Failback
The controlled return of service from a backup or surviving node to the preferred normal topology after a failure is resolved. Failback should account for state synchronization, traffic convergence, and client caching.
Read definitionAlphabetical glossary
F glossary terms
22 definitions beginning with F.
22 terms
Failover
The transfer or continuation of service when a component, site, process, or network path fails. DDI failover can rely on HA clustering, DHCP state sharing, anycast routing, secondary zones, or managed-service distribution.
Read definitionFailover association
A configured relationship between DHCP partners that defines peers, mode, shared address pools, timers, and state. Product implementations may call it a failover relationship, association, or peer relationship.
Read definitionFailover state
The current operational condition of a DHCP failover relationship, such as normal, communications interrupted, partner down, recover, or potential conflict. Exact state names depend on the protocol and product.
Read definitionFast flux
Rapidly changing DNS address records that map a malicious domain to many compromised hosts, often with low TTLs and distributed name servers. It increases resilience for phishing, malware, or proxy infrastructure.
Read definitionFCrDNS
Forward-confirmed reverse DNS, a check in which an address resolves to a PTR name and that name resolves back to the original address. It can be a useful signal but is not proof of identity or authorization.
Read definitionFEC
Forwarding Equivalence Class, an MPLS concept grouping packets that receive the same forwarding treatment. It can appear in network architecture documents but is not a core DDI object.
Read definitionFingerprint
A pattern of observable behavior used to infer device type, software, or activity. DHCP option order, DNS query patterns, EDNS support, and TTL behavior can contribute to a fingerprint.
Read definitionFixed address
A configured mapping that assigns a specific IP address to a matching client, commonly based on MAC address, client identifier, or DUID. In Infoblox terminology, a fixed address is a managed object distinct from a DHCP reservation.
Read definitionFlattening
The process of resolving an alias target within an authoritative platform and returning terminal records to the requester. It is often applied to apex aliases and can obscure target TTL or failure behavior.
Read definitionForward first
A resolver policy that tries configured forwarders first and performs its own iterative resolution if forwarding fails. The fallback can bypass central policy or security controls if not intentionally designed.
Read definitionForward lookup
Resolution from a name to data, most commonly A or AAAA addresses. Forward zones are contrasted with reverse zones that map addresses back to names.
Read definitionForward only
A resolver policy that uses only configured forwarders for selected or all queries and does not fall back to independent recursion. Failure of all forwarders results in query failure.
Read definitionForward zone
A configuration that forwards queries for a selected namespace to designated upstream resolvers. It is a resolver configuration object and is not necessarily an authoritative DNS zone.
Read definitionForward-confirmed reverse DNS
The expanded form of FCrDNS. It validates that a PTR result has a forward address mapping back to the original address.
Read definitionForwarder
A resolver that sends a query to another resolver instead of performing the complete iterative resolution itself. Forwarders can centralize policy, cache, logging, Internet access, or encrypted transport.
Read definitionForwarding resolver
A resolver that relies primarily or entirely on one or more upstream resolvers rather than directly walking the DNS hierarchy. It may still cache responses and enforce local policy.
Read definitionFQDN
Fully Qualified Domain Name, a name that identifies its complete position in the DNS hierarchy. In strict presentation form it includes the trailing root dot, though common usage often omits the visible dot.
Read definitionFragmentation
Splitting an IP packet into smaller fragments because it exceeds a path or link MTU. Fragmented DNS UDP responses are more likely to be lost, filtered, or abused, so modern DNS operations aim to avoid them.
Read definitionFree address
An address that the IPAM system believes is not assigned, reserved, leased, discovered, or otherwise unavailable. "Free" is trustworthy only when discovery and reconciliation are current.
Read definitionFreeze
A product operation that temporarily stops dynamic modifications to a zone so its backing file or data can be edited safely. In BIND, thaw resumes normal dynamic update processing.
Read definitionFull resolver
A resolver capable of performing iterative queries from the DNS root toward the authoritative servers needed to answer a question. It contrasts with a stub resolver that depends on another resolver.
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