Juniper JNCIS-ENT: key terms

Flashcards for this exam Juniper JNCIS-ENT guide Class dates

• Adj-RIB-InThe conceptual BGP table holding unprocessed routes received from a specific peer before inbound policy.Advanced
• Aggregate RouteA Junos summary route defined under routing-options aggregate that is active when at least one contributing more-specific route exists.Intermediate
• Aggregated EthernetJuniper Junos link aggregation interface (aeX) that bundles physical links with or without LACP.Intermediate
• Area Border Router (ABR)An OSPF router with interfaces in area 0 and at least one other area, which summarizes routes between them.Intermediate
• AS Path PrependingAdding extra copies of an ASN to the AS_PATH of advertised routes to make a path less attractive to other ASes.Intermediate
• AS_PATH AttributeA well-known mandatory BGP attribute listing the ASNs a route has traversed; used for loop prevention and path length comparison.Intermediate
• Autonomous System (AS)A set of networks under one administrative control with a single routing policy, identified in BGP by an AS number.Foundational
• Autonomous System Boundary Router (ASBR)An OSPF router that redistributes external routes into OSPF, originating Type 5 or Type 7 LSAs.Intermediate
• Autonomous System Number (ASN)A number identifying a BGP autonomous system: 2-byte (1-65535) or 4-byte (up to 4,294,967,295).Intermediate
• 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 Message TypesBGP's message types: OPEN, UPDATE, KEEPALIVE, NOTIFICATION and ROUTE-REFRESH.Intermediate
• BGP MultipathAllowing BGP to install multiple equal paths for a prefix for load sharing.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 Peer GroupA Cisco IOS construct that applies the same outbound policy to many neighbors and generates updates once per group.Intermediate
• 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
• Bootstrap Router (BSR)The standards-based PIMv2 mechanism for distributing RP-to-group mappings hop by hop.Advanced
• 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
• BPDU GuardAn STP feature that errdisables a port if it receives any BPDU, protecting PortFast edge ports.Intermediate
• Class of Service (CoS)The 3-bit Priority Code Point in the 802.1Q tag used for Layer 2 QoS marking (IEEE 802.1p).Foundational
• Designated Router (DR)The OSPF router elected on a multi-access segment to form full adjacencies with all others and originate the Type 2 LSA.Intermediate
• Discard RouteA route that silently drops matching packets, used to anchor aggregates and prevent loops (Junos discard next hop).Intermediate
• Edge PortAn RSTP port connected to an end host that transitions directly to forwarding and generates no topology changes.Intermediate
• Equal-Cost Multipath (ECMP)Installing and load sharing across multiple routes to the same prefix that have identical cost.Intermediate
• External BGP (eBGP)A BGP session between routers in different autonomous systems.Foundational
• 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
• First Hop Redundancy Protocol (FHRP)A class of protocols that provide a redundant default gateway through a shared virtual IP and MAC address.Foundational
• IGMP SnoopingA switch feature that listens to IGMP messages to forward multicast frames only to ports with interested receivers.Intermediate
• Integrated Routing and Bridging (IRB)A logical Layer 3 interface bound to a bridge domain or VLAN, the Junos and EVPN equivalent of an SVI.Intermediate
• 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
• Internal Spanning Tree (IST)MST instance 0, which carries BPDUs for the region and connects it to the Common and Internal Spanning Tree (CIST).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 Commit ModelThe Junos process of validating and activating the candidate configuration with commit, with options such as commit check, commit confirmed and commit at.Foundational
• Junos Default Routing PoliciesBuilt-in Junos policies applied at the end of each protocol's policy chain when no explicit policy accepts or rejects a route.Intermediate
• 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 Policy ChainThe ordered list of policies applied to a protocol, evaluated until a terminating action (accept or reject) is reached, ending with the default policy.Intermediate
• 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
• Link Aggregation Control Protocol (LACP)IEEE 802.3ad/802.1AX protocol that negotiates link aggregation bundles; modes active and passive.Foundational
• Link-State Advertisement (LSA)An OSPF data unit describing a router's links, a network, or external and summary prefixes, flooded to build the LSDB.Intermediate
• Link-State Database (LSDB)The collection of LSAs a link-state router holds, identical among all routers in the same area.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 GuardAn STP feature that stops a non-designated port from becoming designated when BPDUs stop arriving, preventing loops from unidirectional links.Advanced
• MST RegionA group of interconnected switches with identical MST name, revision number and VLAN-to-instance mapping.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
• Multiple Spanning Tree Protocol (MST)IEEE 802.1s, which maps many VLANs to a small number of RSTP-based spanning tree instances.Advanced
• Next-Hop-SelfA BGP neighbor option that rewrites the NEXT_HOP to the router's own address when advertising to iBGP peers.Intermediate
• NEXT_HOP AttributeA well-known mandatory BGP attribute giving the IP address to forward toward for a prefix.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
• Not-So-Stubby Area (NSSA)An OSPF stub-like area that blocks Type 5 LSAs but allows a local ASBR to inject externals as Type 7 LSAs.Advanced
• Open Shortest Path First (OSPF)An open-standard link-state IGP that uses areas, LSAs and Dijkstra's SPF algorithm with a cost metric.Foundational
• OSPF AuthenticationMethods for authenticating OSPF packets: null, plaintext, MD5 and HMAC-SHA with key chains.Intermediate
• OSPF External Route TypeOSPF E1 and E2 routes: E2 (default) keeps only the redistributed metric, while E1 adds internal cost to reach the ASBR.Intermediate
• OSPF MTU MismatchA condition where OSPF neighbors have different interface MTUs, leaving the adjacency stuck in ExStart or Exchange.Intermediate
• OSPF Neighbor StatesThe progression an OSPF adjacency follows: Down, Attempt, Init, 2-Way, ExStart, Exchange, Loading, Full.Intermediate
• OSPF Stub AreaAn OSPF area that blocks Type 4 and Type 5 external LSAs and receives a default route from the ABR instead.Intermediate
• OSPF Stub Router AdvertisementOSPF max-metric router-lsa: advertising maximum link cost so other routers avoid transiting this router.Advanced
• OSPF Totally Stubby AreaA Cisco OSPF area type that blocks Type 3, 4 and 5 LSAs, leaving only a default route from the ABR.Intermediate
• OSPF Type 1 Router LSAThe LSA every OSPF router originates in each area, describing its links, costs and neighbors; flooded within the area only.Intermediate
• OSPF Type 2 Network LSAThe LSA originated by the DR on a multi-access segment, listing all routers attached to that transit network.Intermediate
• OSPF Type 3 Summary LSAThe LSA an ABR originates to advertise prefixes from one area into another.Intermediate
• OSPF Type 5 External LSAAn LSA originated by an ASBR to advertise routes redistributed from outside OSPF, flooded throughout all normal areas.Intermediate
• OSPF Type 7 NSSA LSAAn external LSA originated by an ASBR inside an NSSA, converted to Type 5 by the NSSA ABR.Advanced
• OSPF Virtual LinkA logical link through a transit area that connects a remote area or partitioned backbone to area 0.Advanced
• OSPFv3The version of OSPF for IPv6 (and, with address families, IPv4) defined in RFC 5340.Intermediate
• Packet Forwarding Engine (PFE)The Junos data plane component, usually ASIC based, that forwards transit traffic using the forwarding table and applies filters, policers and CoS.Foundational
• Path-Vector Routing ProtocolA routing protocol class that advertises the full sequence of autonomous systems a route has traversed, used for loop prevention.Intermediate
• PIM Sparse Mode (PIM-SM)A pull-model multicast protocol where routers explicitly join a shared tree rooted at a rendezvous point and may switch to a source tree.Intermediate
• PolicingA QoS action that enforces a rate limit by dropping or remarking traffic that exceeds it, without buffering.Foundational
• Proposal and AgreementThe RSTP handshake on point-to-point links that lets a designated port move to forwarding immediately.Advanced
• Protocol Independent Multicast (PIM)The family of multicast routing protocols that build distribution trees using the existing unicast routing table for RPF checks.Intermediate
• Rapid Spanning Tree Protocol (RSTP)IEEE 802.1w, a faster STP that uses proposal/agreement handshakes, edge ports and alternate ports to converge in seconds or less.Intermediate
• Rendezvous Point (RP)The PIM-SM router where sources and receivers meet; it roots the shared tree for a group.Intermediate
• Reverse Path Forwarding Check (RPF)The multicast loop-prevention check that accepts a packet only if it arrives on the interface the router would use to reach the source (or RP).Intermediate
• RIB GroupA Junos mechanism to install routes from a protocol or interface into multiple routing tables simultaneously.Advanced
• Root GuardAn STP feature that prevents a port from becoming a root port; superior BPDUs place it in root-inconsistent state.Intermediate
• Route FilterA Junos policy match condition that selects routes by prefix and match type: exact, orlonger, longer, upto, through and prefix-length-range.Intermediate
• Route PreferenceJunos term for administrative distance: a 0-4294967295 value where the lower preference wins between route sources.Intermediate
• Route RedistributionInjecting routes learned from one routing source into another routing protocol.Intermediate
• Route SummarizationAdvertising a single aggregate prefix that covers multiple more specific routes to reduce table size and contain instability.Intermediate
• Route TagA numeric label attached to a route that carries through redistribution and can be matched by policy.Intermediate
• 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
• Source-Specific Multicast (SSM)A PIM mode in which receivers join a specific (S,G) channel directly, eliminating the RP and shared tree.Intermediate
• Two-Rate Three-Color Marker (trTCM)A policer (RFC 2698) with CIR and PIR that colors traffic conform (green), exceed (yellow) or violate (red).Advanced
• Update-SourceA BGP neighbor option that sets the source interface (usually a loopback) for the TCP session.Intermediate
• Virtual ChassisJuniper technology that interconnects multiple EX or QFX switches to be managed as a single logical device.Intermediate
• Virtual Router Redundancy Protocol (VRRP)IETF-standard FHRP (RFC 5798 for VRRPv3) with one master and backups sharing a virtual IP that may be a real interface address.Foundational
• Virtual Routing and Forwarding (VRF)A technology that creates multiple independent routing tables on one router so overlapping or separated networks coexist.Intermediate
• Zero-Touch Provisioning (ZTP)Automated onboarding where a new device obtains configuration and software from a server without manual console work.Intermediate