To achieve fast reconvergence between directly connected switches in a data center using OSPFv2, two critical actions must be taken. First, setting low OSPF hello and DEAD timers can significantly reduce the time it takes for OSPF to detect a link failure and start the reconvergence process. This is because OSPF hello packets are used to maintain neighbor relationships, and the DEAD timer determines how long a router will wait without receiving a hello packet before declaring the neighbor down. By reducing these timers, OSPF can detect failures more quickly and initiate a faster reconvergence.
Second, enabling Bidirectional Forwarding Detection (BFD) for failure detection is essential. BFD is a network protocol that provides fast failure detection times for all media types, encapsulations, topologies, and routing protocols. By implementing BFD, OSPF can be notified of link failures almost immediately, allowing for a rapid response to changes in the network topology and ensuring minimal disruption to data flows2.
References := IP Routing: OSPF Configuration Guide - OSPFv3 Fast Convergence