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INCIDENT #023 · ROUTING

Requests without replies

Hard25 minutesPro lab

The incident

San Diego branch. Five metro routers provide two directions around the region before the service handoff. Requests reach both service networks, but the second client subnet cannot receive replies. The first client subnet still works. Investigate the two service networks from R1: 10.203.224.0/24 to 10.203.234.0/24 (TCP/443), and 10.203.225.0/24 to 10.203.235.0/24 (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 R2 blocked from both service transports, keep SSH blocked to both service subnets, and preserve monitoring between R1 and R4. Do not change physical topology or addressing. These are network forwarding checks, not application-level transactions.

The network

Network topology6 devices 6 links

Requests without replies — network topologyR1: Client metro. R2: North metro. R3: Northeast metro. R4: South metro. R5: Service metro. R6: Service gateway. R1 connects to R2. R2 connects to R3. R3 connects to R5. R5 connects to R4. R4 connects to R1. R5 connects to R6. Connections show physical links, not service health.R1 ↔ R2 · 10.203.240.0/30R2 ↔ R3 · 10.203.241.0/30R3 ↔ R5 · 10.203.242.0/30R5 ↔ R4 · 10.203.243.0/30R4 ↔ R1 · 10.203.244.0/30R5 ↔ R6 · 10.203.245.0/30R1Client metroR1 · Client metro · Starting deviceR2North metroR2 · North metroR3NortheastmetroR3 · Northeast metroR4South metroR4 · South metroR5Service metroR5 · Service metroR6ServicegatewayR6 · Service gateway
Physical links · Service health not shown
Link addressing (6)
  • R1 R210.203.240.0/30
  • R2 R310.203.241.0/30
  • R3 R510.203.242.0/30
  • R5 R410.203.243.0/30
  • R4 R110.203.244.0/30
  • R5 R610.203.245.0/30
6 devices · Cisco IOS syntax · Simulated network

What you’ll practice

return pathstatic routingbidirectional verification

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