Cisco SPRI 300-510 key terms

A logical grouping of OSPF interfaces that share a common link-state database; topology detail stays inside the area and is summarized at area borders to limit flooding and SPF scope.

An OSPF router with at least one interface in the backbone area and one in another area. It originates summary LSAs to describe inter-area prefixes in both directions.

An OSPF inter-area prefix advertisement generated by an ABR. It carries a cost from the advertising router and is flooded only within the target area, never across a virtual link as a summary.

An OSPF AS-external advertisement flooded throughout the domain by an ASBR. It carries a metric type (E1 or E2), a forwarding address, and an external route tag used for redistribution control.

An OSPF external advertisement originated inside a not-so-stubby area. The NSSA ABR translates it to a Type 5 LSA for the rest of the domain, optionally preserving the P-bit for forwarding address use.

An OSPF router that injects routes from another protocol or process into the OSPF domain. It originates Type 5 LSAs, or Type 7 LSAs when attached to an NSSA.

The controlled injection of routes learned by one routing protocol into another, with a seed metric, optional route map, and tag applied so that loops and suboptimal paths can be prevented.

The initial metric assigned to redistributed routes because the source protocol's metric is not comparable. If no seed metric is configured, many platforms assign infinity and the routes are not advertised.

A numeric attribute attached to redistributed routes and carried in LSAs or BGP attributes, used at another redistribution point to filter or set preference and thus break mutual redistribution loops.

The two-tier hierarchy of IS-IS: Level 1 routers share a single area and use a Level 1 database, while Level 2 routers form the backbone; a Level 1-2 router attaches the two with the ATT bit.

The Network Entity Title that uniquely identifies an IS-IS router: an NSAP with a system ID of fixed length and an NSEL byte of zero, unique within the routing domain.

The 32-bit metric encoding carried in extended reachability TLVs. It is required for traffic engineering, for metrics above 63, and for differentiated per-level metric values on modern networks.

A flag a router sets in its link-state PDUs to signal that it is not ready to forward transit traffic; other routers then avoid it for transit while still reaching its directly attached prefixes.

The characteristics attached to BGP prefixes, classified as well-known mandatory, well-known discretionary, optional transitive, or optional nontransitive; they drive the best-path decision and route propagation.

The ordered tie-breaking process used to choose one route per prefix, typically: weight, LOCAL_PREF, locally originated, AS_PATH length, origin, MED, eBGP over iBGP, IGP cost to next hop, and lowest router ID.

A well-known discretionary attribute propagated only within an autonomous system. Higher values are preferred and it is the main tool for choosing an exit point for outbound traffic.

An optional nontransitive attribute used to hint to a neighboring AS which entry point is preferred for inbound traffic. Lower values are better and comparison is normally limited to routes from the same neighbor AS.

Repeating the local AS number in the AS_PATH to make a route look longer and therefore less attractive to remote ASes, influencing inbound traffic without changing the actual path.

An iBGP router allowed to reflect routes learned from one client to other clients and nonclients, removing the need for a full iBGP mesh; it uses ORIGINATOR_ID and CLUSTER_LIST to prevent loops.

An identifier carried in the CLUSTER_LIST attribute by a route reflector to detect and discard routing loops when clients are served by redundant reflectors in the same cluster.

A method of dividing one autonomous system into sub-ASes that peer with eBGP-like rules internally while presenting a single AS number to the outside world, reducing the iBGP mesh requirement.

The requirement that the BGP NEXT_HOP be resolvable in the IGP (or via a static or recursive route) before the prefix is installed; otherwise the route stays in the table but is unusable.

A neighbor setting that makes the router advertise its own address as NEXT_HOP for iBGP-learned routes, so that internal peers do not need IGP reachability to an external next hop.

A protocol that binds a label to each IGP prefix and distributes those bindings to LDP peers, building the label-switched paths used for basic MPLS forwarding.

The label information base holds all received label bindings, while the label forwarding information base holds only the selected, installed entries actually used to swap labels and forward packets.

The behavior in which the router one hop before the egress pops the label so the egress receives a plain IP packet, saving it a lookup and label operation.

A traffic-engineered label-switched path signaled with RSVP-TE along an explicitly computed path, reserving bandwidth and using constrained SPF to honor link attributes.

The signaling protocol that establishes and maintains MPLS traffic engineering tunnels, carrying the explicit route object, label request, and bandwidth reservation along the path.

A path computation that runs SPF on the TE topology database while pruning links that fail bandwidth, affinity, or administrative constraints, producing the explicit path for a tunnel.

The range of MPLS labels reserved for global segments, where each SR-capable router is assigned a unique index so that the same label means the same node throughout the domain.

A globally significant segment identifying a router's loopback prefix, formed by adding the node's index to the SRGB start; packets steered with it follow the shortest path to that node.

The ordered stack of segments a packet must traverse, encoded as an MPLS label stack in SR-MPLS or as a segment routing header in SRv6, defining the explicit path.

An IPv6 prefix assigned to a node that aggregates its locally instantiated SRv6 SIDs, making them reachable through normal IPv6 routing and allowing prefix summarization in the IGP.

A multicast routing protocol that builds a shared tree rooted at a rendezvous point and then optionally switches to a shortest-path source tree, using explicit joins and periodic refreshes.

A PIM mode in which receivers join a specific source and group channel directly, building a shortest-path tree without a rendezvous point or shared tree, typically using IGMPv3.

The router that roots the shared tree in PIM-SM, where sources register and receivers join before traffic moves to a source-specific shortest-path tree.

A protocol that lets rendezvous points in different PIM-SM domains exchange information about active sources, enabling inter-domain multicast when a single shared RP is not used.

A label distribution protocol that builds multipoint label-switched paths for multicast in an MPLS network, using a root node and opaque FEC elements instead of per-source trees.

The check that a multicast packet arrived on the interface the unicast routing table uses to reach the source; failure drops the packet and is a common cause of multicast outages.

A high-availability feature that keeps routing protocols running across a switchover by synchronizing state to a standby processor, so no protocol adjacencies are torn down.

The forwarding behavior during a control-plane restart in which the data plane keeps forwarding using existing entries while the routing protocol rebuilds its state with helper neighbors.

A mechanism where a restarting router signals neighbors to hold adjacencies and continue advertising routes for a period, allowing the control plane to recover without a forwarding outage.

A lightweight hello protocol that detects path failures in subsecond time between two routers, independent of the routing protocol, and can trigger faster reconvergence.

An operation where the local system sends echo packets that the remote peer loops back, so failure detection depends on the local timer rather than on the peer's ability to process BFD packets.

Topology-independent loop-free alternate: a Segment Routing fast-reroute method that precomputes a backup path for every possible failure using a post-convergence path and a repair segment list.

A BGP feature that precomputes and installs a backup path for a prefix so that, when the primary path fails, the backup can be promoted without waiting for BGP best-path recalculation.