Addressing looks correct and hellos are present, but adjacency never reaches Full because database exchange fails on MTU mismatch.
NetworkAdvanced
OSPF neighbors remain in ExStart
Connectivity exists and hellos are exchanged, yet database negotiation never completes because DBD packets carry an MTU mismatch across the tunnel.
NetworkIntermediate
OSPF neighbors stay in two-way on shared segment
The state is treated as an outage even though the design role expectations for a multi-access segment were misunderstood.
NetworkIntermediate
A failover test appears healthy until traffic returns to the primary HSRP router and static ARP state on one path keeps forwarding from fully recovering
Community-field network problem inspired by Cisco Community cases where HSRP failover worked but failback exposed stale static ARP behavior.