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Difficulty: HardBusiness Continuity and Disaster Recovery

Following a total power loss and system shutdown across an enterprise primary data center, a network engineer is executing the disaster recovery plan to restore network operations safely and prevent authentication failures or dependency loops. Place the following restoration steps into the correct sequence from first to last.

  1. 1Restore core network switching, routing hardware, and physical inter-rack links.
  2. 2Bring up core IP address assignment (DHCP) and domain name resolution (DNS) infrastructure services.
  3. 3Power on centralized authentication and directory servers (Active Directory, RADIUS, TACACS+).
  4. 4Initialize application host clusters and enterprise database servers.
  5. 5Re-enable perimeter firewalls and external ingress traffic routes.

Answer

The correct sequence for infrastructure restoration is: 1) Core switching and routing hardware, 2) DHCP and DNS infrastructure services, 3) Centralized authentication and directory servers, 4) Application clusters and database servers, and 5) Perimeter firewalls and external ingress routes.
In disaster recovery and network restoration planning, infrastructure must be restored according to operational dependencies: physical switching and routing network fabrics must be active first, followed by baseline network services like DNS/DHCP, then directory and authentication servers, followed by application and database instances, and finally opening perimeter security gateways to external client traffic.

Step-by-Step Solution

1
Restore physical layer devices, core switches, and routers.
Establishes baseline Layer 2 and Layer 3 reachability across internal network segments.
Higher-layer network protocols and servers cannot operate without underlying physical and logical connectivity.
2
Start fundamental network services (DHCP and DNS).
Allows hosts to resolve domain names and receive dynamic IP configurations.
Authentication and application servers depend on DNS host record resolution to communicate across subnets.
3
Initialize identity, authentication, and access control platforms (Active Directory, RADIUS).
Enables domain services, user authentication, and network device access authorization.
Database and application services require domain authentication services to establish secure service accounts and client permissions.
4
Start business application nodes, databases, and middle-tier servers.
Brings business operations platforms back into a functional state.
Applications depend on database availability, user directory verification, and underlying IP infrastructure.
5
Re-open edge security gateways and external routing ingress.
Allows external users and partners to access fully verified internal applications.
Opening perimeter access prematurely exposes half-initialized services to security vulnerabilities and traffic flooding.

Key Concept

Infrastructure Dependency Restoration Sequencing in Business Continuity
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Topics

Business Continuity and Disaster Recovery

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