Category glossary

Networking glossary

22 definitions associated with Networking.

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Browse Networking definitions

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Application delivery controller (ADC)

A load balancer or traffic-management platform that can proxy application traffic and may also perform DNS-based global server load balancing. ADC-generated DNS queries and health checks often appear in DDI telemetry.

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Egress filtering

Network filtering that blocks packets with invalid or unauthorized source addresses from leaving a network. It is a major defense against source-address spoofing used in DNS reflection attacks.

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EUI-48

A 48-bit Extended Unique Identifier, commonly the format used for Ethernet MAC addresses. DHCP reservations and DUID types often derive identity from a link-layer address.

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EUI-64

A 64-bit Extended Unique Identifier format. Modified EUI-64 was historically used to form IPv6 interface identifiers from MAC addresses, though modern systems often use privacy or stable-random identifiers instead.

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Fragmentation

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.

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Host

A network-connected system that originates or terminates traffic. In DNS usage, "host" is informal and should not be assumed to mean that every domain name has an address record.

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Ingress filtering

Filtering traffic entering a network based on whether the source address is plausible and authorized for that path. It helps stop spoofing and protects services from malformed or unexpected traffic.

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Interface ID

An identifier associated with a network interface. In IPv6, the more precise term Interface Identifier refers to the address bits following the subnet prefix; management systems may also use interface ID for an inventory key.

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MAC address

A link-layer hardware address, commonly 48 bits on Ethernet. DHCPv4 often uses it as part of client identity, but it can be changed, duplicated, or hidden behind relays.

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NAC

Network Access Control, a system that evaluates device or user identity and posture before or during network access. NAC platforms often consume DHCP bindings, DNS telemetry, and IPAM context.

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Operational technology (OT)

Industrial, building, medical, or process-control systems that interact with physical operations. OT DDI designs often emphasize deterministic change control, long device lifecycles, isolated networks, and legacy protocols.

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Port

A transport-layer number used by TCP, UDP, SCTP, or DCCP to identify an application endpoint. DNS commonly uses port 53, DHCPv4 uses 67/68, and DHCPv6 uses 546/547.

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RARP

Reverse Address Resolution Protocol, an obsolete method for a host to learn its IPv4 address from its link-layer address. BOOTP and then DHCP replaced it.

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Service IP

An address representing a service rather than a single physical interface, such as a VIP, anycast address, cluster address, or load-balancer frontend.

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Source validation

Verification that a packet's source address is legitimate for the interface, route, binding, or customer from which it arrived. Techniques include ACLs, uRPF, DHCP snooping bindings, SAVI, and provider filtering.

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User Datagram Protocol (UDP)

A connectionless transport protocol that sends independent datagrams without delivery, ordering, or duplicate-suppression guarantees. DNS and DHCP commonly use UDP, while applications add reliability themselves or switch to another transport when required.

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VIP

Virtual IP address, a service address presented by a cluster, load balancer, HA pair, or other abstraction rather than tied permanently to one interface.

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VLAN

Virtual LAN, a Layer 2 broadcast-domain segmentation identified by a VLAN ID on Ethernet networks. A VLAN often maps to one or more IP subnets, but the relationship is not inherently one-to-one.

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VLAN pool

A defined set or range of VLAN IDs available for allocation to domains or encapsulations. In Cisco ACI, VLAN pools are associated with physical or virtual domains and AAEP policy.

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VNI

Virtual Network Identifier, a 24-bit VXLAN segment identifier. A VNI represents a logical overlay segment and can map to a bridge domain or tenant network.

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Well-known port

A transport port in the IANA system range 0 through 1023, generally associated with widely recognized services. DNS port 53 and DHCP server port 67 are examples.

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Zero configuration networking

A set of techniques that allow basic local networking without central configuration, commonly including IPv4 link-local addressing, IPv6 SLAAC, multicast DNS, and DNS Service Discovery.

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