Configure OSPF on two core switches

Configure each core switch with a unique router ID, assign IPs to routed interfaces, define OSPF areas, and ensure consistent OSPF settings across both switches for redundancy and load balancing.Key ConsiderationsRouter IDs and IP Addressing Each core switch must have a unique OSPF router ID. Assign IP addresses to all routed interfaces or VLAN interfaces that will participate in OSPF. If using MLAG or stacked switches, each physical switch still requires its own router ID, even if VLAN interfaces share a virtual IP .OSPF AreasBackbone Area (Area 0): All core switch interfaces connecting to other areas or distribution switches should be in Area 0.Optional Non-Backbone Areas: If you have distribution or access layers, define additional areas and summarize routes into Area 0 to reduce LSDB size .Interface ConfigurationConfigure OSPF on each interface that connects to other OSPF neighbors.Avoid running OSPF over inter-chassis links (ICL) in MLAG setups; use front-panel ports for OSPF adjacencies to prevent unnecessary traffic on the ICL .For routed VLANs, assign the VLAN interface to the appropriate OSPF area and enable OSPF on that interface .Redundancy and Load BalancingEach core switch runs its own OSPF instance, providing redundancy if one switch fails .Use Equal-Cost Multi-Path (ECMP) if supported to balance traffic across multiple links between core and distribution switches .Ensure consistent OSPF configuration across both switches to prevent routing loops or suboptimal paths.Default Routes and RedistributionConfigure default route origination if the core switches connect to an upstream router or firewall.Redistribute connected subnets or static routes as needed to advertise them into OSPF .Example Configuration Steps (Cisco/Generic)CodeCopyrouter ospf 1 router-id 1.1.1.1 ! Unique ID for Core-1 network 10.0.0.0 0.0.0.255 area 0 network 10.0.1.0 0.0.0.255 area 0exitinterface vlan 10 ip address 10.0.0.1 255.255.255.0 ip ospf 1 area 0exitinterface vlan 20 ip address 10.0.1.1 255.255.255.0 ip ospf 1 area 0exit Repeat similar steps on Core-2 with a different router ID and interface IPs.VerificationUse show ip ospf neighbor to verify OSPF adjacencies.Use show ip route ospf to confirm routes are learned correctly.Check for consistent OSPF metrics and area assignments to ensure proper failover and load balancing. By following these steps, both core switches will participate in OSPF independently, maintain redundancy, and provide stable routing for the network while avoiding loops in MLAG or stacked configurations .