3.4 Business Continuity, Disaster Recovery (Hot/Warm/Cold) & High Availability
Surveys RTO vs. RPO disaster metrics, MTBF/MTTR reliability equations, disaster recovery facility classifications, and First Hop Redundancy Protocols.
🎯 Key CompTIA Network+ Exam Takeaways
- RTO is the targeted duration to restore operations; RPO defines the maximum tolerable transactional data loss.
- Hot Sites provide real-time mirrored data and instantaneous failover; Warm Sites have hardware but need data restoration; Cold Sites provide space only.
- VRRP (open standard) and HSRP (Cisco) provide default gateway redundancy via virtual IP and virtual MAC addresses.
Business continuity planning ensures enterprise resilience against catastrophic failures. The Recovery Time Objective (RTO) dictates how quickly systems must resume operations, while the Recovery Point Objective (RPO) sets the maximum acceptable data loss.
Disaster recovery facilities range in readiness: Hot Sites maintain operational mirrored hardware and live data replication for near-zero RTO; Warm Sites have pre-installed hardware requiring backup restoration; Cold Sites provide basic physical space and power.
At the campus edge, First Hop Redundancy Protocols (FHRP) like VRRP share a virtual IP and MAC address across multiple physical routers, ensuring that default gateway traffic fails over seamlessly if the active master router fails.
⚠️ Common Pearson VUE Exam Traps
- Inverting RTO and RPO: RTO measures downtime recovery hours; RPO measures lost transaction minutes/hours.
- Selecting HSRP when an open-standard, multivendor First Hop Redundancy Protocol is required (VRRP is the open standard).
Knowledge Checkpoint
A network engineer is implementing default gateway redundancy across two multivendor core switches. The solution must use an open standard protocol that presents a single virtual IP and virtual MAC address to local clients, electing one active Master router while the other remains as a Backup. Which protocol should be selected?