocol.

The 3-second interval allows the DIS to quickly detect any changes in the network topology or neighbor status, enabling faster convergence of the OSPF network. In operational terms, having a dynamic and responsive hello interval helps maintain robust and resilient network communications, ensuring that all participating devices can react promptly to any network events.