The Solution

No IPs, no network, no business. Each day companies spend a lot of resources and money on network hardware to ensure High Availability, yet often the most overlooked services are DNS and DHCP. Without these basic services, web, email, mobility, CRM, VoIP and other applications will grind to a halt. Depending on the size of the organization, even an hour of downtime can lead to millions of dollars in revenue loss. Today's organizations simply cannot afford that.

BlueCat appliances offer redundancy with failover, automated software updates, error correction utilities, and a number of security provisions to deliver up to five nines (99.999%) availability for DNS and DHCP services. With Proteus and Adonis, mission-critical applications always have access to DNS and DHCP.

XHA

Adonis DNS Crossover High Availability (XHA)

In a DNS XHA configuration, two Adonis appliances are deployed in an active-passive high-availability pair. You can deploy DNS primary servers, secondary servers, or even caching servers in a  XHA configuration.The two appliances share an IP address that DNS clients use for queries.

The appliances connect over the network to keep the passive unit apprised of the ‘health’ of its active partner. If the active appliance should fail, control is transferred to the passive unit and it assumes the active role. When the original active unit is restored, it takes on the passive role.

Many DNS HA systems handle DDNS poorly. The active node receives updates but the passive unit does not, leaving it ill prepared to assume active duty in the event of failover. XHA uses an enslaved primary as the passive node. Updates sent to the active unit are automatically propagated to its passive partner as standard incremental zone transfers. Since both appliances are kept in sync, failover is automatic without manual intervention. Automatic failover ensures customers do not experience a service disruption and resolution latency remains consistent.

'Self Healing' Utility

Adonis DNS appliances feature a Self Healing utility that ensures a valid configuration exists before a passive Adonis appliance joins an XHA cluster. It guarantees that the passive unit is always synchronized with its active partner, even if the passive appliance was unavailable at the time the active unit was configured. The utility also provides repair tools to resolve broken XHA configurations, and ease swap-out of either appliance in the cluster, should replacement be required.

DHCP Failover

A DHCP infrastructure must include a strategy to mitigate all risk to the provisioning of DHCP network services. DHCP Failover provides the necessary redundancy for DHCP services. Unlike XHA which provides redundancy for both DHCP and DNS,  DHCP failover provides protocol-level redundancy exclusively for DHCP.

DHCP Failover divides DHCP pools between two DHCP servers – Adonis appliances in this case – as active-active peers and allows the peers to communicate with each other to maintain a common pool of IP address leases. Each peer assesses the other’s state and if one appliance fails, its peer can readily continue in its place.

The benefits of DHCP Failover include both redundancy and load balancing of IP lease requests. Because both peers maintain common information (number of addresses each has leased, the number  of  free leases each has etc.), failover and load sharing are transparent to DHCP clients.

Failover peers need not be located on the same subnet. This provides great flexibility when deciding where to place DHCP servers. In fact, failover servers are commonly placed on opposite sides of a WAN link, providing distributed services with full geographic fault tolerance.

Whitepapers

Video Library / Webinars

Business Continuity & Disaster Recovery for DNS, DHCP & IPAM

Learn how BlueCat Networks helps you achieve the five nines of network reliability. The most basic network function - namely the ability of devices to receive an IP Address - was not built with failover in mind. Learn how to bring high availability to your network.