Juniper JNCIS-SP: key terms

Flashcards for this exam Juniper JNCIS-SP guide Class dates

• Address FamilyA BGP (or other protocol) configuration context identifying a type of network layer information, such as IPv4 unicast or L2VPN EVPN.Advanced
• Adj-RIB-InThe conceptual BGP table holding unprocessed routes received from a specific peer before inbound policy.Advanced
• Adjacency SIDA local segment that forces a packet across a specific IGP adjacency (link), regardless of shortest path.Advanced
• Allowas-InA BGP option permitting a router to accept routes containing its own ASN in the AS_PATH.Advanced
• AS-OverrideA PE-side BGP option that replaces the customer's ASN in the AS_PATH with the provider's ASN, letting sites with the same ASN learn each other's routes.Advanced
• AS_PATH AttributeA well-known mandatory BGP attribute listing the ASNs a route has traversed; used for loop prevention and path length comparison.Intermediate
• Attached BitA flag set in an L1/L2 router's Level 1 LSP signalling it has Level 2 connectivity, prompting L1 routers to install a default route.Advanced
• BGP Add-PathA BGP capability that allows advertising multiple paths for the same prefix to a peer.Advanced
• BGP Best Path SelectionBGP's ordered decision process for choosing one best path per prefix.Intermediate
• BGP CommunityAn optional transitive 32-bit BGP attribute (often written AS:value) used to tag routes for policy decisions.Intermediate
• BGP ConfederationSplitting one AS into multiple internal sub-ASes that run eBGP-like sessions among themselves, reducing iBGP mesh size.Advanced
• BGP FlowspecA BGP address family (RFC 8955) that distributes traffic filtering rules matching on packet fields, with actions such as drop or rate-limit.Advanced
• BGP Full MeshThe requirement that every iBGP speaker peer with every other iBGP speaker unless route reflectors or confederations are used.Intermediate
• BGP Link-State (BGP-LS)A BGP address family that exports IGP topology and TE information to controllers such as PCEs.Advanced
• BGP Neighbor StatesThe BGP finite state machine: Idle, Connect, Active, OpenSent, OpenConfirm and Established.Intermediate
• BGP Path AttributesProperties attached to BGP routes, categorized as well-known mandatory, well-known discretionary, optional transitive and optional non-transitive.Intermediate
• BGP Prefix Independent Convergence (BGP PIC)A Cisco feature that precomputes backup BGP paths in the FIB so failover time does not depend on the number of prefixes.Advanced
• BGP Route Reflector (RR)An iBGP router allowed to re-advertise iBGP-learned routes to its clients, removing the full-mesh requirement.Intermediate
• Bidirectional Forwarding Detection (BFD)A lightweight hello protocol that detects forwarding path failures in milliseconds and notifies routing protocols.Intermediate
• Border Gateway Protocol (BGP)The path-vector EGP (BGP-4) that exchanges reachability between autonomous systems and is the routing protocol of the Internet.Foundational
• Cluster ListAn optional non-transitive BGP attribute listing the cluster IDs of route reflectors a route has passed through.Advanced
• Complete Sequence Number PDU (CSNP)An IS-IS PDU listing all LSPs in a router's database, used to synchronize databases.Advanced
• Constrained Shortest Path First (CSPF)A modified SPF that prunes links not meeting constraints (bandwidth, affinity, SRLG) before computing a path.Advanced
• Designated Forwarder (DF)The single EVPN PE on a multihomed Ethernet segment responsible for forwarding BUM traffic toward the segment for a given VLAN.Advanced
• Designated Intermediate System (DIS)The IS-IS router elected on a broadcast segment to create the pseudonode and send periodic CSNPs.Advanced
• Ethernet VPN (EVPN)A BGP-based control plane (RFC 7432) for Layer 2 and Layer 3 VPNs that advertises MAC and IP reachability with multihoming support.Advanced
• EVPN Route TypesEVPN NLRI types: 1 Ethernet A-D, 2 MAC/IP Advertisement, 3 Inclusive Multicast Ethernet Tag, 4 Ethernet Segment and 5 IP Prefix.Advanced
• EVPN-VPWSPoint-to-point Ethernet service signalled with BGP EVPN (RFC 8214) instead of LDP, supporting all-active multihoming.Advanced
• Extended CommunityA 64-bit BGP community with type and value fields, used for route targets, site of origin, EVPN and other functions.Advanced
• Fast Reroute (FRR)Precomputed local protection that switches traffic onto a backup path within about 50 ms of a failure.Advanced
• Filter-Based Forwarding (FBF)Junos policy routing that uses a firewall filter to direct matching traffic to a specific routing instance.Advanced
• Firewall FilterA Junos stateless packet filter, like an ACL, whose terms match packets (from) and apply actions such as accept, discard, count or policer.Intermediate
• Flexible Algorithm (Flex-Algo)An IGP extension that lets operators define additional SPF algorithms (128-255) with custom metrics and constraints, each with its own prefix SIDs.Advanced
• Graceful RestartA mechanism letting neighbors keep forwarding through a restarting router's control plane using preserved forwarding state.Advanced
• IEEE 802.1ad (Q-in-Q)A standard for stacking two VLAN tags (S-tag and C-tag) so providers can carry customer VLANs transparently.Advanced
• Intermediate System to Intermediate System (IS-IS)A link-state IGP originally for OSI CLNS that runs directly over Layer 2 and is widely used in service provider cores.Intermediate
• Internal BGP (iBGP)A BGP session between routers in the same autonomous system.Intermediate
• IS-IS Level 1Intra-area IS-IS routing; L1 routers know only their own area and use the closest L1/L2 router for other destinations.Intermediate
• IS-IS Level 1/2 RouterAn IS-IS router participating in both levels, holding separate L1 and L2 databases, similar to an OSPF ABR.Intermediate
• IS-IS Level 2Inter-area (backbone) IS-IS routing between L2 and L1/L2 routers, which may be in different areas.Intermediate
• IS-IS Route LeakingAdvertising selected Level 2 prefixes into Level 1 so L1 routers choose optimal exits instead of the nearest default.Advanced
• IS-IS Wide MetricsIS-IS extended 24-bit interface and 32-bit path metrics carried in TLVs 22 and 135, replacing the 6-bit narrow metric.Advanced
• Junos Active Route SelectionThe Junos process of choosing one active route per prefix: lowest preference, then protocol-specific tie-breakers.Intermediate
• Junos Class of ServiceJuniper's QoS framework using forwarding classes, loss priorities, behavior aggregate classifiers, schedulers and rewrite rules.Advanced
• Junos OSJuniper Networks' network operating system, built on a FreeBSD-derived kernel (or Linux in Junos OS Evolved) with a single code train across platforms.Foundational
• Junos Routing PolicyJunos import/export policy-statements whose terms use from (match) and then (action) clauses to control routes in and out of routing tables.Intermediate
• Junos Routing TablesDefault Junos tables such as inet.0 (IPv4 unicast), inet.3 (MPLS next hops), inet6.0 (IPv6), mpls.0 (labels) and bgp.l3vpn.0 (VPN routes).Advanced
• Label Distribution Protocol (LDP)A protocol that distributes label bindings for IGP prefixes between MPLS neighbors.Intermediate
• Label StackThe ordered set of MPLS labels on a packet; routers act only on the top label.Intermediate
• Label Switch Router (LSR)Any router that forwards MPLS packets based on labels; core LSRs are called P routers.Intermediate
• Label Switched Path (LSP)The unidirectional path a labeled packet follows from ingress to egress LER through an MPLS network.Intermediate
• LDP-IGP SynchronizationA feature that keeps the IGP from using a link until LDP is operational on it, preventing traffic blackholing.Advanced
• Link-State PDU (LSP)The IS-IS packet that carries a router's link-state information, analogous to an OSPF LSA.Intermediate
• Local Preference (LOCAL_PREF)A well-known discretionary BGP attribute shared among iBGP peers; the highest value is preferred for outbound traffic from the AS.Intermediate
• Loop-Free Alternate (LFA)A precomputed backup next hop that is guaranteed loop-free, enabling sub-50 ms IGP fast reroute.Advanced
• Maximum-PrefixA BGP neighbor limit on the number of prefixes accepted, protecting against route leaks and table overflows.Advanced
• MPLS LabelA 32-bit shim header containing a 20-bit label value, 3-bit Traffic Class (EXP), 1-bit bottom-of-stack flag and 8-bit TTL.Intermediate
• MPLS Layer 3 VPN (L3VPN)A provider service (RFC 4364) that carries customer IP routes in separate VRFs across an MPLS core using MP-BGP.Advanced
• MPLS Traffic Class (TC)The 3-bit field in an MPLS label (formerly EXP) used to carry QoS markings across the core.Advanced
• MPLS Traffic Engineering (MPLS TE)Steering traffic along explicit, constraint-based paths using RSVP-TE tunnels to use network capacity efficiently.Advanced
• Multi-Exit Discriminator (MED)An optional non-transitive BGP attribute that suggests to a neighboring AS which entry point to use; lower is preferred.Intermediate
• Multiprotocol BGP (MP-BGP)Extensions to BGP (RFC 4760) that carry routing information for multiple address families such as IPv6, VPNv4, EVPN and multicast.Advanced
• Multiprotocol Label Switching (MPLS)A forwarding technology that switches packets using short labels instead of IP lookups, enabling VPNs, traffic engineering and fast reroute.Intermediate
• Network Entity TitleThe IS-IS router address in NSAP format, containing the area ID, system ID and NSEL of 00.Intermediate
• Next-Hop-SelfA BGP neighbor option that rewrites the NEXT_HOP to the router's own address when advertising to iBGP peers.Intermediate
• Nonstop Routing (NSR)A high-availability feature where the standby route processor maintains full routing protocol state so neighbors never notice a switchover.Advanced
• Overload BitAn IS-IS LSP flag telling other routers not to use this router for transit traffic.Advanced
• Partial Sequence Number PDU (PSNP)An IS-IS PDU used to acknowledge received LSPs on point-to-point links or request missing LSPs on broadcast links.Advanced
• Path Computation Element (PCE)A controller or router that computes paths for headends, communicating via PCEP.Advanced
• Path Computation Element Communication Protocol (PCEP)The TCP-based protocol (port 4189) between a PCE and path computation clients for path requests, updates and delegation.Advanced
• PE-CE RoutingThe routing protocol between a provider PE (in a VRF) and a customer CE: static, eBGP, OSPF, EIGRP, IS-IS or RIP.Advanced
• Penultimate Hop Popping (PHP)The MPLS behavior where the next-to-last router removes the top label so the egress router does only one lookup.Advanced
• Prefix SIDA global segment associated with an IGP prefix that steers traffic along the ECMP-aware shortest path to that prefix.Advanced
• Provider Edge Router (PE)A service provider router that connects to customer edge devices and holds customer VRFs in MPLS VPNs.Intermediate
• PseudonodeA virtual node representing a broadcast segment in a link-state topology, created by the IS-IS DIS or OSPF DR.Advanced
• Pseudowire (PW)An emulated point-to-point Layer 2 circuit across an MPLS or IP network, carrying Ethernet, Frame Relay or ATM frames.Advanced
• Remote-Triggered Black Hole (RTBH)A DDoS mitigation technique where a BGP-signaled route sends attack traffic to a discard (Null0) next hop at the network edge.Advanced
• Resource Public Key Infrastructure (RPKI)A cryptographic system that lets networks validate that an AS is authorized to originate a prefix (route origin validation).Advanced
• Resource Reservation Protocol (RSVP)A signaling protocol (IP protocol 46) that reserves resources along a path, used by IntServ and MPLS TE.Advanced
• RIB GroupA Junos mechanism to install routes from a protocol or interface into multiple routing tables simultaneously.Advanced
• Route Distinguisher (RD)A 64-bit value prepended to an IPv4 prefix to make it a unique VPNv4 route, allowing overlapping customer addresses.Advanced
• Route PreferenceJunos term for administrative distance: a 0-4294967295 value where the lower preference wins between route sources.Intermediate
• Route Target (RT)A BGP extended community that controls which VRFs export and import VPN routes, enabling topologies like hub-and-spoke and extranet.Advanced
• Routing Engine (RE)The Junos control plane component that runs routing protocols, the CLI and management, and builds the forwarding table.Foundational
• Routing InstanceA Junos construct that creates a separate routing table and set of interfaces, with types including virtual-router, vrf, forwarding and evpn/mac-vrf.Intermediate
• RSVP-TERSVP extensions used to signal MPLS TE LSPs with explicit routes, bandwidth reservations and label distribution.Advanced
• Segment Identifier (SID)An identifier for a segment: an MPLS label in SR-MPLS or an IPv6 address in SRv6.Advanced
• Segment Routing (SR)A source-routing architecture where the ingress node encodes a path as an ordered list of segments, with no per-flow state in the core.Advanced
• Segment Routing Global Block (SRGB)The label range reserved on each router for global SR-MPLS prefix SIDs, default 16000-23999 on Cisco.Advanced
• Segment Routing Header (SRH)An IPv6 routing extension header (routing type 4) that lists SRv6 segments and a Segments Left pointer.Advanced
• Segment Routing Traffic Engineering (SR-TE)Traffic engineering using SR policies identified by headend, color and endpoint, steering traffic onto explicit or dynamic segment lists.Advanced
• SR-MPLSSegment routing using the MPLS data plane, where each segment is an MPLS label.Advanced
• SRv6Segment routing over the IPv6 data plane, where segments are IPv6 addresses carried in the destination address and optional Segment Routing Header.Advanced
• System IDThe 6-byte field in an IS-IS NET that uniquely identifies a router within the routing domain.Advanced
• Targeted LDP (T-LDP)An LDP session between non-adjacent routers using unicast hellos, used for pseudowires and remote LFA.Advanced
• Topology-Independent Loop-Free Alternate (TI-LFA)A segment routing fast reroute method that provides 100 percent link, node and SRLG protection using the post-convergence path.Advanced
• Type-Length-Value (TLV)An extensible encoding of a type code, length and value used by IS-IS, LLDP, BGP and other protocols.Advanced
• Virtual Private LAN Service (VPLS)A multipoint Layer 2 VPN that emulates an Ethernet LAN across an MPLS network using a mesh of pseudowires.Advanced
• Virtual Private Wire Service (VPWS)A point-to-point Layer 2 VPN service delivered over pseudowires or EVPN-VPWS.Advanced
• VPNv4 Address FamilyThe MP-BGP address family that carries 12-byte VPN-IPv4 routes (RD + IPv4 prefix) and VPN labels between PEs.Advanced