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INCIDENT #236 · SECURITY

Remote access: The permit rule is present but traffic fails

Hard25 minutesPro lab

The incident

Managed remote clients reach access-service gateways over an enterprise transit chain; unmanaged devices use a separate branch. A metro ring feeds a separate aggregation router and service gateway rather than attaching the service directly to the ring. Route checks and ICMP succeed. The primary service transport fails even though an allow rule appears in the service access list. Investigate access gateway transport from R1: 10.180.96.0/24 to 10.180.106.0/24 (TCP/443), and 10.180.97.0/24 to 10.180.107.0/24 (UDP/1194).

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

Remote access: The permit rule is present but traffic fails — 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 · 10.180.112.0/30R2 ↔ R3 · 10.180.113.0/30R3 ↔ R4 · 10.180.114.0/30R4 ↔ R1 · 10.180.115.0/30R4 ↔ R5 · 10.180.116.0/30R5 ↔ R6 · 10.180.117.0/30R1Client metroR1 · Client metro · Starting deviceR2South metroR2 · South metroR3SoutheastmetroR3 · Southeast metroR4Service metroR4 · Service metroR5ServiceaggregationR5 · Service aggregationR6ServicegatewayR6 · Service gateway
Physical links · Service health not shown
6 devices · Cisco IOS syntax · Simulated network

What you’ll practice

acl orderfirst matchleast privilege

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