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INCIDENT #048 · SECURITY

The overly broad deny

Hard25 minutesPro lab

The incident

Orlando service network. A metro ring feeds a separate aggregation router and service gateway rather than attaching the service directly to the ring. The primary service transport succeeds to .10 but fails to .200 in the same destination subnet. ICMP to both addresses still works. Investigate the two service networks from R1: 10.207.0.0/24 to 10.207.10.0/24 (TCP/443), and 10.207.1.0/24 to 10.207.11.0/24 (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 R3. Do not change physical topology or addressing. These are network forwarding checks, not application-level transactions.

The network

Network topology6 devices 6 links

The overly broad deny — network topologyR1: Client metro. R2: South metro. R3: Southeast metro. R4: Service metro. R5: Service aggregation. R6: Service gateway. R1 connects to R2. R2 connects to R3. R3 connects to R4. R4 connects to R1. R4 connects to R5. R5 connects to R6. Connections show physical links, not service health.R1 ↔ R2 · 10.207.16.0/30R2 ↔ R3 · 10.207.17.0/30R3 ↔ R4 · 10.207.18.0/30R4 ↔ R1 · 10.207.19.0/30R4 ↔ R5 · 10.207.20.0/30R5 ↔ R6 · 10.207.21.0/30R1Client metroR1 · Client metro · Starting deviceR2South metroR2 · South metroR3SoutheastmetroR3 · Southeast metroR4Service metroR4 · Service metroR5ServiceaggregationR5 · Service aggregationR6ServicegatewayR6 · Service gateway
Physical links · Service health not shown
Link addressing (6)
  • R1 R210.207.16.0/30
  • R2 R310.207.17.0/30
  • R3 R410.207.18.0/30
  • R4 R110.207.19.0/30
  • R4 R510.207.20.0/30
  • R5 R610.207.21.0/30
6 devices · Cisco IOS syntax · Simulated network

What you’ll practice

acl wildcardsdestination matchingtransport testing

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