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Difficulty: MediumBusiness Continuity and Disaster Recovery

Following a catastrophic data center power outage, a network administrator is executing the business continuity disaster recovery plan to bring enterprise services back online. To prevent system startup failures caused by missing infrastructure dependencies, arrange the following service restoration steps in the correct chronological order from first to last.

  1. 1Restore power and verify layer 2/3 connectivity on core routers and switches.
  2. 2Bring up core network services, including DNS, DHCP, and Active Directory/AAA authentication servers.
  3. 3Power on Storage Area Network (SAN) and Network-Attached Storage (NAS) appliances.
  4. 4Initialize database engines and line-of-business backend application servers.
  5. 5Enable external load balancers and public-facing web application servers.

Answer

The correct sequence of restoration is: 1) Core routers and switches, 2) Core network services (DNS/DHCP/Directory), 3) SAN and NAS storage arrays, 4) Database and backend application servers, and 5) External load balancers and web servers.
Disaster recovery plans enforce a bottom-up restoration hierarchy based on service dependencies: physical network transport switches first, network name resolution and identity services second, shared storage volumes third, backend database/application logic fourth, and external-facing web interfaces fifth.

Step-by-Step Solution

1
Restore physical layer connectivity and core switching/routing infrastructure.
Establishes baseline network transport across subnets and data center racks.
Without functional network switches and routers, devices cannot communicate across subnets.
2
Start core identity and resolution services (DNS, DHCP, Active Directory).
Enables network address assignment, name resolution, and domain authentication.
Storage systems and database servers rely on DNS name resolution and domain authentication during boot.
3
Mount storage arrays (SAN/NAS).
Makes block targets and shared file volumes accessible over iSCSI, Fibre Channel, or NFS/SMB.
Application and database servers will encounter startup errors if target storage volumes are missing.
4
Start database services and internal application backends.
Restores data stores and application business logic.
User-facing services depend on active database connections to fulfill incoming user actions.
5
Enable front-end web servers and route external traffic through load balancers.
Re-opens external client access to enterprise web applications.
Delaying public traffic until all backend dependencies are ready prevents end users from receiving application error pages.

Key Concept

Disaster recovery dependency management and service restoration sequencing
Estimated Time:1m 30s
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Topics

Business Continuity and Disaster Recovery

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