Glossary – CCNP Enterprise Design ENSLD 300-420 Official Cert Guide: Designing Cisco Enterprise Networks


10GBASE-ER A single-mode fiber for up to 80 kilometers (extended range).

10GBASE-LR A single-mode fiber for up to 10 kilometers (long range).

10GBASE-SR A multimode fiber for up to 400 meters (short range).

20/80 rule A rule which says that 20% of traffic is local, and 80% of traffic is to servers in the data center.

5G An emerging wireless standard based on Release 15 Category NR from the 3GPP standards organization.

6RD (IPv6 Rapid Deployment) A tunnel mechanism that allows a service provider to provide unicast IPv6 service to its customers over its IPv4 network by using encapsulation of IPv6 in IPv4.

ABR (area border router) An OSPF router that is connected to more than one area.

access layer In the hierarchical network model, the layer that provides workgroup and user access to local segments on a network.

administrative distance A rating of the trustworthiness of a routing information source. A lower number is preferred.

ASBR (autonomous system boundary router) An OSPF router that injects external LSAs into the OSPF database.

assurance Contextual insights for quick issue resolution and capacity planning.

automation A simplified deployment option for network devices, along with consistent management of network configurations for both wired and wireless access.

BackboneFast A feature that enables fast convergence in the distribution and core layers when Spanning Tree Protocol changes occur.

BFD (Bidirectional Forwarding Detection) A protocol that captures delay, jitter, and packet loss information.

BGP (Border Gateway Protocol) An interdomain routing protocol that allows BGP speakers residing in different autonomous systems to exchange routing information.

BIDIR-PM (Bidirectional PIM) A variant of PIM-SM that builds bidirectional shared trees connecting multicast sources and receivers. It never builds a shortest path tree, and it can scale well because it does not need a source-specific state.

BPDU Filter A feature that suppresses BPDUs on ports.

BPDU Guard A feature that disables a PortFast-enabled port if a BPDU is received.

BW (bandwidth) The capacity of an interface or a link.

CBWFQ (class-based weighted fair queuing) A scheduling mechanism that defines traffic classes that correspond to match criteria, including ACLs, protocols, and input interfaces.

Cisco DNA Center A Cisco tool that helps with design settings, policy definition, and automated provisioning of network devices along with assurance analytics for both wired and wireless networks.

classification The process of identifying the type of traffic.

congestion management A mechanism to handle traffic overflow using a queuing algorithm.

core layer In the hierarchical network model, the layer that provides fast transport between distribution switches in the enterprise campus. Provides a high-speed switching backbone with high reliability and redundancy.

delay A metric based on how long it takes a packet to reach the destination.

DHCP (Dynamic Host Configuration Protocol) A protocol that dynamically configures devices on a network.

DHCPv6 (Dynamic Host Configuration Protocol version 6) A protocol used for dynamic configuration of devices in an IPv6 network.

dial-in mode A mode in which a network device listens until the receiver dials in and sends the initial SYN packet to start the TCP connection.

dial-out mode A mode in which a network device dials out and sends the initial SYN packet to start the TCP connection to the receiver.

DiffServ A QoS model that separates traffic into multiple classes that can be used to satisfy varying QoS requirements.

distance-vector routing protocol A routing protocol that advertises the entire routing table to its neighbors.

distribution layer In the hierarchical network model, the layer that provides policy-based connectivity and aggregation of access layer devices. It is an isolation point between the access and core layers. Security filtering, aggregation of wiring closets, QoS, and routing between VLANs occur at this layer.

DMVPN (Dynamic Multipoint VPN) A Cisco IOS solution for building IPsec over GRE VPNs in a dynamic and scalable manner.

DNS (Domain Name System) An Internet-based directory system that returns the destination IP address, given a domain name.

DNS64 A Domain Name System (DNS) mechanism that synthesizes AAAA records from A records.

DR (designated router) An OSPF router type in a multiaccess network that collects LSAs for the multiaccess network and forwards them to all non-DR routers; this arrangement reduces the amount of LSA traffic generated.

DSCP (Differentiated Services Code Point) Bits in an IPv4 header that are used to identify traffic that needs priority.

DWDM (dense wavelength-division multiplexing) A WAN technology used to increase the bandwidth capabilities of fiber by using different wavelengths of light called channels over the same fiber strand.

EGP (exterior gateway protocol) A routing protocol type that exchanges routes between administrative domains (for example, BGP).

EIGRP (Enhanced Interior Gateway Routing Protocol) Cisco’s proprietary routing protocol.

enterprise edge module Consists of the demilitarized zone (DMZ) and SP edge.

fabric control plane The part of the network that provides logical mapping and resolution of endpoint IDs to users/devices using Locator/ID Separation Protocol (LISP).

fabric data plane The logical overlay created by Virtual Extensible LAN (VXLAN) packet encapsulation along with a Group Policy Object (GPO).

fabric policy plane The part of a network where network security policy is applied through scalable group tags (SGTs) and group-based policies.

fabric wireless A technology that allows wireless traffic to take advantage of the security benefits of using SGTs with the SD-Access fabric.

FEC (Fast EtherChannel) A technology that bundles 2, 4, or 8 Fast Ethernet links for increased bandwidth.

FHRP (first-hop routing protocol) A protocol that deals with first hop routing. Options are HSRP, VRRP, and GLBP.

FQDN (fully qualified domain name) The complete host domain name of a device.

GEC (Gigabit EtherChannel) A technology that bundles 2, 4, or 8 Gigabit Ethernet links together for increased bandwidth.

GETVPN (Group Encrypted Transport VPN) A technology for creating tunnel-less VPNs over private WANs.

GLBP (Global Load Balancing Protocol) A Cisco-proprietary protocol that attempts to overcome the limitations of existing redundant router protocols by adding basic load balancing functionality. In addition to being able to set priorities on different gateway routers, GLBP allows a weighting parameter to be set.

hop count A metric that counts the number of links between routers the packet must traverse to reach a destination.

HSRP (Hot Standby Routing Protocol) A Cisco-proprietary first-hop routing protocol that provides redundancy by creating a virtual router out of two or more routers.

IANA (Internet Assigned Numbers Authority) The global organization responsible for coordination of the DNS root, IP addressing, and other Internet Protocol resources.

ICMPv6 (Internet Control Message Protocol version 6) A protocol that is an integral part of IPv6 and that performs error reporting and diagnostic functions.

ID (identifier) A number that identifies a host network interface.

IGMP (Internet Group Management Protocol) The protocol used in multicast implementations between end hosts and a local router.

IGP (interior gateway protocol) A routing protocol type that exchanges routes within an administrative domain (for example, OSPF and EIGRP).

IntServ A QoS model that benefits real-time applications by explicitly reserving network resources and giving QoS treatment to user packet flows.

IPsec (IP Security) A security architecture that operates in a host to protect IP traffic. The IETF defined IPsec in RFC 4301. IPsec uses open standards and provides secure communication between peers to ensure data confidentiality, integrity, and authentication through network layer encryption.

IPv4 (Internet Protocol version 4) A 32-bit IP addressing format used in networking.

ISATAP (Intra-Site Automatic Tunnel Addressing Protocol) An IPv6 transition mechanism that involves transmitting IPv6 packets between dual-stack nodes over an IPv4 network.

IS-IS (Intermediate System-to-Intermediate System) A interior gateway routing protocol defined by the OSI with link-state characteristics.

LACP (Link Aggregation Control Protocol) A protocol defined in IEEE 802.3ad that provides a method to control the bundling of several physical ports to form a single logical channel.

link-state routing protocol A routing protocol that uses Dijkstra’s shortest path algorithm to calculate the best path.

LLQ (low-latency queuing) A feature that provides a strict priority queue to delay-sensitive traffic such as voice to be sent before other queues are serviced.

load A metric based on the degree to which an interface link is busy.

Loop Guard A feature that prevents an alternate or root port from being the designated port in the absence of BPDUs.

LSA (link-state advertisement) A message that is used to communicate network information such as router links, interfaces, link states, and costs.

model-driven telemetry A mechanism to stream data from a model-driven telemetry–capable device to a receiver.

MP-BGP (Multiprotocol Border Gateway Protocol) A BGP extension that is used to carry MPLS VPN information between all provider edge (PE) routers within a VPN community.

MPLS (Multiprotocol Label Switching) Layer 3 VPN A technology for the delivery of IP services using an efficient encapsulation mechanism.

MSDP (Multicast Source Discovery Protocol) A protocol that is used to connect multicast domains.

MST (Multiple Spanning Tree) A protocol that is used to reduce the total number of spanning-tree instances that match the physical topology of the network, reducing the CPU load.

MTU (maximum transmission unit) The MTU is the largest size packet or frame that can be sent.

NAT (Network Address Translation) A process that involves converting IP address space into globally unique IP addresses.

NAT64 A Network Address Translation (NAT) transition mechanism that translates between IPv4 and IPv6 protocols.

ND (Neighbor Discovery) IPv6 protocol responsible for gathering various information, including the configuration of local connections, domain name servers, and gateways used to communicate with more distant systems.

NET (Network Entity Title) An address used by IS-IS that consists of the authority and format identifier (AFI), area ID, system ID, and selector (SEL).

NETCONF (Network Configuration Protocol) A network management protocol defined by the IETF in RFC 6241 that provides rich functionality to manage configuration and state data.

NMS (network management system) A system that runs the applications that manage and monitor managed devices.

NSSA (not-so-stubby area) A stub area that contains an ASBR and generates external Type 7 LSAs.

OMP (Overlay Management Protocol) A protocol that runs within the TLS or DTLS control plane tunnels formed by peering between vEdge routers and vSmart controllers.

OOB (out-of-band) management Network management that uses separate infrastructure to connect to managed devices.

OpenConfig A group of network operators working on developing programmable interfaces and tools for managing networks in a vendor-neutral way.

OSPFv2 (Open Shortest Path First version 2) A routing protocol for IPv4 networks.

OSPFv3 (Open Short Path First version 3) A link-state routing protocol that uses Dijkstra’s shortest path first (SPF) algorithm to calculate paths to IPv6 destinations.

overlay A logical network built on top of the underlay in order to create virtualized networks.

PAgP (Port Aggregation Protocol) A Cisco-proprietary protocol used for automated logical aggregation of Ethernet switch ports (EtherChannel).

PAT (Port Address Translation) A process that involves translating many IP addresses into a single IP address.

PBR (policy-based routing) A method of manually modifying the next-hop addresses of packets or of marking packets to receive differential service based on source address.

periodic publication A subscription that is useful for when a data value changes occasionally but the information needs to be sent in a timely manner.

PIM-SM (Protocol Independent Multicast–Sparse Mode) A protocol that uses shared trees and rendezvous points to reach widely dispersed group members with reasonable protocol bandwidth efficiency.

PoE (Power over Ethernet) A technology that provides power to end devices such as IP phones, wireless access points, and video cameras via UTP cabling.

policy An automated configuration to enable group-based security policies and network segmentation.

PortFast A feature that bypasses the listening and learning phases to transition directly to the forwarding state.

RBAC (role-based access control) A policy-neutral access control mechanism defined around roles and privileges. The components of RBAC such as role/permissions, user/role, and role/role relationships make it simple to perform user assignments.

reliability A measure of a given application’s availability to its users.

response time A measure of the time between a client user request and the response from the server host.

RESTCONF An HTTP-based protocol defined in RFC 8040 that provides a programmatic interface for accessing YANG modeled data.

RIPng (Routing Information Protocol next generation) A distance-vector routing protocol for IPv6 networks.

RMON (Remote Monitoring) A standard monitoring specification that enables network monitoring devices and console systems to exchange network monitoring data.

Root Guard A feature that prevents external switches from becoming the root of the Spanning Tree Protocol tree.

scalable group A group defined in the Group ID field of the VXLAN header as part of group-based policy.

SD-Access fabric The physical and logical network infrastructure.

SDN (software-defined networking) A form of networking that abstracts the underlying network infrastructure away from its applications. SDN decouples the forwarding plane from the control and management planes to enable centralization of network intelligence.

SD-WAN A Cisco enterprise-grade software-based WAN architecture overlay that enables digital and cloud transformation for enterprises. It fully integrates routing, security, centralized policy, and orchestration into largescale networks. It is a multi-tenant, cloud-delivered, highly automated, secure, scalable, and application-aware solution with rich analytics.

SNMP (Simple Network Management Protocol) An IP application layer protocol that has become the standard for the exchange of management information between network devices.

SONET/SDH A circuit-based technology that delivers high-speed services over an optical network.

Spanning Tree Protocol A protocol that prevents loops from being formed when switches are interconnected via multiple paths.

SSM (Source-Specific Multicast) A variant of PIM-SM that builds trees, each rooted in just one source. SSM eliminates the rendezvous points and shared trees of sparse mode and only builds a source path tree.

throughput A measure of the data transferred from one host to another in a given amount of time.

ToS (Type of Service) An IP header field that is used to specify QoS parameters.

traffic shaping and policing: Mechanisms that avoid congestion by policing ingress and egress flows.

UDLD (Unidirectional Link Detection) A Cisco protocol that is used on unidirectional links (optical fiber) to prevent traffic blackholing and loops.

underlay A collection of physical switches and routers running a dynamic Layer 3 routing protocol used as the underlying transport for the SD-Access network.

UplinkFast A feature that enables fast uplink failover on an access switch.

vBond A software-based component that performs initial authentication of vEdge devices.

vEdge A routing component of the SD-WAN architecture that delivers WAN, security, and multi-cloud capabilities. These components can be delivered as hardware, software, cloud, or virtual components.

virtual network A separate routing and forwarding instance that provides isolation for host pools or IP subnets.

VLAN (virtual local-area network) A broadcast domain that is isolated within Layer 2 and defined logically. Ports in a LAN switch are assigned to different VLAN numbers.

VLSM (variable-length subnet masking) The process of dividing a network into subnets of various sizes.

vManage A centralized network management system that provides a GUI interface to monitor, configure, and maintain all Cisco SD-WAN devices and links in the underlay and overlay networks.

VPLS (Virtual Private LAN Service) A Cisco VPN technology that allows for the connection of multiple sites into a single Layer 2 domain over a managed IP/MPLS network.

VPWS (Virtual Private Wire Service) A Layer 2 VPN technology commonly referred to as pseudowires.

VRRP (Virtual Router Redundancy Protocol) A standards based first-hop routing protocol that provides redundancy with a virtual router elected as the master.

vSmart The brains of the SD-WAN architecture, which provides routing, enforces policy, and enforces segmentation.

VSS (Virtual Switching System) A Cisco technology that allows certain Cisco switches to bond together as a single virtual switch.

VSS (Virtual Switching System) A Cisco technology that converts two physical switches into one logical switch.

VTP (Virtual Trunking Protocol) A Cisco-proprietary protocol that reduces the administration in a switched network.

window size The upper limit of frames that can be transmitted without a return acknowledgment.

WoL (Wake on LAN) A feature that allows a network administrator to remotely power up sleeping machines.

XML (Extensible Markup Language) A markup language similar to HTML that was designed to store and transport data.

YANG (Yet Another Next Generation) A data modeling language used to describe the data for network configuration protocols.