Industrial campus: The permit rule is present but traffic fails
The incident
Engineering stations reach plant service gateways through the site core and two production aggregation layers. Independent north and south core paths connect the ingress and egress routers. Route checks and ICMP succeed. The primary service transport fails even though an allow rule appears in the service access list. Investigate plant gateway transport from R1: 10.177.224.0/24 to 10.177.234.0/24 (TCP/502), and 10.177.225.0/24 to 10.177.235.0/24 (TCP/4840).
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
Link addressing (6)
- R1 R2
10.177.240.0/30 - R2 R3
10.177.241.0/30 - R2 R4
10.177.242.0/30 - R3 R5
10.177.243.0/30 - R4 R5
10.177.244.0/30 - R5 R6
10.177.245.0/30
What you’ll practice
Interview exercises are inspired by common industry competencies. They are not proprietary interview questions.