OSPF Lab Series

In earlier parts of this series, we designed, configured, and optimized IPv4 routing using OSPFv2 across single-area and multi-area topologies. This post transitions to native IPv6 routing using OSPFv3 (RFC 5340) on Nokia SR OS. OSPFv3 decouples protocol operations from IPv4 addressing semantics. It runs on a per-link basis rather than a per-subnet basis, negotiates adjacencies over IPv6 Link-Local addresses, and introduces separate Link-State Advertisement (LSA) types to decouple topological structure from IP prefix reachability. ...

In earlier parts of this series, we focused on establishing reachability, navigating LSDB mechanics, and enforcing boundary rules across different area types. With that foundation in place, this post shifts focus toward optimizing control plane scalability and traffic steering across a multi-area topology. Without route summarization, any localized link flap inside a non-backbone area forces re-computations and updates across the entire backbone. At the same time, relying on default OSPF reference bandwidth settings leaves modern high-speed links evaluated at identical costs, preventing accurate path selection. ...

Building on the single-area baseline from Part 2, this post covers segmentation of the network into multiple OSPF areas, introduces Autonomous System Boundary Routers (ASBRs) for external route redistribution, and covers Stub, Totally Stubby, NSSA, and Totally NSSA area types with LSDB analysis at each stage. SR OS Version: 25.7.R1 CLI Mode: MD-CLI (Model-Driven CLI) Multi-Area Configuration To transition into a multi-area design, we use R2 (PE1) and R5 (PE2) as our Area Border Routers (ABRs) to connect their respective edge customer networks to the Area 0 backbone: ...

This part covers Single-Area OSPFv2 (Area 0) configuration across the 6-node Nokia SR OS topology, verification of neighbor adjacencies, route table population, and LSDB behavior with point-to-point and broadcast network types. SR OS Version: 25.7.R1 CLI Mode: MD-CLI (Model-Driven CLI) Configuration Enable OSPF instance 0 in Area 0 across all nodes. Configure physical and system interfaces as point-to-point, set system interfaces as passive to advertise loopback reachability without sending unnecessary Hello packets, and secure adjacencies with MD5 authentication. ...

In this guide, we establish a 6-node Nokia SR OS baseline in Containerlab and configure the physical interfaces, /30 point-to-point subnets, and system loopbacks required prior to enabling OSPF. SR OS Version: 25.7.R1 CLI Mode: MD-CLI (Model-Driven CLI) Containerlab Topology File (topology.clab.yml) name: OSPF-Lab topology: defaults: kind: nokia_srsim image: localhost/nokia/srsim:25.7.R1 type: sr-1 license: license/license.txt nodes: r1: mgmt-ipv4: 172.20.20.9 r2: mgmt-ipv4: 172.20.20.2 r3: mgmt-ipv4: 172.20.20.3 r4: mgmt-ipv4: 172.20.20.4 r5: mgmt-ipv4: 172.20.20.5 r6: mgmt-ipv4: 172.20.20.6 links: # --- CE to PE Links --- - endpoints: ["r1:1/1/c1/1", "r2:1/1/c1/1"] - endpoints: ["r5:1/1/c1/1", "r6:1/1/c1/1"] # --- Core Links --- - endpoints: ["r2:1/1/c2/1", "r3:1/1/c1/1"] - endpoints: ["r2:1/1/c3/1", "r4:1/1/c1/1"] - endpoints: ["r3:1/1/c2/1", "r5:1/1/c2/1"] - endpoints: ["r4:1/1/c3/1", "r5:1/1/c3/1"] Addressing Plan System (Loopback) Interfaces Node System IP Address Prefix Length R1 10.100.1.1 /32 R2 10.100.1.2 /32 R3 10.100.1.3 /32 R4 10.100.1.4 /32 R5 10.100.1.5 /32 R6 10.100.1.6 /32 Physical Interfaces Router R1 Interface Name Port ID IPv4 Address Prefix Length Subnet Neighbor toR2 1/1/c1/1 192.168.12.1 30 192.168.12.0/30 R2 (PE1) Router R2 Interface Name Port ID IPv4 Address Prefix Length Subnet Neighbor toR1 1/1/c1/1 192.168.12.2 30 192.168.12.0/30 R1 (CE1) toR3 1/1/c2/1 192.168.23.1 30 192.168.23.0/30 R3 (P1) toR4 1/1/c3/1 192.168.24.1 30 192.168.24.0/30 R4 (P2) Router R3 Interface Name Port ID IPv4 Address Prefix Length Subnet Neighbor toR2 1/1/c1/1 192.168.23.2 30 192.168.23.0/30 R2 (PE1) toR5 1/1/c2/1 192.168.35.1 30 192.168.35.0/30 R5 (PE2) Router R4 Interface Name Port ID IPv4 Address Prefix Length Subnet Neighbor toR2 1/1/c1/1 192.168.24.2 30 192.168.24.0/30 R2 (PE1) toR5 1/1/c3/1 192.168.45.1 30 192.168.45.0/30 R5 (PE2) Router R5 Interface Name Port ID IPv4 Address Prefix Length Subnet Neighbor toR3 1/1/c2/1 192.168.35.2 30 192.168.35.0/30 R3 (P1) toR4 1/1/c3/1 192.168.45.2 30 192.168.45.0/30 R4 (P2) toR6 1/1/c1/1 192.168.56.1 30 192.168.56.0/30 R6 (CE2) Router R6 Interface Name Port ID IPv4 Address Prefix Length Subnet Neighbor toR5 1/1/c1/1 192.168.56.2 30 192.168.56.0/30 R5 (PE2) Configuration Router R1 (CE1) edit-config global /configure system name "R1 (CE1)" /configure card 1 card-type iom-1 /configure card 1 mda 1 mda-type me6-100gb-qsfp28 /configure port 1/1/c1 connector breakout c1-100g /configure port 1/1/c1 admin-state enable /configure port 1/1/c1/1 admin-state enable /configure port 1/1/c1/1 ethernet mode hybrid /configure router interface "system" admin-state enable /configure router interface "system" ipv4 primary address 10.100.1.1 /configure router interface "system" ipv4 primary prefix-length 32 /configure router interface "toR2" admin-state enable /configure router interface "toR2" ipv4 primary address 192.168.12.1 /configure router interface "toR2" ipv4 primary prefix-length 30 /configure router interface "toR2" port 1/1/c1/1:0 commit Router R2 (PE1) edit-config global /configure system name "R2 (PE1)" /configure card 1 card-type iom-1 /configure card 1 mda 1 mda-type me6-100gb-qsfp28 /configure port 1/1/c1 connector breakout c1-100g /configure port 1/1/c2 connector breakout c1-100g /configure port 1/1/c3 connector breakout c1-100g /configure port 1/1/c1 admin-state enable /configure port 1/1/c2 admin-state enable /configure port 1/1/c3 admin-state enable /configure port 1/1/c1/1 admin-state enable /configure port 1/1/c1/1 ethernet mode hybrid /configure port 1/1/c2/1 admin-state enable /configure port 1/1/c2/1 ethernet mode hybrid /configure port 1/1/c3/1 admin-state enable /configure port 1/1/c3/1 ethernet mode hybrid /configure router interface "system" admin-state enable /configure router interface "system" ipv4 primary address 10.100.1.2 /configure router interface "system" ipv4 primary prefix-length 32 /configure router interface "toR1" admin-state enable /configure router interface "toR1" ipv4 primary address 192.168.12.2 /configure router interface "toR1" ipv4 primary prefix-length 30 /configure router interface "toR1" port 1/1/c1/1:0 /configure router interface "toR3" admin-state enable /configure router interface "toR3" ipv4 primary address 192.168.23.1 /configure router interface "toR3" ipv4 primary prefix-length 30 /configure router interface "toR3" port 1/1/c2/1:0 /configure router interface "toR4" admin-state enable /configure router interface "toR4" ipv4 primary address 192.168.24.1 /configure router interface "toR4" ipv4 primary prefix-length 30 /configure router interface "toR4" port 1/1/c3/1:0 commit Router R3 (P1) edit-config global /configure system name "R3 (P1)" /configure card 1 card-type iom-1 /configure card 1 mda 1 mda-type me6-100gb-qsfp28 /configure port 1/1/c1 connector breakout c1-100g /configure port 1/1/c2 connector breakout c1-100g /configure port 1/1/c1 admin-state enable /configure port 1/1/c2 admin-state enable /configure port 1/1/c1/1 admin-state enable /configure port 1/1/c1/1 ethernet mode hybrid /configure port 1/1/c2/1 admin-state enable /configure port 1/1/c2/1 ethernet mode hybrid /configure router interface "system" admin-state enable /configure router interface "system" ipv4 primary address 10.100.1.3 /configure router interface "system" ipv4 primary prefix-length 32 /configure router interface "toR2" admin-state enable /configure router interface "toR2" ipv4 primary address 192.168.23.2 /configure router interface "toR2" ipv4 primary prefix-length 30 /configure router interface "toR2" port 1/1/c1/1:0 /configure router interface "toR5" admin-state enable /configure router interface "toR5" ipv4 primary address 192.168.35.1 /configure router interface "toR5" ipv4 primary prefix-length 30 /configure router interface "toR5" port 1/1/c2/1:0 commit Router R4 (P2) edit-config global /configure system name "R4 (P2)" /configure card 1 card-type iom-1 /configure card 1 mda 1 mda-type me6-100gb-qsfp28 /configure port 1/1/c1 connector breakout c1-100g /configure port 1/1/c3 connector breakout c1-100g /configure port 1/1/c1 admin-state enable /configure port 1/1/c3 admin-state enable /configure port 1/1/c1/1 admin-state enable /configure port 1/1/c1/1 ethernet mode hybrid /configure port 1/1/c3/1 admin-state enable /configure port 1/1/c3/1 ethernet mode hybrid /configure router interface "system" admin-state enable /configure router interface "system" ipv4 primary address 10.100.1.4 /configure router interface "system" ipv4 primary prefix-length 32 /configure router interface "toR2" admin-state enable /configure router interface "toR2" ipv4 primary address 192.168.24.2 /configure router interface "toR2" ipv4 primary prefix-length 30 /configure router interface "toR2" port 1/1/c1/1:0 /configure router interface "toR5" admin-state enable /configure router interface "toR5" ipv4 primary address 192.168.45.1 /configure router interface "toR5" ipv4 primary prefix-length 30 /configure router interface "toR5" port 1/1/c3/1:0 commit Router R5 (PE2) edit-config global /configure system name "R5 (PE2)" /configure card 1 card-type iom-1 /configure card 1 mda 1 mda-type me6-100gb-qsfp28 /configure port 1/1/c1 connector breakout c1-100g /configure port 1/1/c2 connector breakout c1-100g /configure port 1/1/c3 connector breakout c1-100g /configure port 1/1/c1 admin-state enable /configure port 1/1/c2 admin-state enable /configure port 1/1/c3 admin-state enable /configure port 1/1/c1/1 admin-state enable /configure port 1/1/c1/1 ethernet mode hybrid /configure port 1/1/c2/1 admin-state enable /configure port 1/1/c2/1 ethernet mode hybrid /configure port 1/1/c3/1 admin-state enable /configure port 1/1/c3/1 ethernet mode hybrid /configure router interface "system" admin-state enable /configure router interface "system" ipv4 primary address 10.100.1.5 /configure router interface "system" ipv4 primary prefix-length 32 /configure router interface "toR3" admin-state enable /configure router interface "toR3" ipv4 primary address 192.168.35.2 /configure router interface "toR3" ipv4 primary prefix-length 30 /configure router interface "toR3" port 1/1/c2/1:0 /configure router interface "toR4" admin-state enable /configure router interface "toR4" ipv4 primary address 192.168.45.2 /configure router interface "toR4" ipv4 primary prefix-length 30 /configure router interface "toR4" port 1/1/c3/1:0 /configure router interface "toR6" admin-state enable /configure router interface "toR6" ipv4 primary address 192.168.56.1 /configure router interface "toR6" ipv4 primary prefix-length 30 /configure router interface "toR6" port 1/1/c1/1:0 commit Router R6 (CE2) edit-config global /configure system name "R6 (CE2)" /configure card 1 card-type iom-1 /configure card 1 mda 1 mda-type me6-100gb-qsfp28 /configure port 1/1/c1 connector breakout c1-100g /configure port 1/1/c1 admin-state enable /configure port 1/1/c1/1 admin-state enable /configure port 1/1/c1/1 ethernet mode hybrid /configure router interface "system" admin-state enable /configure router interface "system" ipv4 primary address 10.100.1.6 /configure router interface "system" ipv4 primary prefix-length 32 /configure router interface "toR5" admin-state enable /configure router interface "toR5" ipv4 primary address 192.168.56.2 /configure router interface "toR5" ipv4 primary prefix-length 30 /configure router interface "toR5" port 1/1/c1/1:0 commit Verification Step 1: Verify Port Operational Status Verify physical ports are administratively and operationally Up/Up across all routers: ...