OSPF Part 1: Topology Setup and Interface Addressing

Fri, 04 Sep 2026 00:00:00 +0000

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:

OSPF Part 2: Single-Area OSPFv2 (Area 0) Configuration

Fri, 11 Sep 2026 00:00:00 +0000

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.

Routing on Dennis Mwangi

OSPF Part 1: Topology Setup and Interface Addressing

Containerlab Topology File (topology.clab.yml)

Addressing Plan

System (Loopback) Interfaces

Physical Interfaces

Router R1

Router R2

Router R3

Router R4

Router R5

Router R6

Configuration

Router R1 (CE1)

Router R2 (PE1)

Router R3 (P1)

Router R4 (P2)

Router R5 (PE2)

Router R6 (CE2)

Verification

Step 1: Verify Port Operational Status

OSPF Part 2: Single-Area OSPFv2 (Area 0) Configuration

Configuration

Containerlab Topology File (`topology.clab.yml`)