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INCIDENT #037 · OSPF

Neighbors are not enough

Easy15 minutesPro lab

The incident

Burlington office. Separate user, guest, monitoring and service edges connect to the campus distribution router. OSPF neighbors are established and the primary service works. Only the secondary service prefix is missing from remote route tables. Investigate the two service networks from R1: 10.205.160.0/24 to 10.205.164.0/24 (TCP/443), and 10.205.161.0/24 to 10.205.165.0/24 (TCP/8443).

Your objective

Restore both authorized service transports and return reachability, including clients and service hosts in both halves of the primary subnet. Keep R4 blocked from both service transports, keep SSH blocked to both service subnets, and preserve monitoring between R1 and R5. Do not change physical topology or addressing. These are network forwarding checks, not application-level transactions.

The network

Network topology5 devices 4 links

Neighbors are not enough — network topologyR1: User access. R2: Distribution. R3: Service gateway. R4: Guest access. R5: Monitoring. R1 connects to R2. R2 connects to R3. R2 connects to R4. R2 connects to R5. Connections show physical links, not service health.R1 ↔ R2 · 10.205.176.0/30R2 ↔ R3 · 10.205.177.0/30R2 ↔ R4 · 10.205.178.0/30R2 ↔ R5 · 10.205.179.0/30R1User accessR1 · User access · Starting deviceR2DistributionR2 · DistributionR3ServicegatewayR3 · Service gatewayR4Guest accessR4 · Guest accessR5MonitoringR5 · Monitoring
Physical links · Service health not shown
Link addressing (4)
  • R1 R210.205.176.0/30
  • R2 R310.205.177.0/30
  • R2 R410.205.178.0/30
  • R2 R510.205.179.0/30
5 devices · Cisco IOS syntax · Simulated network

What you’ll practice

ospf advertisementconnected networksroute lookup

Interview exercises are inspired by common industry competencies. They are not proprietary interview questions.