HomeIncident briefing
Back to the library
INCIDENT #178 · SECURITY

Service edge: The new service host fails its network check

Hard25 minutesPro lab

The incident

Internal API clients and an independent observability edge share a transit network with an isolated partner segment. Independent north and south core paths connect the ingress and egress routers. The primary service transport succeeds to .10 but fails to .200 in the same destination subnet. ICMP to both addresses still works. Investigate internal API transport from R1: 10.173.32.0/24 to 10.173.42.0/24 (TCP/8443), and 10.173.33.0/24 to 10.173.43.0/24 (TCP/443).

Your objective

Restore both authorized service transports and return reachability, including clients and service hosts in both halves of the primary subnet. Keep R3 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

Service edge: The new service host fails its network check — network topologyR1: Client edge. R2: Ingress. R3: North core. R4: South core. R5: Egress. R6: Service gateway. R1 connects to R2. R2 connects to R3. R2 connects to R4. R3 connects to R5. R4 connects to R5. R5 connects to R6. Connections show physical links, not service health.R1 ↔ R2 · 10.173.48.0/30R2 ↔ R3 · 10.173.49.0/30R2 ↔ R4 · 10.173.50.0/30R3 ↔ R5 · 10.173.51.0/30R4 ↔ R5 · 10.173.52.0/30R5 ↔ R6 · 10.173.53.0/30R1Client edgeR1 · Client edge · Starting deviceR2IngressR2 · IngressR3North coreR3 · North coreR4South coreR4 · South coreR5EgressR5 · EgressR6ServicegatewayR6 · Service gateway
Physical links · Service health not shown
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.