A high-availability network topology designed and simulated in GNS3 using MikroTik RouterOS. Implements OSPF dynamic routing, VRRP gateway redundancy, and redundant uplinks for automatic failover.
The topology consists of two MikroTik routers in a VRRP active-passive configuration sharing a virtual IP as the default gateway. OSPF advertises routes between routers and downstream switches, with cost metrics tuned to prefer the primary link. A secondary link provides automatic failover with sub-second convergence. GNS3 emulates the full environment for testing failure scenarios.
Default OSPF timers caused ~40-second convergence on link failure, which was too slow for HA requirements. Tuning hello and dead intervals to 1s and 4s respectively reduced failover time to under 5 seconds without excessive overhead.
With default preempt mode enabled, the primary router would reclaim the virtual IP immediately after recovering, causing a brief traffic disruption. Disabling preempt and using a higher priority on the primary achieved a stable active-passive setup.
