Infoblox DDI Professional NIOS-DDI-Expert Question # 5 Topic 1 Discussion

Comprehensive and Detailed In-Depth Explanation:DHCP Failover in NIOS ensures redundancy between two peers (primary and secondary). When one peer loses power, the state shifts toCOMMUNICATIONS-INTERRUPTED, meaning the remaining peer continues serving DHCP but with limited capacity for new leases. Let’s analyze:

Failover Mechanics:In NORMAL state, peers split the lease pool (e.g., 50/50 or custom split). In COMMUNICATIONS-INTERRUPTED, the surviving peer:

Renews leases for existing clients (using its synced database).

Assigns new leases from its portion of the pool, with reduced capacity (e.g., MCLT—Maximum Client Lead Time—limits new lease duration).

Scenario:Power is out for 1 hour, and new devices are joining. The remaining peer can handle renewals and has some new lease capacity (depending on pool size and MCLT, typically 1 hour by default).

Options:

A:Contacting support and forcing PARTNER-DOWN gives the surviving peer full pool access, but it’s unnecessary for a 1-hour outage with "a few" new clients. Overkill.

B:Increasing lease time (e.g., to 4 hours) prevents lease expiration but doesn’t address new client capacity and requires manual reversion. Unneeded complexity.

C:Reconfiguring relays to point only to the surviving peer is redundant—it’s already receiving requests—and risks misconfiguration. Incorrect.

D:Doing nothing leverages the failover design: existing clients renew seamlessly, and the remaining peer services new clients within its capacity. Correct for this short-term, low-impact scenario.

Practical Example:In an INE lab, you’d monitor the surviving peer’s lease usage (via Grid Manager > DHCP > Leases) and confirm it handles the load, a key troubleshooting skill.References:Infoblox NIOS Administrator Guide – DHCP Failover; INE Course Content: NIOS DDI DHCP Troubleshooting.