JNCIS-DC flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

EVPN Route Type 2

MAC/IP Advertisement route. Carries a host MAC (and optionally IP) with its VNI and next-hop VTEP, letting remote leafs install the MAC-to-VTEP mapping without flooding.

EVPN Route Type 3

Inclusive Multicast Ethernet Tag route. Signals which VTEPs want BUM traffic for a given VNI, building the ingress-replication or multicast tree used to flood broadcasts and unknown unicast.

EVPN Route Type 5

IP Prefix route. Advertises an IP subnet (not a host MAC) with a VNI, enabling L3 symmetric routing across the VXLAN overlay without per-host MAC entries.

VXLAN VNI size

A 24-bit VXLAN Network Identifier, giving roughly 16.7 million segments. It is carried in the VXLAN header and mapped to a VLAN or bridge domain on the VTEP.

VTEP

VXLAN Tunnel Endpoint. The loopback-addressed entity that encapsulates and decapsulates VXLAN frames. If the VTEP source loopback is unreachable, tunnels fail.

ESI multihoming

Ethernet Segment Identifier shared by two leafs attached to the same server. It enables all-active multihoming and per-VLAN designated forwarder election without MC-LAG.

Designated forwarder (DF)

In EVPN multihoming, the leaf elected per Ethernet segment and VLAN that forwards BUM traffic to the multihomed CE. Election uses route type 4 and per-VLAN hashing.

Apstra blueprint

The logical model of a DC fabric in Juniper Apstra: topology, device roles, and intent. Committing and deploying a blueprint renders and pushes device configurations.

Intent-Based Analytics

Apstra IBA probes that continuously validate live telemetry against declared intent, surfacing anomalies when fabric behavior deviates from the intended design.

Junos commit confirmed

commit confirmed N applies the config but auto-rolls back after N minutes unless you run commit again. It protects against locking yourself out with a bad change.

Junos rollback command

rollback N loads the Nth prior committed configuration into the candidate; rollback 0 returns to the running config. Follow with commit to activate.

commit check

Validates the candidate configuration syntax and semantics without applying it or starting the rollback timer. Use it before commit on risky changes.

VLAN-to-VNI mapping

Junos config binding a VLAN to a VXLAN segment: set vlans V100 vlan-id 100 and set vlans V100 vxlan vni 10100, plus switch-options vtep-source-interface.

BGP EVPN family

The BGP address family that carries EVPN routes. On Junos, add family evpn signaling to the iBGP group; route reflectors then reflect type 2, 3, and 5 routes.

show evpn database

Junos command listing learned MAC/IP entries with their VNI, VTEP next-hop, and origin (local or remote). First stop when a remote host is unreachable.

bgp.evpn.0 table

The Junos routing table holding received EVPN routes. show route table bgp.evpn.0 confirms whether type 2/3/5 routes arrived from the route reflector.

ESI interface config

Junos: set interfaces ae0 esi <10-byte value> and set interfaces ae0 esi all-active. Both leafs use the same ESI for a multihomed server.

Ingress replication

VXLAN BUM handling where the ingress VTEP replicates frames to every VTEP in the type 3 list. Alternative to underlay multicast; configured with protocols evpn multicast-mode ingress-replication.

Interface range

Junos construct grouping physical interfaces under one name so shared config is applied once, e.g. set interfaces interface-range LEAF member ge-0/0/[0-23].

apply-groups

Junos inheritance mechanism: common configuration in a group is merged into every member that references it, reducing repetition across many interfaces or protocols.

Spine-leaf topology

Two-tier DC design where every leaf connects to every spine. Any-to-any server traffic is at most two hops, and the underlay uses ECMP for load spreading.

Oversubscription ratio

Southbound (server-facing) bandwidth divided by northbound (uplink) bandwidth. A 3:1 access-to-spine ratio is common; 1:1 is used where east-west traffic dominates.

ECMP hash key

Fields used to pick an ECMP next-hop. Junos defaults to layer-3; enabling layer-4 adds source/destination ports so flows spread more evenly across uplinks.

Jumbo MTU

Frame size above 1500 bytes, typically 9216 on DC links. It must be consistent end-to-end or large packets drop silently; set with interfaces mtu 9216.

Storm control

Per-port limits on broadcast, multicast, and unknown-unicast traffic expressed as bandwidth percentage. Prevents a loop or misbehaving host from saturating the fabric.

GRES

Graceful Routing Engine Switchover. On dual-RE Junos devices, forwarding continues during a routing-engine failover because kernel state is synchronized to the backup RE.

NSR

Nonstop Routing. Keeps routing protocol adjacencies and state alive across a routing-engine switchover, so peers do not see a reset. Requires GRES.

MC-LAG ICCP

Inter-Chassis Control Protocol link between two MC-LAG peers, plus a backup liveness link. Together they present one LAG to the server and coordinate forwarding state.

Junos PyEZ

Python library for Junos automation. Device(host, user, password).open() then RPC calls such as get_interface_information; maps Python methods to Junos RPCs.

NETCONF port

TCP 830, running over SSH. Junos exposes YANG-modeled configuration through NETCONF get-config and edit-config operations for controller and script integration.

load override

Junos load operation replacing the entire candidate configuration with the loaded file. Contrast with load merge, which adds to the existing hierarchy.

ZTP DHCP options

DHCP options (boot-file-name or option 43) tell a factory switch where to fetch its Junos image and config during zero touch provisioning.