Industrial campus: The port is open for the wrong traffic
The incident
Engineering stations reach plant service gateways through the site core and two production aggregation layers. A partner branch shares the aggregation router but not the service handoff. The primary service port appears in the access list, but its required transport is blocked. Routing and the secondary service are working. Investigate plant gateway transport from R1: 10.178.64.0/24 to 10.178.70.0/24 (TCP/502), and 10.178.65.0/24 to 10.178.71.0/24 (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 R5 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
Link addressing (4)
- R1 R2
10.178.80.0/30 - R2 R3
10.178.81.0/30 - R3 R4
10.178.82.0/30 - R2 R5
10.178.83.0/30
What you’ll practice
Interview exercises are inspired by common industry competencies. They are not proprietary interview questions.