BlueCatのDNS用語集

An A record is a DNS record that maps domain names to IPv4 addresses.

An AAAA record is a DNS record that maps domain names to IPv6 addresses.

An ACL is an ordered set of permit and deny rules that controls which sources can reach a system or perform specific actions.

ARP is the network protocol that maps IPv4 addresses to MAC addresses on a local network segment so devices can deliver frames to each other.

Anycast is an addressing and routing method in which multiple servers share one IP address and routers deliver each packet to the nearest one.

An authoritative DNS server holds the original records for a DNS zone and returns definitive answers for names in that zone to resolvers.

BGP is the exterior gateway protocol that autonomous systems use to exchange routing and reachability information, and it determines how traffic crosses the internet.

A bridgehead server is the domain controller in an Active Directory site that sends and receives replication data between that site and other sites.

Broadcast routing delivers a packet to every node in a network or network segment, whether or not each node needs the data.

A caching DNS server resolves DNS queries for clients and stores the answers for a limited time so repeat lookups are answered faster.

CIDR is an IP addressing and routing method that uses variable-length prefixes instead of fixed address classes, allowing flexible allocation and smaller routing tables.

Classful networks were the original IPv4 addressing scheme, which split the address space into fixed classes A, B, C, D and E based on the leading bits of an address.

A CNAME record is a DNS record type that makes one domain name an alias of another, so resolvers follow it to the canonical name.

Conditional DNS forwarding sends queries for named domains to specific DNS servers while all other queries follow the default resolution path.

DDI (DNS, DHCP, and IPAM) integrates DNS, DHCP, and IPAM into one management solution.

DDI architecture is the design that integrates DNS, DHCP, and IP address management so network addressing and name resolution are managed from one coordinated system.

DDI orchestration coordinates DNS, DHCP and IPAM changes through automated workflows so address, name and lease data stay consistent across systems.

A default gateway is the router address a host uses to send traffic to any destination outside its own subnet.

DHCP (Dynamic Host Configuration Protocol) is the standard mechanism to dynamically assign IP addresses within a network.

A DHCP lease is the time-limited right a client has to use an IP address and configuration that a DHCP server assigned to it.

A DHCP relay agent forwards DHCP messages between clients and servers on different subnets, so one central server can serve many network segments.

A DHCP reservation binds a specific IP address to a device's identifier so the DHCP server always offers that device the same address.

A DHCP scope is the pool of IP addresses and configuration options a DHCP server may lease to clients on one subnet.

DHCP snooping is a switch security feature that filters DHCP messages to block rogue DHCP servers and record which clients hold which leases.

DHCPACK is the DHCP message a server sends to confirm a lease and deliver the final configuration parameters to a client.

DHCPDISCOVER is the broadcast message a DHCP client sends first to locate available DHCP servers and begin obtaining an IP address lease.

A DHCP message a server sends to tell a client that its requested address or configuration is invalid, so the client must restart the process.

DHCPOFFER is the DHCP message a server sends to a client to propose an IP address and configuration parameters after a DHCPDISCOVER.

DHCPREQUEST is the DHCP message a client sends to accept an offered lease, renew an existing lease, or confirm a previously used address.

A DMZ is a separate network segment that hosts external-facing services so that internet traffic does not reach the internal network directly.

DNS delegation hands authority for a subdomain to separate name servers, which lets different teams or organizations manage their own part of the namespace.

DNS filtering allows or blocks domain name lookups according to policy and threat data, preventing devices from reaching unwanted or malicious destinations.

A DNS glue record is an address record held in a parent zone that lets resolvers reach name servers located inside the delegated domain.

The DNS namespace is the hierarchical tree of domain names, from the root down through top-level and lower-level domains, that DNS uses to name and locate resources.

DoH encrypts DNS queries and responses by sending them over HTTPS, which hides resolver traffic from on-path observers and blends it with web traffic.

DNS over TLS encrypts DNS queries and responses between clients and resolvers by wrapping them in a TLS session on a dedicated port.

A DNS query is a request a DNS client sends to a DNS server to obtain information, such as an IP address, for a domain name.

DNS rebinding is an attack that changes a DNS answer after a page loads so a victim's browser reaches internal network resources.

A DNS Root Server is a name server that answers requests for records in the root zone and directs other requests to authoritative name servers for appropriate top-level domains.

A DNS server stores DNS records and responds to DNS queries from devices, resolving domain names to IP addresses.

DNS spoofing is an attack that injects false DNS data so users or systems resolve a legitimate name to an attacker-chosen IP address.

A DNS stub resolver is the client-side software that sends DNS queries to a recursive resolver and returns the answers to applications.

A DNS zone is the portion of the domain name space that one administrator manages, stored as a set of resource records on authoritative servers.

The Domain Name System (DNS) is a hierarchical naming system that resolves domain names to IP addresses, enabling communication across network devices.

The DORA process is the four-message DHCP exchange of discover, offer, request, and acknowledge that lets a client obtain an IP address lease from a server.

Dynamic DNS updates DNS records automatically when a host's IP address changes, so its domain name keeps resolving to the correct address.

A dynamic IP address is an address a server assigns to a device for a limited time, so the address can change between leases.

EIGRP is a routing protocol that lets routers inside one network share routes and choose paths using the Diffusing Update Algorithm.

A forwarding DNS server passes queries it cannot answer locally to another DNS server, which resolves them and returns the result for caching.

An FQDN is a complete domain name that identifies one host or service by listing every label from the host up to the DNS root.

Geocast delivers a message to every node located inside a defined geographic region, using location rather than host identity or group membership as the address.

A GUID is a 128-bit value generated to be unique across systems, used to identify objects, records and devices without a central registry.

HTTP is the application-layer request and response protocol that web browsers, APIs and servers use to exchange web resources such as pages, images and data.

An IP address is a numeric label that identifies a network interface and its location so devices can send and receive packets on an IP network.

An IP host is any device that sends or receives IP packets as an endpoint, with one or more IP addresses but without forwarding traffic for others.

An IP address conflict happens when two devices on the same network use the same IP address, causing intermittent or total loss of connectivity.

IP address discovery is the process of scanning a network to find which IP addresses are in use, so address records match reality.

IP address exhaustion is the condition in which no unassigned addresses remain in a pool, subnet or address registry, so new devices cannot connect.

IP address lifecycle management governs each IP address from planning and allocation through monitoring, reclamation and retirement, so records match what is actually in use.

IP address management (IPAM) is a method for planning, tracking, and managing IP address space on a network.

Internet Protocol version 4 (IPv4) is the fourth version of Internet Protocol using 32-bit addresses to route most current internet traffic; its global supply is exhausted.

Internet Protocol version 6 (IPv6) is the most recent version of Internet Protocol, using 128-bit address space with approximately 340 undecillion available addresses.

The IPv6 loopback address, ::1, lets a host send packets to itself so local software can communicate and be tested without using a physical network.

IPv6 prefix lifetime sets how long a prefix stays preferred and valid for address configuration, controlling when hosts stop using addresses derived from it.

An iterative query is a DNS request in which the queried server returns its best answer or a referral to another server, without querying others.

LDAP is an open application protocol that lets clients search, read and modify entries in a directory service, most often for authentication and identity lookups.

A LAN is a network that connects devices within a limited area, such as an office, building or campus, so they can communicate and share resources.

Multicast is a one-to-many delivery method in which a single packet stream reaches only the hosts that have joined a specific group address.

An MX record is a DNS record that provides the domain names of mail servers that receive emails on behalf of a domain.

A nameserver is a server that answers DNS queries by returning records for the names it is authoritative for or by resolving names on behalf of clients.

NAT rewrites IP addresses, and often port numbers, in packet headers as traffic crosses a router or firewall, letting private networks share public addresses.

A network source of truth is the authoritative record of network devices, addresses, and intended configuration that people and automation systems consult and update.

A non-recursive query asks a DNS server for the best answer it already has, such as cached data or a referral, without the server querying others.

NSD is an open-source authoritative-only DNS name server from NLnet Labs, designed for simplicity, security and reliable zone serving.

NTP synchronizes clocks across networked devices over variable-latency packet networks, giving logs, certificates and authentication a consistent time reference.

OSPF is a link state interior gateway protocol that lets routers inside one autonomous system share topology data and compute shortest paths for IP traffic.

The OSI model is a conceptual model that characterizes and standardizes communication functions of telecommunications or computing systems.

Overlapping IP address space is a condition where separate networks use identical or intersecting IP address ranges, which makes addresses ambiguous when the networks are connected.

Private DNS resolves names for internal resources inside a private network, so internal records and queries stay out of the public DNS.

A PTR record is a DNS record that resolves IPv4 or IPv6 addresses to domain names.

A recursive DNS server resolves domain names on behalf of clients by querying other DNS servers and returning the final answer, caching results.

A recursive query is a DNS request in which the client asks a server to return a final answer or an error, resolving the name on its behalf.

RADIUS is a client/server protocol that centralizes authentication, authorization, and accounting for users and devices connecting to network access points.

A Response Policy Zone is a DNS zone that holds policy rules a recursive resolver uses to block, redirect, or allow answers for chosen domains.

A reverse DNS lookup queries DNS with an IP address to find the domain name mapped to it, using PTR records in special reverse zones.

RFC 1918 networks are the IPv4 address blocks reserved for private use, which organizations can reuse internally and which are not routed on the public internet.

A rogue DNS server is an unauthorized resolver that answers queries with false records, redirecting users to malicious or unintended destinations without their knowledge.

RIP is a distance-vector routing protocol that uses hop count as its metric to choose paths between networks in small environments.

SNMP is an application-layer protocol that lets management systems poll network devices for status data, receive event alerts, and change device settings.

SOAP is an XML-based messaging protocol that lets applications exchange structured data over networks, most often carried over HTTP, in web service environments.

An SNMP module is a defined set of management objects, or the agent software that serves them, that lets a monitoring system query and manage a device.

An SOA record is a DNS record type that provides important details about a DNS zone and is required for every DNS zone.

Split-horizon DNS answers the same domain name query differently depending on where the query comes from, typically separating internal and external views.

SSL is a deprecated cryptographic protocol that encrypts and authenticates traffic between a client and a server, replaced in practice by TLS.

A static IP address is an address manually assigned to a device that stays fixed until an administrator changes it, unlike a dynamically leased address.

A subnet mask is a 32-bit value used with an IPv4 address to separate the network portion from the host portion.

TCP is a connection-oriented transport protocol that delivers an ordered, error-checked byte stream between applications on hosts communicating over an IP network.

DNS TTL is a per-record value, in seconds, that tells resolvers how long they may cache an answer before querying again.

TSIG authenticates DNS messages between two servers or a client and a server using a shared secret key and a keyed hash in each message.

TLS is a cryptographic protocol that encrypts and authenticates data exchanged between two applications, protecting traffic such as web, email and DNS from eavesdropping and tampering.

A TXT record is a DNS record that provides descriptive information in text format.

Unicast is one-to-one network communication in which a packet travels from a single sender to a single receiver identified by a unique address.

UDP is a connectionless transport protocol that sends independent datagrams without a handshake, which makes it fast and the default transport for most DNS and DHCP traffic.

A virtual IP address is an IP address not tied to a single physical network interface, used for failover, load balancing, and address translation.